remove lib/libsqlite3, it has moved back to ports

1 files changed, 0 insertions, 7289 deletions

diff --git a/lib/libsqlite3/src/pager.c b/lib/libsqlite3/src/pager.c
deleted file mode 100644
index 399070af01d..00000000000
--- a/lib/libsqlite3/src/pager.c
+++ /dev/null
@@ -1,7289 +0,0 @@
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This is the implementation of the page cache subsystem or "pager".
-** 
-** The pager is used to access a database disk file.  It implements
-** atomic commit and rollback through the use of a journal file that
-** is separate from the database file.  The pager also implements file
-** locking to prevent two processes from writing the same database
-** file simultaneously, or one process from reading the database while
-** another is writing.
-*/
-#ifndef SQLITE_OMIT_DISKIO
-#include "sqliteInt.h"
-#include "wal.h"
-
-
-/******************* NOTES ON THE DESIGN OF THE PAGER ************************
-**
-** This comment block describes invariants that hold when using a rollback
-** journal.  These invariants do not apply for journal_mode=WAL,
-** journal_mode=MEMORY, or journal_mode=OFF.
-**
-** Within this comment block, a page is deemed to have been synced
-** automatically as soon as it is written when PRAGMA synchronous=OFF.
-** Otherwise, the page is not synced until the xSync method of the VFS
-** is called successfully on the file containing the page.
-**
-** Definition:  A page of the database file is said to be "overwriteable" if
-** one or more of the following are true about the page:
-** 
-**     (a)  The original content of the page as it was at the beginning of
-**          the transaction has been written into the rollback journal and
-**          synced.
-** 
-**     (b)  The page was a freelist leaf page at the start of the transaction.
-** 
-**     (c)  The page number is greater than the largest page that existed in
-**          the database file at the start of the transaction.
-** 
-** (1) A page of the database file is never overwritten unless one of the
-**     following are true:
-** 
-**     (a) The page and all other pages on the same sector are overwriteable.
-** 
-**     (b) The atomic page write optimization is enabled, and the entire
-**         transaction other than the update of the transaction sequence
-**         number consists of a single page change.
-** 
-** (2) The content of a page written into the rollback journal exactly matches
-**     both the content in the database when the rollback journal was written
-**     and the content in the database at the beginning of the current
-**     transaction.
-** 
-** (3) Writes to the database file are an integer multiple of the page size
-**     in length and are aligned on a page boundary.
-** 
-** (4) Reads from the database file are either aligned on a page boundary and
-**     an integer multiple of the page size in length or are taken from the
-**     first 100 bytes of the database file.
-** 
-** (5) All writes to the database file are synced prior to the rollback journal
-**     being deleted, truncated, or zeroed.
-** 
-** (6) If a master journal file is used, then all writes to the database file
-**     are synced prior to the master journal being deleted.
-** 
-** Definition: Two databases (or the same database at two points it time)
-** are said to be "logically equivalent" if they give the same answer to
-** all queries.  Note in particular the content of freelist leaf
-** pages can be changed arbitrarily without affecting the logical equivalence
-** of the database.
-** 
-** (7) At any time, if any subset, including the empty set and the total set,
-**     of the unsynced changes to a rollback journal are removed and the 
-**     journal is rolled back, the resulting database file will be logically
-**     equivalent to the database file at the beginning of the transaction.
-** 
-** (8) When a transaction is rolled back, the xTruncate method of the VFS
-**     is called to restore the database file to the same size it was at
-**     the beginning of the transaction.  (In some VFSes, the xTruncate
-**     method is a no-op, but that does not change the fact the SQLite will
-**     invoke it.)
-** 
-** (9) Whenever the database file is modified, at least one bit in the range
-**     of bytes from 24 through 39 inclusive will be changed prior to releasing
-**     the EXCLUSIVE lock, thus signaling other connections on the same
-**     database to flush their caches.
-**
-** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less
-**      than one billion transactions.
-**
-** (11) A database file is well-formed at the beginning and at the conclusion
-**      of every transaction.
-**
-** (12) An EXCLUSIVE lock is held on the database file when writing to
-**      the database file.
-**
-** (13) A SHARED lock is held on the database file while reading any
-**      content out of the database file.
-**
-******************************************************************************/
-
-/*
-** Macros for troubleshooting.  Normally turned off
-*/
-#if 0
-int sqlite3PagerTrace=1;  /* True to enable tracing */
-#define sqlite3DebugPrintf printf
-#define PAGERTRACE(X)     if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; }
-#else
-#define PAGERTRACE(X)
-#endif
-
-/*
-** The following two macros are used within the PAGERTRACE() macros above
-** to print out file-descriptors. 
-**
-** PAGERID() takes a pointer to a Pager struct as its argument. The
-** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file
-** struct as its argument.
-*/
-#define PAGERID(p) ((int)(p->fd))
-#define FILEHANDLEID(fd) ((int)fd)
-
-/*
-** The Pager.eState variable stores the current 'state' of a pager. A
-** pager may be in any one of the seven states shown in the following
-** state diagram.
-**
-**                            OPEN <------+------+
-**                              |         |      |
-**                              V         |      |
-**               +---------> READER-------+      |
-**               |              |                |
-**               |              V                |
-**               |<-------WRITER_LOCKED------> ERROR
-**               |              |                ^  
-**               |              V                |
-**               |<------WRITER_CACHEMOD-------->|
-**               |              |                |
-**               |              V                |
-**               |<-------WRITER_DBMOD---------->|
-**               |              |                |
-**               |              V                |
-**               +<------WRITER_FINISHED-------->+
-**
-**
-** List of state transitions and the C [function] that performs each:
-** 
-**   OPEN              -> READER              [sqlite3PagerSharedLock]
-**   READER            -> OPEN                [pager_unlock]
-**
-**   READER            -> WRITER_LOCKED       [sqlite3PagerBegin]
-**   WRITER_LOCKED     -> WRITER_CACHEMOD     [pager_open_journal]
-**   WRITER_CACHEMOD   -> WRITER_DBMOD        [syncJournal]
-**   WRITER_DBMOD      -> WRITER_FINISHED     [sqlite3PagerCommitPhaseOne]
-**   WRITER_***        -> READER              [pager_end_transaction]
-**
-**   WRITER_***        -> ERROR               [pager_error]
-**   ERROR             -> OPEN                [pager_unlock]
-** 
-**
-**  OPEN:
-**
-**    The pager starts up in this state. Nothing is guaranteed in this
-**    state - the file may or may not be locked and the database size is
-**    unknown. The database may not be read or written.
-**
-**    * No read or write transaction is active.
-**    * Any lock, or no lock at all, may be held on the database file.
-**    * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
-**
-**  READER:
-**
-**    In this state all the requirements for reading the database in 
-**    rollback (non-WAL) mode are met. Unless the pager is (or recently
-**    was) in exclusive-locking mode, a user-level read transaction is 
-**    open. The database size is known in this state.
-**
-**    A connection running with locking_mode=normal enters this state when
-**    it opens a read-transaction on the database and returns to state
-**    OPEN after the read-transaction is completed. However a connection
-**    running in locking_mode=exclusive (including temp databases) remains in
-**    this state even after the read-transaction is closed. The only way
-**    a locking_mode=exclusive connection can transition from READER to OPEN
-**    is via the ERROR state (see below).
-** 
-**    * A read transaction may be active (but a write-transaction cannot).
-**    * A SHARED or greater lock is held on the database file.
-**    * The dbSize variable may be trusted (even if a user-level read 
-**      transaction is not active). The dbOrigSize and dbFileSize variables
-**      may not be trusted at this point.
-**    * If the database is a WAL database, then the WAL connection is open.
-**    * Even if a read-transaction is not open, it is guaranteed that 
-**      there is no hot-journal in the file-system.
-**
-**  WRITER_LOCKED:
-**
-**    The pager moves to this state from READER when a write-transaction
-**    is first opened on the database. In WRITER_LOCKED state, all locks 
-**    required to start a write-transaction are held, but no actual 
-**    modifications to the cache or database have taken place.
-**
-**    In rollback mode, a RESERVED or (if the transaction was opened with 
-**    BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when
-**    moving to this state, but the journal file is not written to or opened 
-**    to in this state. If the transaction is committed or rolled back while 
-**    in WRITER_LOCKED state, all that is required is to unlock the database 
-**    file.
-**
-**    IN WAL mode, WalBeginWriteTransaction() is called to lock the log file.
-**    If the connection is running with locking_mode=exclusive, an attempt
-**    is made to obtain an EXCLUSIVE lock on the database file.
-**
-**    * A write transaction is active.
-**    * If the connection is open in rollback-mode, a RESERVED or greater 
-**      lock is held on the database file.
-**    * If the connection is open in WAL-mode, a WAL write transaction
-**      is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully
-**      called).
-**    * The dbSize, dbOrigSize and dbFileSize variables are all valid.
-**    * The contents of the pager cache have not been modified.
-**    * The journal file may or may not be open.
-**    * Nothing (not even the first header) has been written to the journal.
-**
-**  WRITER_CACHEMOD:
-**
-**    A pager moves from WRITER_LOCKED state to this state when a page is
-**    first modified by the upper layer. In rollback mode the journal file
-**    is opened (if it is not already open) and a header written to the
-**    start of it. The database file on disk has not been modified.
-**
-**    * A write transaction is active.
-**    * A RESERVED or greater lock is held on the database file.
-**    * The journal file is open and the first header has been written 
-**      to it, but the header has not been synced to disk.
-**    * The contents of the page cache have been modified.
-**
-**  WRITER_DBMOD:
-**
-**    The pager transitions from WRITER_CACHEMOD into WRITER_DBMOD state
-**    when it modifies the contents of the database file. WAL connections
-**    never enter this state (since they do not modify the database file,
-**    just the log file).
-**
-**    * A write transaction is active.
-**    * An EXCLUSIVE or greater lock is held on the database file.
-**    * The journal file is open and the first header has been written 
-**      and synced to disk.
-**    * The contents of the page cache have been modified (and possibly
-**      written to disk).
-**
-**  WRITER_FINISHED:
-**
-**    It is not possible for a WAL connection to enter this state.
-**
-**    A rollback-mode pager changes to WRITER_FINISHED state from WRITER_DBMOD
-**    state after the entire transaction has been successfully written into the
-**    database file. In this state the transaction may be committed simply
-**    by finalizing the journal file. Once in WRITER_FINISHED state, it is 
-**    not possible to modify the database further. At this point, the upper 
-**    layer must either commit or rollback the transaction.
-**
-**    * A write transaction is active.
-**    * An EXCLUSIVE or greater lock is held on the database file.
-**    * All writing and syncing of journal and database data has finished.
-**      If no error occurred, all that remains is to finalize the journal to
-**      commit the transaction. If an error did occur, the caller will need
-**      to rollback the transaction. 
-**
-**  ERROR:
-**
-**    The ERROR state is entered when an IO or disk-full error (including
-**    SQLITE_IOERR_NOMEM) occurs at a point in the code that makes it 
-**    difficult to be sure that the in-memory pager state (cache contents, 
-**    db size etc.) are consistent with the contents of the file-system.
-**
-**    Temporary pager files may enter the ERROR state, but in-memory pagers
-**    cannot.
-**
-**    For example, if an IO error occurs while performing a rollback, 
-**    the contents of the page-cache may be left in an inconsistent state.
-**    At this point it would be dangerous to change back to READER state
-**    (as usually happens after a rollback). Any subsequent readers might
-**    report database corruption (due to the inconsistent cache), and if
-**    they upgrade to writers, they may inadvertently corrupt the database
-**    file. To avoid this hazard, the pager switches into the ERROR state
-**    instead of READER following such an error.
-**
-**    Once it has entered the ERROR state, any attempt to use the pager
-**    to read or write data returns an error. Eventually, once all 
-**    outstanding transactions have been abandoned, the pager is able to
-**    transition back to OPEN state, discarding the contents of the 
-**    page-cache and any other in-memory state at the same time. Everything
-**    is reloaded from disk (and, if necessary, hot-journal rollback peformed)
-**    when a read-transaction is next opened on the pager (transitioning
-**    the pager into READER state). At that point the system has recovered 
-**    from the error.
-**
-**    Specifically, the pager jumps into the ERROR state if:
-**
-**      1. An error occurs while attempting a rollback. This happens in
-**         function sqlite3PagerRollback().
-**
-**      2. An error occurs while attempting to finalize a journal file
-**         following a commit in function sqlite3PagerCommitPhaseTwo().
-**
-**      3. An error occurs while attempting to write to the journal or
-**         database file in function pagerStress() in order to free up
-**         memory.
-**
-**    In other cases, the error is returned to the b-tree layer. The b-tree
-**    layer then attempts a rollback operation. If the error condition 
-**    persists, the pager enters the ERROR state via condition (1) above.
-**
-**    Condition (3) is necessary because it can be triggered by a read-only
-**    statement executed within a transaction. In this case, if the error
-**    code were simply returned to the user, the b-tree layer would not
-**    automatically attempt a rollback, as it assumes that an error in a
-**    read-only statement cannot leave the pager in an internally inconsistent 
-**    state.
-**
-**    * The Pager.errCode variable is set to something other than SQLITE_OK.
-**    * There are one or more outstanding references to pages (after the
-**      last reference is dropped the pager should move back to OPEN state).
-**    * The pager is not an in-memory pager.
-**    
-**
-** Notes:
-**
-**   * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the
-**     connection is open in WAL mode. A WAL connection is always in one
-**     of the first four states.
-**
-**   * Normally, a connection open in exclusive mode is never in PAGER_OPEN
-**     state. There are two exceptions: immediately after exclusive-mode has
-**     been turned on (and before any read or write transactions are 
-**     executed), and when the pager is leaving the "error state".
-**
-**   * See also: assert_pager_state().
-*/
-#define PAGER_OPEN                  0
-#define PAGER_READER                1
-#define PAGER_WRITER_LOCKED         2
-#define PAGER_WRITER_CACHEMOD       3
-#define PAGER_WRITER_DBMOD          4
-#define PAGER_WRITER_FINISHED       5
-#define PAGER_ERROR                 6
-
-/*
-** The Pager.eLock variable is almost always set to one of the 
-** following locking-states, according to the lock currently held on
-** the database file: NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
-** This variable is kept up to date as locks are taken and released by
-** the pagerLockDb() and pagerUnlockDb() wrappers.
-**
-** If the VFS xLock() or xUnlock() returns an error other than SQLITE_BUSY
-** (i.e. one of the SQLITE_IOERR subtypes), it is not clear whether or not
-** the operation was successful. In these circumstances pagerLockDb() and
-** pagerUnlockDb() take a conservative approach - eLock is always updated
-** when unlocking the file, and only updated when locking the file if the
-** VFS call is successful. This way, the Pager.eLock variable may be set
-** to a less exclusive (lower) value than the lock that is actually held
-** at the system level, but it is never set to a more exclusive value.
-**
-** This is usually safe. If an xUnlock fails or appears to fail, there may 
-** be a few redundant xLock() calls or a lock may be held for longer than
-** required, but nothing really goes wrong.
-**
-** The exception is when the database file is unlocked as the pager moves
-** from ERROR to OPEN state. At this point there may be a hot-journal file 
-** in the file-system that needs to be rolled back (as part of an OPEN->SHARED
-** transition, by the same pager or any other). If the call to xUnlock()
-** fails at this point and the pager is left holding an EXCLUSIVE lock, this
-** can confuse the call to xCheckReservedLock() call made later as part
-** of hot-journal detection.
-**
-** xCheckReservedLock() is defined as returning true "if there is a RESERVED 
-** lock held by this process or any others". So xCheckReservedLock may 
-** return true because the caller itself is holding an EXCLUSIVE lock (but
-** doesn't know it because of a previous error in xUnlock). If this happens
-** a hot-journal may be mistaken for a journal being created by an active
-** transaction in another process, causing SQLite to read from the database
-** without rolling it back.
-**
-** To work around this, if a call to xUnlock() fails when unlocking the
-** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It
-** is only changed back to a real locking state after a successful call
-** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition
-** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK 
-** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE
-** lock on the database file before attempting to roll it back. See function
-** PagerSharedLock() for more detail.
-**
-** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in 
-** PAGER_OPEN state.
-*/
-#define UNKNOWN_LOCK                (EXCLUSIVE_LOCK+1)
-
-/*
-** A macro used for invoking the codec if there is one
-*/
-#ifdef SQLITE_HAS_CODEC
-# define CODEC1(P,D,N,X,E) \
-    if( P->xCodec && P->xCodec(P->pCodec,D,N,X)==0 ){ E; }
-# define CODEC2(P,D,N,X,E,O) \
-    if( P->xCodec==0 ){ O=(char*)D; }else \
-    if( (O=(char*)(P->xCodec(P->pCodec,D,N,X)))==0 ){ E; }
-#else
-# define CODEC1(P,D,N,X,E)   /* NO-OP */
-# define CODEC2(P,D,N,X,E,O) O=(char*)D
-#endif
-
-/*
-** The maximum allowed sector size. 64KiB. If the xSectorsize() method 
-** returns a value larger than this, then MAX_SECTOR_SIZE is used instead.
-** This could conceivably cause corruption following a power failure on
-** such a system. This is currently an undocumented limit.
-*/
-#define MAX_SECTOR_SIZE 0x10000
-
-/*
-** An instance of the following structure is allocated for each active
-** savepoint and statement transaction in the system. All such structures
-** are stored in the Pager.aSavepoint[] array, which is allocated and
-** resized using sqlite3Realloc().
-**
-** When a savepoint is created, the PagerSavepoint.iHdrOffset field is
-** set to 0. If a journal-header is written into the main journal while
-** the savepoint is active, then iHdrOffset is set to the byte offset 
-** immediately following the last journal record written into the main
-** journal before the journal-header. This is required during savepoint
-** rollback (see pagerPlaybackSavepoint()).
-*/
-typedef struct PagerSavepoint PagerSavepoint;
-struct PagerSavepoint {
-  i64 iOffset;                 /* Starting offset in main journal */
-  i64 iHdrOffset;              /* See above */
-  Bitvec *pInSavepoint;        /* Set of pages in this savepoint */
-  Pgno nOrig;                  /* Original number of pages in file */
-  Pgno iSubRec;                /* Index of first record in sub-journal */
-#ifndef SQLITE_OMIT_WAL
-  u32 aWalData[WAL_SAVEPOINT_NDATA];        /* WAL savepoint context */
-#endif
-};
-
-/*
-** Bits of the Pager.doNotSpill flag.  See further description below.
-*/
-#define SPILLFLAG_OFF         0x01 /* Never spill cache.  Set via pragma */
-#define SPILLFLAG_ROLLBACK    0x02 /* Current rolling back, so do not spill */
-#define SPILLFLAG_NOSYNC      0x04 /* Spill is ok, but do not sync */
-
-/*
-** An open page cache is an instance of struct Pager. A description of
-** some of the more important member variables follows:
-**
-** eState
-**
-**   The current 'state' of the pager object. See the comment and state
-**   diagram above for a description of the pager state.
-**
-** eLock
-**
-**   For a real on-disk database, the current lock held on the database file -
-**   NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
-**
-**   For a temporary or in-memory database (neither of which require any
-**   locks), this variable is always set to EXCLUSIVE_LOCK. Since such
-**   databases always have Pager.exclusiveMode==1, this tricks the pager
-**   logic into thinking that it already has all the locks it will ever
-**   need (and no reason to release them).
-**
-**   In some (obscure) circumstances, this variable may also be set to
-**   UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for
-**   details.
-**
-** changeCountDone
-**
-**   This boolean variable is used to make sure that the change-counter 
-**   (the 4-byte header field at byte offset 24 of the database file) is 
-**   not updated more often than necessary. 
-**
-**   It is set to true when the change-counter field is updated, which 
-**   can only happen if an exclusive lock is held on the database file.
-**   It is cleared (set to false) whenever an exclusive lock is 
-**   relinquished on the database file. Each time a transaction is committed,
-**   The changeCountDone flag is inspected. If it is true, the work of
-**   updating the change-counter is omitted for the current transaction.
-**
-**   This mechanism means that when running in exclusive mode, a connection 
-**   need only update the change-counter once, for the first transaction
-**   committed.
-**
-** setMaster
-**
-**   When PagerCommitPhaseOne() is called to commit a transaction, it may
-**   (or may not) specify a master-journal name to be written into the 
-**   journal file before it is synced to disk.
-**
-**   Whether or not a journal file contains a master-journal pointer affects 
-**   the way in which the journal file is finalized after the transaction is 
-**   committed or rolled back when running in "journal_mode=PERSIST" mode.
-**   If a journal file does not contain a master-journal pointer, it is
-**   finalized by overwriting the first journal header with zeroes. If
-**   it does contain a master-journal pointer the journal file is finalized 
-**   by truncating it to zero bytes, just as if the connection were 
-**   running in "journal_mode=truncate" mode.
-**
-**   Journal files that contain master journal pointers cannot be finalized
-**   simply by overwriting the first journal-header with zeroes, as the
-**   master journal pointer could interfere with hot-journal rollback of any
-**   subsequently interrupted transaction that reuses the journal file.
-**
-**   The flag is cleared as soon as the journal file is finalized (either
-**   by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
-**   journal file from being successfully finalized, the setMaster flag
-**   is cleared anyway (and the pager will move to ERROR state).
-**
-** doNotSpill
-**
-**   This variables control the behavior of cache-spills  (calls made by
-**   the pcache module to the pagerStress() routine to write cached data
-**   to the file-system in order to free up memory).
-**
-**   When bits SPILLFLAG_OFF or SPILLFLAG_ROLLBACK of doNotSpill are set,
-**   writing to the database from pagerStress() is disabled altogether.
-**   The SPILLFLAG_ROLLBACK case is done in a very obscure case that
-**   comes up during savepoint rollback that requires the pcache module
-**   to allocate a new page to prevent the journal file from being written
-**   while it is being traversed by code in pager_playback().  The SPILLFLAG_OFF
-**   case is a user preference.
-** 
-**   If the SPILLFLAG_NOSYNC bit is set, writing to the database from
-**   pagerStress() is permitted, but syncing the journal file is not.
-**   This flag is set by sqlite3PagerWrite() when the file-system sector-size
-**   is larger than the database page-size in order to prevent a journal sync
-**   from happening in between the journalling of two pages on the same sector. 
-**
-** subjInMemory
-**
-**   This is a boolean variable. If true, then any required sub-journal
-**   is opened as an in-memory journal file. If false, then in-memory
-**   sub-journals are only used for in-memory pager files.
-**
-**   This variable is updated by the upper layer each time a new 
-**   write-transaction is opened.
-**
-** dbSize, dbOrigSize, dbFileSize
-**
-**   Variable dbSize is set to the number of pages in the database file.
-**   It is valid in PAGER_READER and higher states (all states except for
-**   OPEN and ERROR). 
-**
-**   dbSize is set based on the size of the database file, which may be 
-**   larger than the size of the database (the value stored at offset
-**   28 of the database header by the btree). If the size of the file
-**   is not an integer multiple of the page-size, the value stored in
-**   dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2).
-**   Except, any file that is greater than 0 bytes in size is considered
-**   to have at least one page. (i.e. a 1KB file with 2K page-size leads
-**   to dbSize==1).
-**
-**   During a write-transaction, if pages with page-numbers greater than
-**   dbSize are modified in the cache, dbSize is updated accordingly.
-**   Similarly, if the database is truncated using PagerTruncateImage(), 
-**   dbSize is updated.
-**
-**   Variables dbOrigSize and dbFileSize are valid in states 
-**   PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize
-**   variable at the start of the transaction. It is used during rollback,
-**   and to determine whether or not pages need to be journalled before
-**   being modified.
-**
-**   Throughout a write-transaction, dbFileSize contains the size of
-**   the file on disk in pages. It is set to a copy of dbSize when the
-**   write-transaction is first opened, and updated when VFS calls are made
-**   to write or truncate the database file on disk. 
-**
-**   The only reason the dbFileSize variable is required is to suppress 
-**   unnecessary calls to xTruncate() after committing a transaction. If, 
-**   when a transaction is committed, the dbFileSize variable indicates 
-**   that the database file is larger than the database image (Pager.dbSize), 
-**   pager_truncate() is called. The pager_truncate() call uses xFilesize()
-**   to measure the database file on disk, and then truncates it if required.
-**   dbFileSize is not used when rolling back a transaction. In this case
-**   pager_truncate() is called unconditionally (which means there may be
-**   a call to xFilesize() that is not strictly required). In either case,
-**   pager_truncate() may cause the file to become smaller or larger.
-**
-** dbHintSize
-**
-**   The dbHintSize variable is used to limit the number of calls made to
-**   the VFS xFileControl(FCNTL_SIZE_HINT) method. 
-**
-**   dbHintSize is set to a copy of the dbSize variable when a
-**   write-transaction is opened (at the same time as dbFileSize and
-**   dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called,
-**   dbHintSize is increased to the number of pages that correspond to the
-**   size-hint passed to the method call. See pager_write_pagelist() for 
-**   details.
-**
-** errCode
-**
-**   The Pager.errCode variable is only ever used in PAGER_ERROR state. It
-**   is set to zero in all other states. In PAGER_ERROR state, Pager.errCode 
-**   is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX 
-**   sub-codes.
-*/
-struct Pager {
-  sqlite3_vfs *pVfs;          /* OS functions to use for IO */
-  u8 exclusiveMode;           /* Boolean. True if locking_mode==EXCLUSIVE */
-  u8 journalMode;             /* One of the PAGER_JOURNALMODE_* values */
-  u8 useJournal;              /* Use a rollback journal on this file */
-  u8 noSync;                  /* Do not sync the journal if true */
-  u8 fullSync;                /* Do extra syncs of the journal for robustness */
-  u8 ckptSyncFlags;           /* SYNC_NORMAL or SYNC_FULL for checkpoint */
-  u8 walSyncFlags;            /* SYNC_NORMAL or SYNC_FULL for wal writes */
-  u8 syncFlags;               /* SYNC_NORMAL or SYNC_FULL otherwise */
-  u8 tempFile;                /* zFilename is a temporary or immutable file */
-  u8 noLock;                  /* Do not lock (except in WAL mode) */
-  u8 readOnly;                /* True for a read-only database */
-  u8 memDb;                   /* True to inhibit all file I/O */
-
-  /**************************************************************************
-  ** The following block contains those class members that change during
-  ** routine operation.  Class members not in this block are either fixed
-  ** when the pager is first created or else only change when there is a
-  ** significant mode change (such as changing the page_size, locking_mode,
-  ** or the journal_mode).  From another view, these class members describe
-  ** the "state" of the pager, while other class members describe the
-  ** "configuration" of the pager.
-  */
-  u8 eState;                  /* Pager state (OPEN, READER, WRITER_LOCKED..) */
-  u8 eLock;                   /* Current lock held on database file */
-  u8 changeCountDone;         /* Set after incrementing the change-counter */
-  u8 setMaster;               /* True if a m-j name has been written to jrnl */
-  u8 doNotSpill;              /* Do not spill the cache when non-zero */
-  u8 subjInMemory;            /* True to use in-memory sub-journals */
-  u8 bUseFetch;               /* True to use xFetch() */
-  u8 hasHeldSharedLock;       /* True if a shared lock has ever been held */
-  Pgno dbSize;                /* Number of pages in the database */
-  Pgno dbOrigSize;            /* dbSize before the current transaction */
-  Pgno dbFileSize;            /* Number of pages in the database file */
-  Pgno dbHintSize;            /* Value passed to FCNTL_SIZE_HINT call */
-  int errCode;                /* One of several kinds of errors */
-  int nRec;                   /* Pages journalled since last j-header written */
-  u32 cksumInit;              /* Quasi-random value added to every checksum */
-  u32 nSubRec;                /* Number of records written to sub-journal */
-  Bitvec *pInJournal;         /* One bit for each page in the database file */
-  sqlite3_file *fd;           /* File descriptor for database */
-  sqlite3_file *jfd;          /* File descriptor for main journal */
-  sqlite3_file *sjfd;         /* File descriptor for sub-journal */
-  i64 journalOff;             /* Current write offset in the journal file */
-  i64 journalHdr;             /* Byte offset to previous journal header */
-  sqlite3_backup *pBackup;    /* Pointer to list of ongoing backup processes */
-  PagerSavepoint *aSavepoint; /* Array of active savepoints */
-  int nSavepoint;             /* Number of elements in aSavepoint[] */
-  u32 iDataVersion;           /* Changes whenever database content changes */
-  char dbFileVers[16];        /* Changes whenever database file changes */
-
-  int nMmapOut;               /* Number of mmap pages currently outstanding */
-  sqlite3_int64 szMmap;       /* Desired maximum mmap size */
-  PgHdr *pMmapFreelist;       /* List of free mmap page headers (pDirty) */
-  /*
-  ** End of the routinely-changing class members
-  ***************************************************************************/
-
-  u16 nExtra;                 /* Add this many bytes to each in-memory page */
-  i16 nReserve;               /* Number of unused bytes at end of each page */
-  u32 vfsFlags;               /* Flags for sqlite3_vfs.xOpen() */
-  u32 sectorSize;             /* Assumed sector size during rollback */
-  int pageSize;               /* Number of bytes in a page */
-  Pgno mxPgno;                /* Maximum allowed size of the database */
-  i64 journalSizeLimit;       /* Size limit for persistent journal files */
-  char *zFilename;            /* Name of the database file */
-  char *zJournal;             /* Name of the journal file */
-  int (*xBusyHandler)(void*); /* Function to call when busy */
-  void *pBusyHandlerArg;      /* Context argument for xBusyHandler */
-  int aStat[3];               /* Total cache hits, misses and writes */
-#ifdef SQLITE_TEST
-  int nRead;                  /* Database pages read */
-#endif
-  void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
-#ifdef SQLITE_HAS_CODEC
-  void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
-  void (*xCodecSizeChng)(void*,int,int); /* Notify of page size changes */
-  void (*xCodecFree)(void*);             /* Destructor for the codec */
-  void *pCodec;               /* First argument to xCodec... methods */
-#endif
-  char *pTmpSpace;            /* Pager.pageSize bytes of space for tmp use */
-  PCache *pPCache;            /* Pointer to page cache object */
-#ifndef SQLITE_OMIT_WAL
-  Wal *pWal;                  /* Write-ahead log used by "journal_mode=wal" */
-  char *zWal;                 /* File name for write-ahead log */
-#endif
-};
-
-/*
-** Indexes for use with Pager.aStat[]. The Pager.aStat[] array contains
-** the values accessed by passing SQLITE_DBSTATUS_CACHE_HIT, CACHE_MISS 
-** or CACHE_WRITE to sqlite3_db_status().
-*/
-#define PAGER_STAT_HIT   0
-#define PAGER_STAT_MISS  1
-#define PAGER_STAT_WRITE 2
-
-/*
-** The following global variables hold counters used for
-** testing purposes only.  These variables do not exist in
-** a non-testing build.  These variables are not thread-safe.
-*/
-#ifdef SQLITE_TEST
-int sqlite3_pager_readdb_count = 0;    /* Number of full pages read from DB */
-int sqlite3_pager_writedb_count = 0;   /* Number of full pages written to DB */
-int sqlite3_pager_writej_count = 0;    /* Number of pages written to journal */
-# define PAGER_INCR(v)  v++
-#else
-# define PAGER_INCR(v)
-#endif
-
-
-
-/*
-** Journal files begin with the following magic string.  The data
-** was obtained from /dev/random.  It is used only as a sanity check.
-**
-** Since version 2.8.0, the journal format contains additional sanity
-** checking information.  If the power fails while the journal is being
-** written, semi-random garbage data might appear in the journal
-** file after power is restored.  If an attempt is then made
-** to roll the journal back, the database could be corrupted.  The additional
-** sanity checking data is an attempt to discover the garbage in the
-** journal and ignore it.
-**
-** The sanity checking information for the new journal format consists
-** of a 32-bit checksum on each page of data.  The checksum covers both
-** the page number and the pPager->pageSize bytes of data for the page.
-** This cksum is initialized to a 32-bit random value that appears in the
-** journal file right after the header.  The random initializer is important,
-** because garbage data that appears at the end of a journal is likely
-** data that was once in other files that have now been deleted.  If the
-** garbage data came from an obsolete journal file, the checksums might
-** be correct.  But by initializing the checksum to random value which
-** is different for every journal, we minimize that risk.
-*/
-static const unsigned char aJournalMagic[] = {
-  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
-};
-
-/*
-** The size of the of each page record in the journal is given by
-** the following macro.
-*/
-#define JOURNAL_PG_SZ(pPager)  ((pPager->pageSize) + 8)
-
-/*
-** The journal header size for this pager. This is usually the same 
-** size as a single disk sector. See also setSectorSize().
-*/
-#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
-
-/*
-** The macro MEMDB is true if we are dealing with an in-memory database.
-** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set,
-** the value of MEMDB will be a constant and the compiler will optimize
-** out code that would never execute.
-*/
-#ifdef SQLITE_OMIT_MEMORYDB
-# define MEMDB 0
-#else
-# define MEMDB pPager->memDb
-#endif
-
-/*
-** The macro USEFETCH is true if we are allowed to use the xFetch and xUnfetch
-** interfaces to access the database using memory-mapped I/O.
-*/
-#if SQLITE_MAX_MMAP_SIZE>0
-# define USEFETCH(x) ((x)->bUseFetch)
-#else
-# define USEFETCH(x) 0
-#endif
-
-/*
-** The maximum legal page number is (2^31 - 1).
-*/
-#define PAGER_MAX_PGNO 2147483647
-
-/*
-** The argument to this macro is a file descriptor (type sqlite3_file*).
-** Return 0 if it is not open, or non-zero (but not 1) if it is.
-**
-** This is so that expressions can be written as:
-**
-**   if( isOpen(pPager->jfd) ){ ...
-**
-** instead of
-**
-**   if( pPager->jfd->pMethods ){ ...
-*/
-#define isOpen(pFd) ((pFd)->pMethods!=0)
-
-/*
-** Return true if this pager uses a write-ahead log instead of the usual
-** rollback journal. Otherwise false.
-*/
-#ifndef SQLITE_OMIT_WAL
-static int pagerUseWal(Pager *pPager){
-  return (pPager->pWal!=0);
-}
-#else
-# define pagerUseWal(x) 0
-# define pagerRollbackWal(x) 0
-# define pagerWalFrames(v,w,x,y) 0
-# define pagerOpenWalIfPresent(z) SQLITE_OK
-# define pagerBeginReadTransaction(z) SQLITE_OK
-#endif
-
-#ifndef NDEBUG 
-/*
-** Usage:
-**
-**   assert( assert_pager_state(pPager) );
-**
-** This function runs many asserts to try to find inconsistencies in
-** the internal state of the Pager object.
-*/
-static int assert_pager_state(Pager *p){
-  Pager *pPager = p;
-
-  /* State must be valid. */
-  assert( p->eState==PAGER_OPEN
-       || p->eState==PAGER_READER
-       || p->eState==PAGER_WRITER_LOCKED
-       || p->eState==PAGER_WRITER_CACHEMOD
-       || p->eState==PAGER_WRITER_DBMOD
-       || p->eState==PAGER_WRITER_FINISHED
-       || p->eState==PAGER_ERROR
-  );
-
-  /* Regardless of the current state, a temp-file connection always behaves
-  ** as if it has an exclusive lock on the database file. It never updates
-  ** the change-counter field, so the changeCountDone flag is always set.
-  */
-  assert( p->tempFile==0 || p->eLock==EXCLUSIVE_LOCK );
-  assert( p->tempFile==0 || pPager->changeCountDone );
-
-  /* If the useJournal flag is clear, the journal-mode must be "OFF". 
-  ** And if the journal-mode is "OFF", the journal file must not be open.
-  */
-  assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->useJournal );
-  assert( p->journalMode!=PAGER_JOURNALMODE_OFF || !isOpen(p->jfd) );
-
-  /* Check that MEMDB implies noSync. And an in-memory journal. Since 
-  ** this means an in-memory pager performs no IO at all, it cannot encounter 
-  ** either SQLITE_IOERR or SQLITE_FULL during rollback or while finalizing 
-  ** a journal file. (although the in-memory journal implementation may 
-  ** return SQLITE_IOERR_NOMEM while the journal file is being written). It 
-  ** is therefore not possible for an in-memory pager to enter the ERROR 
-  ** state.
-  */
-  if( MEMDB ){
-    assert( p->noSync );
-    assert( p->journalMode==PAGER_JOURNALMODE_OFF 
-         || p->journalMode==PAGER_JOURNALMODE_MEMORY 
-    );
-    assert( p->eState!=PAGER_ERROR && p->eState!=PAGER_OPEN );
-    assert( pagerUseWal(p)==0 );
-  }
-
-  /* If changeCountDone is set, a RESERVED lock or greater must be held
-  ** on the file.
-  */
-  assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK );
-  assert( p->eLock!=PENDING_LOCK );
-
-  switch( p->eState ){
-    case PAGER_OPEN:
-      assert( !MEMDB );
-      assert( pPager->errCode==SQLITE_OK );
-      assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile );
-      break;
-
-    case PAGER_READER:
-      assert( pPager->errCode==SQLITE_OK );
-      assert( p->eLock!=UNKNOWN_LOCK );
-      assert( p->eLock>=SHARED_LOCK );
-      break;
-
-    case PAGER_WRITER_LOCKED:
-      assert( p->eLock!=UNKNOWN_LOCK );
-      assert( pPager->errCode==SQLITE_OK );
-      if( !pagerUseWal(pPager) ){
-        assert( p->eLock>=RESERVED_LOCK );
-      }
-      assert( pPager->dbSize==pPager->dbOrigSize );
-      assert( pPager->dbOrigSize==pPager->dbFileSize );
-      assert( pPager->dbOrigSize==pPager->dbHintSize );
-      assert( pPager->setMaster==0 );
-      break;
-
-    case PAGER_WRITER_CACHEMOD:
-      assert( p->eLock!=UNKNOWN_LOCK );
-      assert( pPager->errCode==SQLITE_OK );
-      if( !pagerUseWal(pPager) ){
-        /* It is possible that if journal_mode=wal here that neither the
-        ** journal file nor the WAL file are open. This happens during
-        ** a rollback transaction that switches from journal_mode=off
-        ** to journal_mode=wal.
-        */
-        assert( p->eLock>=RESERVED_LOCK );
-        assert( isOpen(p->jfd) 
-             || p->journalMode==PAGER_JOURNALMODE_OFF 
-             || p->journalMode==PAGER_JOURNALMODE_WAL 
-        );
-      }
-      assert( pPager->dbOrigSize==pPager->dbFileSize );
-      assert( pPager->dbOrigSize==pPager->dbHintSize );
-      break;
-
-    case PAGER_WRITER_DBMOD:
-      assert( p->eLock==EXCLUSIVE_LOCK );
-      assert( pPager->errCode==SQLITE_OK );
-      assert( !pagerUseWal(pPager) );
-      assert( p->eLock>=EXCLUSIVE_LOCK );
-      assert( isOpen(p->jfd) 
-           || p->journalMode==PAGER_JOURNALMODE_OFF 
-           || p->journalMode==PAGER_JOURNALMODE_WAL 
-      );
-      assert( pPager->dbOrigSize<=pPager->dbHintSize );
-      break;
-
-    case PAGER_WRITER_FINISHED:
-      assert( p->eLock==EXCLUSIVE_LOCK );
-      assert( pPager->errCode==SQLITE_OK );
-      assert( !pagerUseWal(pPager) );
-      assert( isOpen(p->jfd) 
-           || p->journalMode==PAGER_JOURNALMODE_OFF 
-           || p->journalMode==PAGER_JOURNALMODE_WAL 
-      );
-      break;
-
-    case PAGER_ERROR:
-      /* There must be at least one outstanding reference to the pager if
-      ** in ERROR state. Otherwise the pager should have already dropped
-      ** back to OPEN state.
-      */
-      assert( pPager->errCode!=SQLITE_OK );
-      assert( sqlite3PcacheRefCount(pPager->pPCache)>0 );
-      break;
-  }
-
-  return 1;
-}
-#endif /* ifndef NDEBUG */
-
-#ifdef SQLITE_DEBUG 
-/*
-** Return a pointer to a human readable string in a static buffer
-** containing the state of the Pager object passed as an argument. This
-** is intended to be used within debuggers. For example, as an alternative
-** to "print *pPager" in gdb:
-**
-** (gdb) printf "%s", print_pager_state(pPager)
-*/
-static char *print_pager_state(Pager *p){
-  static char zRet[1024];
-
-  sqlite3_snprintf(1024, zRet,
-      "Filename:      %s\n"
-      "State:         %s errCode=%d\n"
-      "Lock:          %s\n"
-      "Locking mode:  locking_mode=%s\n"
-      "Journal mode:  journal_mode=%s\n"
-      "Backing store: tempFile=%d memDb=%d useJournal=%d\n"
-      "Journal:       journalOff=%lld journalHdr=%lld\n"
-      "Size:          dbsize=%d dbOrigSize=%d dbFileSize=%d\n"
-      , p->zFilename
-      , p->eState==PAGER_OPEN            ? "OPEN" :
-        p->eState==PAGER_READER          ? "READER" :
-        p->eState==PAGER_WRITER_LOCKED   ? "WRITER_LOCKED" :
-        p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" :
-        p->eState==PAGER_WRITER_DBMOD    ? "WRITER_DBMOD" :
-        p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" :
-        p->eState==PAGER_ERROR           ? "ERROR" : "?error?"
-      , (int)p->errCode
-      , p->eLock==NO_LOCK         ? "NO_LOCK" :
-        p->eLock==RESERVED_LOCK   ? "RESERVED" :
-        p->eLock==EXCLUSIVE_LOCK  ? "EXCLUSIVE" :
-        p->eLock==SHARED_LOCK     ? "SHARED" :
-        p->eLock==UNKNOWN_LOCK    ? "UNKNOWN" : "?error?"
-      , p->exclusiveMode ? "exclusive" : "normal"
-      , p->journalMode==PAGER_JOURNALMODE_MEMORY   ? "memory" :
-        p->journalMode==PAGER_JOURNALMODE_OFF      ? "off" :
-        p->journalMode==PAGER_JOURNALMODE_DELETE   ? "delete" :
-        p->journalMode==PAGER_JOURNALMODE_PERSIST  ? "persist" :
-        p->journalMode==PAGER_JOURNALMODE_TRUNCATE ? "truncate" :
-        p->journalMode==PAGER_JOURNALMODE_WAL      ? "wal" : "?error?"
-      , (int)p->tempFile, (int)p->memDb, (int)p->useJournal
-      , p->journalOff, p->journalHdr
-      , (int)p->dbSize, (int)p->dbOrigSize, (int)p->dbFileSize
-  );
-
-  return zRet;
-}
-#endif
-
-/*
-** Return true if it is necessary to write page *pPg into the sub-journal.
-** A page needs to be written into the sub-journal if there exists one
-** or more open savepoints for which:
-**
-**   * The page-number is less than or equal to PagerSavepoint.nOrig, and
-**   * The bit corresponding to the page-number is not set in
-**     PagerSavepoint.pInSavepoint.
-*/
-static int subjRequiresPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  PagerSavepoint *p;
-  Pgno pgno = pPg->pgno;
-  int i;
-  for(i=0; i<pPager->nSavepoint; i++){
-    p = &pPager->aSavepoint[i];
-    if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){
-      return 1;
-    }
-  }
-  return 0;
-}
-
-#ifdef SQLITE_DEBUG
-/*
-** Return true if the page is already in the journal file.
-*/
-static int pageInJournal(Pager *pPager, PgHdr *pPg){
-  return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno);
-}
-#endif
-
-/*
-** Read a 32-bit integer from the given file descriptor.  Store the integer
-** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
-** error code is something goes wrong.
-**
-** All values are stored on disk as big-endian.
-*/
-static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){
-  unsigned char ac[4];
-  int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset);
-  if( rc==SQLITE_OK ){
-    *pRes = sqlite3Get4byte(ac);
-  }
-  return rc;
-}
-
-/*
-** Write a 32-bit integer into a string buffer in big-endian byte order.
-*/
-#define put32bits(A,B)  sqlite3Put4byte((u8*)A,B)
-
-
-/*
-** Write a 32-bit integer into the given file descriptor.  Return SQLITE_OK
-** on success or an error code is something goes wrong.
-*/
-static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
-  char ac[4];
-  put32bits(ac, val);
-  return sqlite3OsWrite(fd, ac, 4, offset);
-}
-
-/*
-** Unlock the database file to level eLock, which must be either NO_LOCK
-** or SHARED_LOCK. Regardless of whether or not the call to xUnlock()
-** succeeds, set the Pager.eLock variable to match the (attempted) new lock.
-**
-** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
-** called, do not modify it. See the comment above the #define of 
-** UNKNOWN_LOCK for an explanation of this.
-*/
-static int pagerUnlockDb(Pager *pPager, int eLock){
-  int rc = SQLITE_OK;
-
-  assert( !pPager->exclusiveMode || pPager->eLock==eLock );
-  assert( eLock==NO_LOCK || eLock==SHARED_LOCK );
-  assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 );
-  if( isOpen(pPager->fd) ){
-    assert( pPager->eLock>=eLock );
-    rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock);
-    if( pPager->eLock!=UNKNOWN_LOCK ){
-      pPager->eLock = (u8)eLock;
-    }
-    IOTRACE(("UNLOCK %p %d\n", pPager, eLock))
-  }
-  return rc;
-}
-
-/*
-** Lock the database file to level eLock, which must be either SHARED_LOCK,
-** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the
-** Pager.eLock variable to the new locking state. 
-**
-** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is 
-** called, do not modify it unless the new locking state is EXCLUSIVE_LOCK. 
-** See the comment above the #define of UNKNOWN_LOCK for an explanation 
-** of this.
-*/
-static int pagerLockDb(Pager *pPager, int eLock){
-  int rc = SQLITE_OK;
-
-  assert( eLock==SHARED_LOCK || eLock==RESERVED_LOCK || eLock==EXCLUSIVE_LOCK );
-  if( pPager->eLock<eLock || pPager->eLock==UNKNOWN_LOCK ){
-    rc = pPager->noLock ? SQLITE_OK : sqlite3OsLock(pPager->fd, eLock);
-    if( rc==SQLITE_OK && (pPager->eLock!=UNKNOWN_LOCK||eLock==EXCLUSIVE_LOCK) ){
-      pPager->eLock = (u8)eLock;
-      IOTRACE(("LOCK %p %d\n", pPager, eLock))
-    }
-  }
-  return rc;
-}
-
-/*
-** This function determines whether or not the atomic-write optimization
-** can be used with this pager. The optimization can be used if:
-**
-**  (a) the value returned by OsDeviceCharacteristics() indicates that
-**      a database page may be written atomically, and
-**  (b) the value returned by OsSectorSize() is less than or equal
-**      to the page size.
-**
-** The optimization is also always enabled for temporary files. It is
-** an error to call this function if pPager is opened on an in-memory
-** database.
-**
-** If the optimization cannot be used, 0 is returned. If it can be used,
-** then the value returned is the size of the journal file when it
-** contains rollback data for exactly one page.
-*/
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-static int jrnlBufferSize(Pager *pPager){
-  assert( !MEMDB );
-  if( !pPager->tempFile ){
-    int dc;                           /* Device characteristics */
-    int nSector;                      /* Sector size */
-    int szPage;                       /* Page size */
-
-    assert( isOpen(pPager->fd) );
-    dc = sqlite3OsDeviceCharacteristics(pPager->fd);
-    nSector = pPager->sectorSize;
-    szPage = pPager->pageSize;
-
-    assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
-    assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
-    if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){
-      return 0;
-    }
-  }
-
-  return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
-}
-#endif
-
-/*
-** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
-** on the cache using a hash function.  This is used for testing
-** and debugging only.
-*/
-#ifdef SQLITE_CHECK_PAGES
-/*
-** Return a 32-bit hash of the page data for pPage.
-*/
-static u32 pager_datahash(int nByte, unsigned char *pData){
-  u32 hash = 0;
-  int i;
-  for(i=0; i<nByte; i++){
-    hash = (hash*1039) + pData[i];
-  }
-  return hash;
-}
-static u32 pager_pagehash(PgHdr *pPage){
-  return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);
-}
-static void pager_set_pagehash(PgHdr *pPage){
-  pPage->pageHash = pager_pagehash(pPage);
-}
-
-/*
-** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
-** is defined, and NDEBUG is not defined, an assert() statement checks
-** that the page is either dirty or still matches the calculated page-hash.
-*/
-#define CHECK_PAGE(x) checkPage(x)
-static void checkPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  assert( pPager->eState!=PAGER_ERROR );
-  assert( (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
-}
-
-#else
-#define pager_datahash(X,Y)  0
-#define pager_pagehash(X)  0
-#define pager_set_pagehash(X)
-#define CHECK_PAGE(x)
-#endif  /* SQLITE_CHECK_PAGES */
-
-/*
-** When this is called the journal file for pager pPager must be open.
-** This function attempts to read a master journal file name from the 
-** end of the file and, if successful, copies it into memory supplied 
-** by the caller. See comments above writeMasterJournal() for the format
-** used to store a master journal file name at the end of a journal file.
-**
-** zMaster must point to a buffer of at least nMaster bytes allocated by
-** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
-** enough space to write the master journal name). If the master journal
-** name in the journal is longer than nMaster bytes (including a
-** nul-terminator), then this is handled as if no master journal name
-** were present in the journal.
-**
-** If a master journal file name is present at the end of the journal
-** file, then it is copied into the buffer pointed to by zMaster. A
-** nul-terminator byte is appended to the buffer following the master
-** journal file name.
-**
-** If it is determined that no master journal file name is present 
-** zMaster[0] is set to 0 and SQLITE_OK returned.
-**
-** If an error occurs while reading from the journal file, an SQLite
-** error code is returned.
-*/
-static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){
-  int rc;                    /* Return code */
-  u32 len;                   /* Length in bytes of master journal name */
-  i64 szJ;                   /* Total size in bytes of journal file pJrnl */
-  u32 cksum;                 /* MJ checksum value read from journal */
-  u32 u;                     /* Unsigned loop counter */
-  unsigned char aMagic[8];   /* A buffer to hold the magic header */
-  zMaster[0] = '\0';
-
-  if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ))
-   || szJ<16
-   || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
-   || len>=nMaster 
-   || len==0 
-   || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
-   || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
-   || memcmp(aMagic, aJournalMagic, 8)
-   || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len))
-  ){
-    return rc;
-  }
-
-  /* See if the checksum matches the master journal name */
-  for(u=0; u<len; u++){
-    cksum -= zMaster[u];
-  }
-  if( cksum ){
-    /* If the checksum doesn't add up, then one or more of the disk sectors
-    ** containing the master journal filename is corrupted. This means
-    ** definitely roll back, so just return SQLITE_OK and report a (nul)
-    ** master-journal filename.
-    */
-    len = 0;
-  }
-  zMaster[len] = '\0';
-   
-  return SQLITE_OK;
-}
-
-/*
-** Return the offset of the sector boundary at or immediately 
-** following the value in pPager->journalOff, assuming a sector 
-** size of pPager->sectorSize bytes.
-**
-** i.e for a sector size of 512:
-**
-**   Pager.journalOff          Return value
-**   ---------------------------------------
-**   0                         0
-**   512                       512
-**   100                       512
-**   2000                      2048
-** 
-*/
-static i64 journalHdrOffset(Pager *pPager){
-  i64 offset = 0;
-  i64 c = pPager->journalOff;
-  if( c ){
-    offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
-  }
-  assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
-  assert( offset>=c );
-  assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
-  return offset;
-}
-
-/*
-** The journal file must be open when this function is called.
-**
-** This function is a no-op if the journal file has not been written to
-** within the current transaction (i.e. if Pager.journalOff==0).
-**
-** If doTruncate is non-zero or the Pager.journalSizeLimit variable is
-** set to 0, then truncate the journal file to zero bytes in size. Otherwise,
-** zero the 28-byte header at the start of the journal file. In either case, 
-** if the pager is not in no-sync mode, sync the journal file immediately 
-** after writing or truncating it.
-**
-** If Pager.journalSizeLimit is set to a positive, non-zero value, and
-** following the truncation or zeroing described above the size of the 
-** journal file in bytes is larger than this value, then truncate the
-** journal file to Pager.journalSizeLimit bytes. The journal file does
-** not need to be synced following this operation.
-**
-** If an IO error occurs, abandon processing and return the IO error code.
-** Otherwise, return SQLITE_OK.
-*/
-static int zeroJournalHdr(Pager *pPager, int doTruncate){
-  int rc = SQLITE_OK;                               /* Return code */
-  assert( isOpen(pPager->jfd) );
-  if( pPager->journalOff ){
-    const i64 iLimit = pPager->journalSizeLimit;    /* Local cache of jsl */
-
-    IOTRACE(("JZEROHDR %p\n", pPager))
-    if( doTruncate || iLimit==0 ){
-      rc = sqlite3OsTruncate(pPager->jfd, 0);
-    }else{
-      static const char zeroHdr[28] = {0};
-      rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
-    }
-    if( rc==SQLITE_OK && !pPager->noSync ){
-      rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->syncFlags);
-    }
-
-    /* At this point the transaction is committed but the write lock 
-    ** is still held on the file. If there is a size limit configured for 
-    ** the persistent journal and the journal file currently consumes more
-    ** space than that limit allows for, truncate it now. There is no need
-    ** to sync the file following this operation.
-    */
-    if( rc==SQLITE_OK && iLimit>0 ){
-      i64 sz;
-      rc = sqlite3OsFileSize(pPager->jfd, &sz);
-      if( rc==SQLITE_OK && sz>iLimit ){
-        rc = sqlite3OsTruncate(pPager->jfd, iLimit);
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** The journal file must be open when this routine is called. A journal
-** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
-** current location.
-**
-** The format for the journal header is as follows:
-** - 8 bytes: Magic identifying journal format.
-** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
-** - 4 bytes: Random number used for page hash.
-** - 4 bytes: Initial database page count.
-** - 4 bytes: Sector size used by the process that wrote this journal.
-** - 4 bytes: Database page size.
-** 
-** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
-*/
-static int writeJournalHdr(Pager *pPager){
-  int rc = SQLITE_OK;                 /* Return code */
-  char *zHeader = pPager->pTmpSpace;  /* Temporary space used to build header */
-  u32 nHeader = (u32)pPager->pageSize;/* Size of buffer pointed to by zHeader */
-  u32 nWrite;                         /* Bytes of header sector written */
-  int ii;                             /* Loop counter */
-
-  assert( isOpen(pPager->jfd) );      /* Journal file must be open. */
-
-  if( nHeader>JOURNAL_HDR_SZ(pPager) ){
-    nHeader = JOURNAL_HDR_SZ(pPager);
-  }
-
-  /* If there are active savepoints and any of them were created 
-  ** since the most recent journal header was written, update the 
-  ** PagerSavepoint.iHdrOffset fields now.
-  */
-  for(ii=0; ii<pPager->nSavepoint; ii++){
-    if( pPager->aSavepoint[ii].iHdrOffset==0 ){
-      pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff;
-    }
-  }
-
-  pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager);
-
-  /* 
-  ** Write the nRec Field - the number of page records that follow this
-  ** journal header. Normally, zero is written to this value at this time.
-  ** After the records are added to the journal (and the journal synced, 
-  ** if in full-sync mode), the zero is overwritten with the true number
-  ** of records (see syncJournal()).
-  **
-  ** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
-  ** reading the journal this value tells SQLite to assume that the
-  ** rest of the journal file contains valid page records. This assumption
-  ** is dangerous, as if a failure occurred whilst writing to the journal
-  ** file it may contain some garbage data. There are two scenarios
-  ** where this risk can be ignored:
-  **
-  **   * When the pager is in no-sync mode. Corruption can follow a
-  **     power failure in this case anyway.
-  **
-  **   * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
-  **     that garbage data is never appended to the journal file.
-  */
-  assert( isOpen(pPager->fd) || pPager->noSync );
-  if( pPager->noSync || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
-   || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND) 
-  ){
-    memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
-    put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
-  }else{
-    memset(zHeader, 0, sizeof(aJournalMagic)+4);
-  }
-
-  /* The random check-hash initializer */ 
-  sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
-  put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
-  /* The initial database size */
-  put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize);
-  /* The assumed sector size for this process */
-  put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
-
-  /* The page size */
-  put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
-
-  /* Initializing the tail of the buffer is not necessary.  Everything
-  ** works find if the following memset() is omitted.  But initializing
-  ** the memory prevents valgrind from complaining, so we are willing to
-  ** take the performance hit.
-  */
-  memset(&zHeader[sizeof(aJournalMagic)+20], 0,
-         nHeader-(sizeof(aJournalMagic)+20));
-
-  /* In theory, it is only necessary to write the 28 bytes that the 
-  ** journal header consumes to the journal file here. Then increment the 
-  ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next 
-  ** record is written to the following sector (leaving a gap in the file
-  ** that will be implicitly filled in by the OS).
-  **
-  ** However it has been discovered that on some systems this pattern can 
-  ** be significantly slower than contiguously writing data to the file,
-  ** even if that means explicitly writing data to the block of 
-  ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what
-  ** is done. 
-  **
-  ** The loop is required here in case the sector-size is larger than the 
-  ** database page size. Since the zHeader buffer is only Pager.pageSize
-  ** bytes in size, more than one call to sqlite3OsWrite() may be required
-  ** to populate the entire journal header sector.
-  */ 
-  for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
-    IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
-    rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
-    assert( pPager->journalHdr <= pPager->journalOff );
-    pPager->journalOff += nHeader;
-  }
-
-  return rc;
-}
-
-/*
-** The journal file must be open when this is called. A journal header file
-** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
-** file. The current location in the journal file is given by
-** pPager->journalOff. See comments above function writeJournalHdr() for
-** a description of the journal header format.
-**
-** If the header is read successfully, *pNRec is set to the number of
-** page records following this header and *pDbSize is set to the size of the
-** database before the transaction began, in pages. Also, pPager->cksumInit
-** is set to the value read from the journal header. SQLITE_OK is returned
-** in this case.
-**
-** If the journal header file appears to be corrupted, SQLITE_DONE is
-** returned and *pNRec and *PDbSize are undefined.  If JOURNAL_HDR_SZ bytes
-** cannot be read from the journal file an error code is returned.
-*/
-static int readJournalHdr(
-  Pager *pPager,               /* Pager object */
-  int isHot,
-  i64 journalSize,             /* Size of the open journal file in bytes */
-  u32 *pNRec,                  /* OUT: Value read from the nRec field */
-  u32 *pDbSize                 /* OUT: Value of original database size field */
-){
-  int rc;                      /* Return code */
-  unsigned char aMagic[8];     /* A buffer to hold the magic header */
-  i64 iHdrOff;                 /* Offset of journal header being read */
-
-  assert( isOpen(pPager->jfd) );      /* Journal file must be open. */
-
-  /* Advance Pager.journalOff to the start of the next sector. If the
-  ** journal file is too small for there to be a header stored at this
-  ** point, return SQLITE_DONE.
-  */
-  pPager->journalOff = journalHdrOffset(pPager);
-  if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
-    return SQLITE_DONE;
-  }
-  iHdrOff = pPager->journalOff;
-
-  /* Read in the first 8 bytes of the journal header. If they do not match
-  ** the  magic string found at the start of each journal header, return
-  ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise,
-  ** proceed.
-  */
-  if( isHot || iHdrOff!=pPager->journalHdr ){
-    rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff);
-    if( rc ){
-      return rc;
-    }
-    if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
-      return SQLITE_DONE;
-    }
-  }
-
-  /* Read the first three 32-bit fields of the journal header: The nRec
-  ** field, the checksum-initializer and the database size at the start
-  ** of the transaction. Return an error code if anything goes wrong.
-  */
-  if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec))
-   || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit))
-   || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize))
-  ){
-    return rc;
-  }
-
-  if( pPager->journalOff==0 ){
-    u32 iPageSize;               /* Page-size field of journal header */
-    u32 iSectorSize;             /* Sector-size field of journal header */
-
-    /* Read the page-size and sector-size journal header fields. */
-    if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
-     || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
-    ){
-      return rc;
-    }
-
-    /* Versions of SQLite prior to 3.5.8 set the page-size field of the
-    ** journal header to zero. In this case, assume that the Pager.pageSize
-    ** variable is already set to the correct page size.
-    */
-    if( iPageSize==0 ){
-      iPageSize = pPager->pageSize;
-    }
-
-    /* Check that the values read from the page-size and sector-size fields
-    ** are within range. To be 'in range', both values need to be a power
-    ** of two greater than or equal to 512 or 32, and not greater than their 
-    ** respective compile time maximum limits.
-    */
-    if( iPageSize<512                  || iSectorSize<32
-     || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE
-     || ((iPageSize-1)&iPageSize)!=0   || ((iSectorSize-1)&iSectorSize)!=0 
-    ){
-      /* If the either the page-size or sector-size in the journal-header is 
-      ** invalid, then the process that wrote the journal-header must have 
-      ** crashed before the header was synced. In this case stop reading 
-      ** the journal file here.
-      */
-      return SQLITE_DONE;
-    }
-
-    /* Update the page-size to match the value read from the journal. 
-    ** Use a testcase() macro to make sure that malloc failure within 
-    ** PagerSetPagesize() is tested.
-    */
-    rc = sqlite3PagerSetPagesize(pPager, &iPageSize, -1);
-    testcase( rc!=SQLITE_OK );
-
-    /* Update the assumed sector-size to match the value used by 
-    ** the process that created this journal. If this journal was
-    ** created by a process other than this one, then this routine
-    ** is being called from within pager_playback(). The local value
-    ** of Pager.sectorSize is restored at the end of that routine.
-    */
-    pPager->sectorSize = iSectorSize;
-  }
-
-  pPager->journalOff += JOURNAL_HDR_SZ(pPager);
-  return rc;
-}
-
-
-/*
-** Write the supplied master journal name into the journal file for pager
-** pPager at the current location. The master journal name must be the last
-** thing written to a journal file. If the pager is in full-sync mode, the
-** journal file descriptor is advanced to the next sector boundary before
-** anything is written. The format is:
-**
-**   + 4 bytes: PAGER_MJ_PGNO.
-**   + N bytes: Master journal filename in utf-8.
-**   + 4 bytes: N (length of master journal name in bytes, no nul-terminator).
-**   + 4 bytes: Master journal name checksum.
-**   + 8 bytes: aJournalMagic[].
-**
-** The master journal page checksum is the sum of the bytes in the master
-** journal name, where each byte is interpreted as a signed 8-bit integer.
-**
-** If zMaster is a NULL pointer (occurs for a single database transaction), 
-** this call is a no-op.
-*/
-static int writeMasterJournal(Pager *pPager, const char *zMaster){
-  int rc;                          /* Return code */
-  int nMaster;                     /* Length of string zMaster */
-  i64 iHdrOff;                     /* Offset of header in journal file */
-  i64 jrnlSize;                    /* Size of journal file on disk */
-  u32 cksum = 0;                   /* Checksum of string zMaster */
-
-  assert( pPager->setMaster==0 );
-  assert( !pagerUseWal(pPager) );
-
-  if( !zMaster 
-   || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
-   || !isOpen(pPager->jfd)
-  ){
-    return SQLITE_OK;
-  }
-  pPager->setMaster = 1;
-  assert( pPager->journalHdr <= pPager->journalOff );
-
-  /* Calculate the length in bytes and the checksum of zMaster */
-  for(nMaster=0; zMaster[nMaster]; nMaster++){
-    cksum += zMaster[nMaster];
-  }
-
-  /* If in full-sync mode, advance to the next disk sector before writing
-  ** the master journal name. This is in case the previous page written to
-  ** the journal has already been synced.
-  */
-  if( pPager->fullSync ){
-    pPager->journalOff = journalHdrOffset(pPager);
-  }
-  iHdrOff = pPager->journalOff;
-
-  /* Write the master journal data to the end of the journal file. If
-  ** an error occurs, return the error code to the caller.
-  */
-  if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_MJ_PGNO(pPager))))
-   || (0 != (rc = sqlite3OsWrite(pPager->jfd, zMaster, nMaster, iHdrOff+4)))
-   || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster, nMaster)))
-   || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster+4, cksum)))
-   || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8,
-                                 iHdrOff+4+nMaster+8)))
-  ){
-    return rc;
-  }
-  pPager->journalOff += (nMaster+20);
-
-  /* If the pager is in peristent-journal mode, then the physical 
-  ** journal-file may extend past the end of the master-journal name
-  ** and 8 bytes of magic data just written to the file. This is 
-  ** dangerous because the code to rollback a hot-journal file
-  ** will not be able to find the master-journal name to determine 
-  ** whether or not the journal is hot. 
-  **
-  ** Easiest thing to do in this scenario is to truncate the journal 
-  ** file to the required size.
-  */ 
-  if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))
-   && jrnlSize>pPager->journalOff
-  ){
-    rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff);
-  }
-  return rc;
-}
-
-/*
-** Discard the entire contents of the in-memory page-cache.
-*/
-static void pager_reset(Pager *pPager){
-  pPager->iDataVersion++;
-  sqlite3BackupRestart(pPager->pBackup);
-  sqlite3PcacheClear(pPager->pPCache);
-}
-
-/*
-** Return the pPager->iDataVersion value
-*/
-u32 sqlite3PagerDataVersion(Pager *pPager){
-  assert( pPager->eState>PAGER_OPEN );
-  return pPager->iDataVersion;
-}
-
-/*
-** Free all structures in the Pager.aSavepoint[] array and set both
-** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
-** if it is open and the pager is not in exclusive mode.
-*/
-static void releaseAllSavepoints(Pager *pPager){
-  int ii;               /* Iterator for looping through Pager.aSavepoint */
-  for(ii=0; ii<pPager->nSavepoint; ii++){
-    sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
-  }
-  if( !pPager->exclusiveMode || sqlite3IsMemJournal(pPager->sjfd) ){
-    sqlite3OsClose(pPager->sjfd);
-  }
-  sqlite3_free(pPager->aSavepoint);
-  pPager->aSavepoint = 0;
-  pPager->nSavepoint = 0;
-  pPager->nSubRec = 0;
-}
-
-/*
-** Set the bit number pgno in the PagerSavepoint.pInSavepoint 
-** bitvecs of all open savepoints. Return SQLITE_OK if successful
-** or SQLITE_NOMEM if a malloc failure occurs.
-*/
-static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){
-  int ii;                   /* Loop counter */
-  int rc = SQLITE_OK;       /* Result code */
-
-  for(ii=0; ii<pPager->nSavepoint; ii++){
-    PagerSavepoint *p = &pPager->aSavepoint[ii];
-    if( pgno<=p->nOrig ){
-      rc |= sqlite3BitvecSet(p->pInSavepoint, pgno);
-      testcase( rc==SQLITE_NOMEM );
-      assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
-    }
-  }
-  return rc;
-}
-
-/*
-** This function is a no-op if the pager is in exclusive mode and not
-** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN
-** state.
-**
-** If the pager is not in exclusive-access mode, the database file is
-** completely unlocked. If the file is unlocked and the file-system does
-** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is
-** closed (if it is open).
-**
-** If the pager is in ERROR state when this function is called, the 
-** contents of the pager cache are discarded before switching back to 
-** the OPEN state. Regardless of whether the pager is in exclusive-mode
-** or not, any journal file left in the file-system will be treated
-** as a hot-journal and rolled back the next time a read-transaction
-** is opened (by this or by any other connection).
-*/
-static void pager_unlock(Pager *pPager){
-
-  assert( pPager->eState==PAGER_READER 
-       || pPager->eState==PAGER_OPEN 
-       || pPager->eState==PAGER_ERROR 
-  );
-
-  sqlite3BitvecDestroy(pPager->pInJournal);
-  pPager->pInJournal = 0;
-  releaseAllSavepoints(pPager);
-
-  if( pagerUseWal(pPager) ){
-    assert( !isOpen(pPager->jfd) );
-    sqlite3WalEndReadTransaction(pPager->pWal);
-    pPager->eState = PAGER_OPEN;
-  }else if( !pPager->exclusiveMode ){
-    int rc;                       /* Error code returned by pagerUnlockDb() */
-    int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0;
-
-    /* If the operating system support deletion of open files, then
-    ** close the journal file when dropping the database lock.  Otherwise
-    ** another connection with journal_mode=delete might delete the file
-    ** out from under us.
-    */
-    assert( (PAGER_JOURNALMODE_MEMORY   & 5)!=1 );
-    assert( (PAGER_JOURNALMODE_OFF      & 5)!=1 );
-    assert( (PAGER_JOURNALMODE_WAL      & 5)!=1 );
-    assert( (PAGER_JOURNALMODE_DELETE   & 5)!=1 );
-    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
-    assert( (PAGER_JOURNALMODE_PERSIST  & 5)==1 );
-    if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN)
-     || 1!=(pPager->journalMode & 5)
-    ){
-      sqlite3OsClose(pPager->jfd);
-    }
-
-    /* If the pager is in the ERROR state and the call to unlock the database
-    ** file fails, set the current lock to UNKNOWN_LOCK. See the comment
-    ** above the #define for UNKNOWN_LOCK for an explanation of why this
-    ** is necessary.
-    */
-    rc = pagerUnlockDb(pPager, NO_LOCK);
-    if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){
-      pPager->eLock = UNKNOWN_LOCK;
-    }
-
-    /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
-    ** without clearing the error code. This is intentional - the error
-    ** code is cleared and the cache reset in the block below.
-    */
-    assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
-    pPager->changeCountDone = 0;
-    pPager->eState = PAGER_OPEN;
-  }
-
-  /* If Pager.errCode is set, the contents of the pager cache cannot be
-  ** trusted. Now that there are no outstanding references to the pager,
-  ** it can safely move back to PAGER_OPEN state. This happens in both
-  ** normal and exclusive-locking mode.
-  */
-  if( pPager->errCode ){
-    assert( !MEMDB );
-    pager_reset(pPager);
-    pPager->changeCountDone = pPager->tempFile;
-    pPager->eState = PAGER_OPEN;
-    pPager->errCode = SQLITE_OK;
-    if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
-  }
-
-  pPager->journalOff = 0;
-  pPager->journalHdr = 0;
-  pPager->setMaster = 0;
-}
-
-/*
-** This function is called whenever an IOERR or FULL error that requires
-** the pager to transition into the ERROR state may ahve occurred.
-** The first argument is a pointer to the pager structure, the second 
-** the error-code about to be returned by a pager API function. The 
-** value returned is a copy of the second argument to this function. 
-**
-** If the second argument is SQLITE_FULL, SQLITE_IOERR or one of the
-** IOERR sub-codes, the pager enters the ERROR state and the error code
-** is stored in Pager.errCode. While the pager remains in the ERROR state,
-** all major API calls on the Pager will immediately return Pager.errCode.
-**
-** The ERROR state indicates that the contents of the pager-cache 
-** cannot be trusted. This state can be cleared by completely discarding 
-** the contents of the pager-cache. If a transaction was active when
-** the persistent error occurred, then the rollback journal may need
-** to be replayed to restore the contents of the database file (as if
-** it were a hot-journal).
-*/
-static int pager_error(Pager *pPager, int rc){
-  int rc2 = rc & 0xff;
-  assert( rc==SQLITE_OK || !MEMDB );
-  assert(
-       pPager->errCode==SQLITE_FULL ||
-       pPager->errCode==SQLITE_OK ||
-       (pPager->errCode & 0xff)==SQLITE_IOERR
-  );
-  if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){
-    pPager->errCode = rc;
-    pPager->eState = PAGER_ERROR;
-  }
-  return rc;
-}
-
-static int pager_truncate(Pager *pPager, Pgno nPage);
-
-/*
-** This routine ends a transaction. A transaction is usually ended by 
-** either a COMMIT or a ROLLBACK operation. This routine may be called 
-** after rollback of a hot-journal, or if an error occurs while opening
-** the journal file or writing the very first journal-header of a
-** database transaction.
-** 
-** This routine is never called in PAGER_ERROR state. If it is called
-** in PAGER_NONE or PAGER_SHARED state and the lock held is less
-** exclusive than a RESERVED lock, it is a no-op.
-**
-** Otherwise, any active savepoints are released.
-**
-** If the journal file is open, then it is "finalized". Once a journal 
-** file has been finalized it is not possible to use it to roll back a 
-** transaction. Nor will it be considered to be a hot-journal by this
-** or any other database connection. Exactly how a journal is finalized
-** depends on whether or not the pager is running in exclusive mode and
-** the current journal-mode (Pager.journalMode value), as follows:
-**
-**   journalMode==MEMORY
-**     Journal file descriptor is simply closed. This destroys an 
-**     in-memory journal.
-**
-**   journalMode==TRUNCATE
-**     Journal file is truncated to zero bytes in size.
-**
-**   journalMode==PERSIST
-**     The first 28 bytes of the journal file are zeroed. This invalidates
-**     the first journal header in the file, and hence the entire journal
-**     file. An invalid journal file cannot be rolled back.
-**
-**   journalMode==DELETE
-**     The journal file is closed and deleted using sqlite3OsDelete().
-**
-**     If the pager is running in exclusive mode, this method of finalizing
-**     the journal file is never used. Instead, if the journalMode is
-**     DELETE and the pager is in exclusive mode, the method described under
-**     journalMode==PERSIST is used instead.
-**
-** After the journal is finalized, the pager moves to PAGER_READER state.
-** If running in non-exclusive rollback mode, the lock on the file is 
-** downgraded to a SHARED_LOCK.
-**
-** SQLITE_OK is returned if no error occurs. If an error occurs during
-** any of the IO operations to finalize the journal file or unlock the
-** database then the IO error code is returned to the user. If the 
-** operation to finalize the journal file fails, then the code still
-** tries to unlock the database file if not in exclusive mode. If the
-** unlock operation fails as well, then the first error code related
-** to the first error encountered (the journal finalization one) is
-** returned.
-*/
-static int pager_end_transaction(Pager *pPager, int hasMaster, int bCommit){
-  int rc = SQLITE_OK;      /* Error code from journal finalization operation */
-  int rc2 = SQLITE_OK;     /* Error code from db file unlock operation */
-
-  /* Do nothing if the pager does not have an open write transaction
-  ** or at least a RESERVED lock. This function may be called when there
-  ** is no write-transaction active but a RESERVED or greater lock is
-  ** held under two circumstances:
-  **
-  **   1. After a successful hot-journal rollback, it is called with
-  **      eState==PAGER_NONE and eLock==EXCLUSIVE_LOCK.
-  **
-  **   2. If a connection with locking_mode=exclusive holding an EXCLUSIVE 
-  **      lock switches back to locking_mode=normal and then executes a
-  **      read-transaction, this function is called with eState==PAGER_READER 
-  **      and eLock==EXCLUSIVE_LOCK when the read-transaction is closed.
-  */
-  assert( assert_pager_state(pPager) );
-  assert( pPager->eState!=PAGER_ERROR );
-  if( pPager->eState<PAGER_WRITER_LOCKED && pPager->eLock<RESERVED_LOCK ){
-    return SQLITE_OK;
-  }
-
-  releaseAllSavepoints(pPager);
-  assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
-  if( isOpen(pPager->jfd) ){
-    assert( !pagerUseWal(pPager) );
-
-    /* Finalize the journal file. */
-    if( sqlite3IsMemJournal(pPager->jfd) ){
-      assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY );
-      sqlite3OsClose(pPager->jfd);
-    }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){
-      if( pPager->journalOff==0 ){
-        rc = SQLITE_OK;
-      }else{
-        rc = sqlite3OsTruncate(pPager->jfd, 0);
-        if( rc==SQLITE_OK && pPager->fullSync ){
-          /* Make sure the new file size is written into the inode right away.
-          ** Otherwise the journal might resurrect following a power loss and
-          ** cause the last transaction to roll back.  See
-          ** https://bugzilla.mozilla.org/show_bug.cgi?id=1072773
-          */
-          rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
-        }
-      }
-      pPager->journalOff = 0;
-    }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
-      || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
-    ){
-      rc = zeroJournalHdr(pPager, hasMaster);
-      pPager->journalOff = 0;
-    }else{
-      /* This branch may be executed with Pager.journalMode==MEMORY if
-      ** a hot-journal was just rolled back. In this case the journal
-      ** file should be closed and deleted. If this connection writes to
-      ** the database file, it will do so using an in-memory journal. 
-      */
-      int bDelete = (!pPager->tempFile && sqlite3JournalExists(pPager->jfd));
-      assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE 
-           || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
-           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
-      );
-      sqlite3OsClose(pPager->jfd);
-      if( bDelete ){
-        rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
-      }
-    }
-  }
-
-#ifdef SQLITE_CHECK_PAGES
-  sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
-  if( pPager->dbSize==0 && sqlite3PcacheRefCount(pPager->pPCache)>0 ){
-    PgHdr *p = sqlite3PagerLookup(pPager, 1);
-    if( p ){
-      p->pageHash = 0;
-      sqlite3PagerUnrefNotNull(p);
-    }
-  }
-#endif
-
-  sqlite3BitvecDestroy(pPager->pInJournal);
-  pPager->pInJournal = 0;
-  pPager->nRec = 0;
-  sqlite3PcacheCleanAll(pPager->pPCache);
-  sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
-
-  if( pagerUseWal(pPager) ){
-    /* Drop the WAL write-lock, if any. Also, if the connection was in 
-    ** locking_mode=exclusive mode but is no longer, drop the EXCLUSIVE 
-    ** lock held on the database file.
-    */
-    rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
-    assert( rc2==SQLITE_OK );
-  }else if( rc==SQLITE_OK && bCommit && pPager->dbFileSize>pPager->dbSize ){
-    /* This branch is taken when committing a transaction in rollback-journal
-    ** mode if the database file on disk is larger than the database image.
-    ** At this point the journal has been finalized and the transaction 
-    ** successfully committed, but the EXCLUSIVE lock is still held on the
-    ** file. So it is safe to truncate the database file to its minimum
-    ** required size.  */
-    assert( pPager->eLock==EXCLUSIVE_LOCK );
-    rc = pager_truncate(pPager, pPager->dbSize);
-  }
-
-  if( rc==SQLITE_OK && bCommit && isOpen(pPager->fd) ){
-    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0);
-    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
-  }
-
-  if( !pPager->exclusiveMode 
-   && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
-  ){
-    rc2 = pagerUnlockDb(pPager, SHARED_LOCK);
-    pPager->changeCountDone = 0;
-  }
-  pPager->eState = PAGER_READER;
-  pPager->setMaster = 0;
-
-  return (rc==SQLITE_OK?rc2:rc);
-}
-
-/*
-** Execute a rollback if a transaction is active and unlock the 
-** database file. 
-**
-** If the pager has already entered the ERROR state, do not attempt 
-** the rollback at this time. Instead, pager_unlock() is called. The
-** call to pager_unlock() will discard all in-memory pages, unlock
-** the database file and move the pager back to OPEN state. If this 
-** means that there is a hot-journal left in the file-system, the next 
-** connection to obtain a shared lock on the pager (which may be this one) 
-** will roll it back.
-**
-** If the pager has not already entered the ERROR state, but an IO or
-** malloc error occurs during a rollback, then this will itself cause 
-** the pager to enter the ERROR state. Which will be cleared by the
-** call to pager_unlock(), as described above.
-*/
-static void pagerUnlockAndRollback(Pager *pPager){
-  if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){
-    assert( assert_pager_state(pPager) );
-    if( pPager->eState>=PAGER_WRITER_LOCKED ){
-      sqlite3BeginBenignMalloc();
-      sqlite3PagerRollback(pPager);
-      sqlite3EndBenignMalloc();
-    }else if( !pPager->exclusiveMode ){
-      assert( pPager->eState==PAGER_READER );
-      pager_end_transaction(pPager, 0, 0);
-    }
-  }
-  pager_unlock(pPager);
-}
-
-/*
-** Parameter aData must point to a buffer of pPager->pageSize bytes
-** of data. Compute and return a checksum based ont the contents of the 
-** page of data and the current value of pPager->cksumInit.
-**
-** This is not a real checksum. It is really just the sum of the 
-** random initial value (pPager->cksumInit) and every 200th byte
-** of the page data, starting with byte offset (pPager->pageSize%200).
-** Each byte is interpreted as an 8-bit unsigned integer.
-**
-** Changing the formula used to compute this checksum results in an
-** incompatible journal file format.
-**
-** If journal corruption occurs due to a power failure, the most likely 
-** scenario is that one end or the other of the record will be changed. 
-** It is much less likely that the two ends of the journal record will be
-** correct and the middle be corrupt.  Thus, this "checksum" scheme,
-** though fast and simple, catches the mostly likely kind of corruption.
-*/
-static u32 pager_cksum(Pager *pPager, const u8 *aData){
-  u32 cksum = pPager->cksumInit;         /* Checksum value to return */
-  int i = pPager->pageSize-200;          /* Loop counter */
-  while( i>0 ){
-    cksum += aData[i];
-    i -= 200;
-  }
-  return cksum;
-}
-
-/*
-** Report the current page size and number of reserved bytes back
-** to the codec.
-*/
-#ifdef SQLITE_HAS_CODEC
-static void pagerReportSize(Pager *pPager){
-  if( pPager->xCodecSizeChng ){
-    pPager->xCodecSizeChng(pPager->pCodec, pPager->pageSize,
-                           (int)pPager->nReserve);
-  }
-}
-#else
-# define pagerReportSize(X)     /* No-op if we do not support a codec */
-#endif
-
-#ifdef SQLITE_HAS_CODEC
-/*
-** Make sure the number of reserved bits is the same in the destination
-** pager as it is in the source.  This comes up when a VACUUM changes the
-** number of reserved bits to the "optimal" amount.
-*/
-void sqlite3PagerAlignReserve(Pager *pDest, Pager *pSrc){
-  if( pDest->nReserve!=pSrc->nReserve ){
-    pDest->nReserve = pSrc->nReserve;
-    pagerReportSize(pDest);
-  }
-}
-#endif
-
-/*
-** Read a single page from either the journal file (if isMainJrnl==1) or
-** from the sub-journal (if isMainJrnl==0) and playback that page.
-** The page begins at offset *pOffset into the file. The *pOffset
-** value is increased to the start of the next page in the journal.
-**
-** The main rollback journal uses checksums - the statement journal does 
-** not.
-**
-** If the page number of the page record read from the (sub-)journal file
-** is greater than the current value of Pager.dbSize, then playback is
-** skipped and SQLITE_OK is returned.
-**
-** If pDone is not NULL, then it is a record of pages that have already
-** been played back.  If the page at *pOffset has already been played back
-** (if the corresponding pDone bit is set) then skip the playback.
-** Make sure the pDone bit corresponding to the *pOffset page is set
-** prior to returning.
-**
-** If the page record is successfully read from the (sub-)journal file
-** and played back, then SQLITE_OK is returned. If an IO error occurs
-** while reading the record from the (sub-)journal file or while writing
-** to the database file, then the IO error code is returned. If data
-** is successfully read from the (sub-)journal file but appears to be
-** corrupted, SQLITE_DONE is returned. Data is considered corrupted in
-** two circumstances:
-** 
-**   * If the record page-number is illegal (0 or PAGER_MJ_PGNO), or
-**   * If the record is being rolled back from the main journal file
-**     and the checksum field does not match the record content.
-**
-** Neither of these two scenarios are possible during a savepoint rollback.
-**
-** If this is a savepoint rollback, then memory may have to be dynamically
-** allocated by this function. If this is the case and an allocation fails,
-** SQLITE_NOMEM is returned.
-*/
-static int pager_playback_one_page(
-  Pager *pPager,                /* The pager being played back */
-  i64 *pOffset,                 /* Offset of record to playback */
-  Bitvec *pDone,                /* Bitvec of pages already played back */
-  int isMainJrnl,               /* 1 -> main journal. 0 -> sub-journal. */
-  int isSavepnt                 /* True for a savepoint rollback */
-){
-  int rc;
-  PgHdr *pPg;                   /* An existing page in the cache */
-  Pgno pgno;                    /* The page number of a page in journal */
-  u32 cksum;                    /* Checksum used for sanity checking */
-  char *aData;                  /* Temporary storage for the page */
-  sqlite3_file *jfd;            /* The file descriptor for the journal file */
-  int isSynced;                 /* True if journal page is synced */
-
-  assert( (isMainJrnl&~1)==0 );      /* isMainJrnl is 0 or 1 */
-  assert( (isSavepnt&~1)==0 );       /* isSavepnt is 0 or 1 */
-  assert( isMainJrnl || pDone );     /* pDone always used on sub-journals */
-  assert( isSavepnt || pDone==0 );   /* pDone never used on non-savepoint */
-
-  aData = pPager->pTmpSpace;
-  assert( aData );         /* Temp storage must have already been allocated */
-  assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) );
-
-  /* Either the state is greater than PAGER_WRITER_CACHEMOD (a transaction 
-  ** or savepoint rollback done at the request of the caller) or this is
-  ** a hot-journal rollback. If it is a hot-journal rollback, the pager
-  ** is in state OPEN and holds an EXCLUSIVE lock. Hot-journal rollback
-  ** only reads from the main journal, not the sub-journal.
-  */
-  assert( pPager->eState>=PAGER_WRITER_CACHEMOD
-       || (pPager->eState==PAGER_OPEN && pPager->eLock==EXCLUSIVE_LOCK)
-  );
-  assert( pPager->eState>=PAGER_WRITER_CACHEMOD || isMainJrnl );
-
-  /* Read the page number and page data from the journal or sub-journal
-  ** file. Return an error code to the caller if an IO error occurs.
-  */
-  jfd = isMainJrnl ? pPager->jfd : pPager->sjfd;
-  rc = read32bits(jfd, *pOffset, &pgno);
-  if( rc!=SQLITE_OK ) return rc;
-  rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4);
-  if( rc!=SQLITE_OK ) return rc;
-  *pOffset += pPager->pageSize + 4 + isMainJrnl*4;
-
-  /* Sanity checking on the page.  This is more important that I originally
-  ** thought.  If a power failure occurs while the journal is being written,
-  ** it could cause invalid data to be written into the journal.  We need to
-  ** detect this invalid data (with high probability) and ignore it.
-  */
-  if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
-    assert( !isSavepnt );
-    return SQLITE_DONE;
-  }
-  if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){
-    return SQLITE_OK;
-  }
-  if( isMainJrnl ){
-    rc = read32bits(jfd, (*pOffset)-4, &cksum);
-    if( rc ) return rc;
-    if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){
-      return SQLITE_DONE;
-    }
-  }
-
-  /* If this page has already been played back before during the current
-  ** rollback, then don't bother to play it back again.
-  */
-  if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
-    return rc;
-  }
-
-  /* When playing back page 1, restore the nReserve setting
-  */
-  if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){
-    pPager->nReserve = ((u8*)aData)[20];
-    pagerReportSize(pPager);
-  }
-
-  /* If the pager is in CACHEMOD state, then there must be a copy of this
-  ** page in the pager cache. In this case just update the pager cache,
-  ** not the database file. The page is left marked dirty in this case.
-  **
-  ** An exception to the above rule: If the database is in no-sync mode
-  ** and a page is moved during an incremental vacuum then the page may
-  ** not be in the pager cache. Later: if a malloc() or IO error occurs
-  ** during a Movepage() call, then the page may not be in the cache
-  ** either. So the condition described in the above paragraph is not
-  ** assert()able.
-  **
-  ** If in WRITER_DBMOD, WRITER_FINISHED or OPEN state, then we update the
-  ** pager cache if it exists and the main file. The page is then marked 
-  ** not dirty. Since this code is only executed in PAGER_OPEN state for
-  ** a hot-journal rollback, it is guaranteed that the page-cache is empty
-  ** if the pager is in OPEN state.
-  **
-  ** Ticket #1171:  The statement journal might contain page content that is
-  ** different from the page content at the start of the transaction.
-  ** This occurs when a page is changed prior to the start of a statement
-  ** then changed again within the statement.  When rolling back such a
-  ** statement we must not write to the original database unless we know
-  ** for certain that original page contents are synced into the main rollback
-  ** journal.  Otherwise, a power loss might leave modified data in the
-  ** database file without an entry in the rollback journal that can
-  ** restore the database to its original form.  Two conditions must be
-  ** met before writing to the database files. (1) the database must be
-  ** locked.  (2) we know that the original page content is fully synced
-  ** in the main journal either because the page is not in cache or else
-  ** the page is marked as needSync==0.
-  **
-  ** 2008-04-14:  When attempting to vacuum a corrupt database file, it
-  ** is possible to fail a statement on a database that does not yet exist.
-  ** Do not attempt to write if database file has never been opened.
-  */
-  if( pagerUseWal(pPager) ){
-    pPg = 0;
-  }else{
-    pPg = sqlite3PagerLookup(pPager, pgno);
-  }
-  assert( pPg || !MEMDB );
-  assert( pPager->eState!=PAGER_OPEN || pPg==0 );
-  PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
-           PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData),
-           (isMainJrnl?"main-journal":"sub-journal")
-  ));
-  if( isMainJrnl ){
-    isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
-  }else{
-    isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
-  }
-  if( isOpen(pPager->fd)
-   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
-   && isSynced
-  ){
-    i64 ofst = (pgno-1)*(i64)pPager->pageSize;
-    testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
-    assert( !pagerUseWal(pPager) );
-    rc = sqlite3OsWrite(pPager->fd, (u8 *)aData, pPager->pageSize, ofst);
-    if( pgno>pPager->dbFileSize ){
-      pPager->dbFileSize = pgno;
-    }
-    if( pPager->pBackup ){
-      CODEC1(pPager, aData, pgno, 3, rc=SQLITE_NOMEM);
-      sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData);
-      CODEC2(pPager, aData, pgno, 7, rc=SQLITE_NOMEM, aData);
-    }
-  }else if( !isMainJrnl && pPg==0 ){
-    /* If this is a rollback of a savepoint and data was not written to
-    ** the database and the page is not in-memory, there is a potential
-    ** problem. When the page is next fetched by the b-tree layer, it 
-    ** will be read from the database file, which may or may not be 
-    ** current. 
-    **
-    ** There are a couple of different ways this can happen. All are quite
-    ** obscure. When running in synchronous mode, this can only happen 
-    ** if the page is on the free-list at the start of the transaction, then
-    ** populated, then moved using sqlite3PagerMovepage().
-    **
-    ** The solution is to add an in-memory page to the cache containing
-    ** the data just read from the sub-journal. Mark the page as dirty 
-    ** and if the pager requires a journal-sync, then mark the page as 
-    ** requiring a journal-sync before it is written.
-    */
-    assert( isSavepnt );
-    assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)==0 );
-    pPager->doNotSpill |= SPILLFLAG_ROLLBACK;
-    rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1);
-    assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 );
-    pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK;
-    if( rc!=SQLITE_OK ) return rc;
-    pPg->flags &= ~PGHDR_NEED_READ;
-    sqlite3PcacheMakeDirty(pPg);
-  }
-  if( pPg ){
-    /* No page should ever be explicitly rolled back that is in use, except
-    ** for page 1 which is held in use in order to keep the lock on the
-    ** database active. However such a page may be rolled back as a result
-    ** of an internal error resulting in an automatic call to
-    ** sqlite3PagerRollback().
-    */
-    void *pData;
-    pData = pPg->pData;
-    memcpy(pData, (u8*)aData, pPager->pageSize);
-    pPager->xReiniter(pPg);
-    if( isMainJrnl && (!isSavepnt || *pOffset<=pPager->journalHdr) ){
-      /* If the contents of this page were just restored from the main 
-      ** journal file, then its content must be as they were when the 
-      ** transaction was first opened. In this case we can mark the page
-      ** as clean, since there will be no need to write it out to the
-      ** database.
-      **
-      ** There is one exception to this rule. If the page is being rolled
-      ** back as part of a savepoint (or statement) rollback from an 
-      ** unsynced portion of the main journal file, then it is not safe
-      ** to mark the page as clean. This is because marking the page as
-      ** clean will clear the PGHDR_NEED_SYNC flag. Since the page is
-      ** already in the journal file (recorded in Pager.pInJournal) and
-      ** the PGHDR_NEED_SYNC flag is cleared, if the page is written to
-      ** again within this transaction, it will be marked as dirty but
-      ** the PGHDR_NEED_SYNC flag will not be set. It could then potentially
-      ** be written out into the database file before its journal file
-      ** segment is synced. If a crash occurs during or following this,
-      ** database corruption may ensue.
-      */
-      assert( !pagerUseWal(pPager) );
-      sqlite3PcacheMakeClean(pPg);
-    }
-    pager_set_pagehash(pPg);
-
-    /* If this was page 1, then restore the value of Pager.dbFileVers.
-    ** Do this before any decoding. */
-    if( pgno==1 ){
-      memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
-    }
-
-    /* Decode the page just read from disk */
-    CODEC1(pPager, pData, pPg->pgno, 3, rc=SQLITE_NOMEM);
-    sqlite3PcacheRelease(pPg);
-  }
-  return rc;
-}
-
-/*
-** Parameter zMaster is the name of a master journal file. A single journal
-** file that referred to the master journal file has just been rolled back.
-** This routine checks if it is possible to delete the master journal file,
-** and does so if it is.
-**
-** Argument zMaster may point to Pager.pTmpSpace. So that buffer is not 
-** available for use within this function.
-**
-** When a master journal file is created, it is populated with the names 
-** of all of its child journals, one after another, formatted as utf-8 
-** encoded text. The end of each child journal file is marked with a 
-** nul-terminator byte (0x00). i.e. the entire contents of a master journal
-** file for a transaction involving two databases might be:
-**
-**   "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00"
-**
-** A master journal file may only be deleted once all of its child 
-** journals have been rolled back.
-**
-** This function reads the contents of the master-journal file into 
-** memory and loops through each of the child journal names. For
-** each child journal, it checks if:
-**
-**   * if the child journal exists, and if so
-**   * if the child journal contains a reference to master journal 
-**     file zMaster
-**
-** If a child journal can be found that matches both of the criteria
-** above, this function returns without doing anything. Otherwise, if
-** no such child journal can be found, file zMaster is deleted from
-** the file-system using sqlite3OsDelete().
-**
-** If an IO error within this function, an error code is returned. This
-** function allocates memory by calling sqlite3Malloc(). If an allocation
-** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors 
-** occur, SQLITE_OK is returned.
-**
-** TODO: This function allocates a single block of memory to load
-** the entire contents of the master journal file. This could be
-** a couple of kilobytes or so - potentially larger than the page 
-** size.
-*/
-static int pager_delmaster(Pager *pPager, const char *zMaster){
-  sqlite3_vfs *pVfs = pPager->pVfs;
-  int rc;                   /* Return code */
-  sqlite3_file *pMaster;    /* Malloc'd master-journal file descriptor */
-  sqlite3_file *pJournal;   /* Malloc'd child-journal file descriptor */
-  char *zMasterJournal = 0; /* Contents of master journal file */
-  i64 nMasterJournal;       /* Size of master journal file */
-  char *zJournal;           /* Pointer to one journal within MJ file */
-  char *zMasterPtr;         /* Space to hold MJ filename from a journal file */
-  int nMasterPtr;           /* Amount of space allocated to zMasterPtr[] */
-
-  /* Allocate space for both the pJournal and pMaster file descriptors.
-  ** If successful, open the master journal file for reading.
-  */
-  pMaster = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2);
-  pJournal = (sqlite3_file *)(((u8 *)pMaster) + pVfs->szOsFile);
-  if( !pMaster ){
-    rc = SQLITE_NOMEM;
-  }else{
-    const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MASTER_JOURNAL);
-    rc = sqlite3OsOpen(pVfs, zMaster, pMaster, flags, 0);
-  }
-  if( rc!=SQLITE_OK ) goto delmaster_out;
-
-  /* Load the entire master journal file into space obtained from
-  ** sqlite3_malloc() and pointed to by zMasterJournal.   Also obtain
-  ** sufficient space (in zMasterPtr) to hold the names of master
-  ** journal files extracted from regular rollback-journals.
-  */
-  rc = sqlite3OsFileSize(pMaster, &nMasterJournal);
-  if( rc!=SQLITE_OK ) goto delmaster_out;
-  nMasterPtr = pVfs->mxPathname+1;
-  zMasterJournal = sqlite3Malloc(nMasterJournal + nMasterPtr + 1);
-  if( !zMasterJournal ){
-    rc = SQLITE_NOMEM;
-    goto delmaster_out;
-  }
-  zMasterPtr = &zMasterJournal[nMasterJournal+1];
-  rc = sqlite3OsRead(pMaster, zMasterJournal, (int)nMasterJournal, 0);
-  if( rc!=SQLITE_OK ) goto delmaster_out;
-  zMasterJournal[nMasterJournal] = 0;
-
-  zJournal = zMasterJournal;
-  while( (zJournal-zMasterJournal)<nMasterJournal ){
-    int exists;
-    rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists);
-    if( rc!=SQLITE_OK ){
-      goto delmaster_out;
-    }
-    if( exists ){
-      /* One of the journals pointed to by the master journal exists.
-      ** Open it and check if it points at the master journal. If
-      ** so, return without deleting the master journal file.
-      */
-      int c;
-      int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL);
-      rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0);
-      if( rc!=SQLITE_OK ){
-        goto delmaster_out;
-      }
-
-      rc = readMasterJournal(pJournal, zMasterPtr, nMasterPtr);
-      sqlite3OsClose(pJournal);
-      if( rc!=SQLITE_OK ){
-        goto delmaster_out;
-      }
-
-      c = zMasterPtr[0]!=0 && strcmp(zMasterPtr, zMaster)==0;
-      if( c ){
-        /* We have a match. Do not delete the master journal file. */
-        goto delmaster_out;
-      }
-    }
-    zJournal += (sqlite3Strlen30(zJournal)+1);
-  }
- 
-  sqlite3OsClose(pMaster);
-  rc = sqlite3OsDelete(pVfs, zMaster, 0);
-
-delmaster_out:
-  sqlite3_free(zMasterJournal);
-  if( pMaster ){
-    sqlite3OsClose(pMaster);
-    assert( !isOpen(pJournal) );
-    sqlite3_free(pMaster);
-  }
-  return rc;
-}
-
-
-/*
-** This function is used to change the actual size of the database 
-** file in the file-system. This only happens when committing a transaction,
-** or rolling back a transaction (including rolling back a hot-journal).
-**
-** If the main database file is not open, or the pager is not in either
-** DBMOD or OPEN state, this function is a no-op. Otherwise, the size 
-** of the file is changed to nPage pages (nPage*pPager->pageSize bytes). 
-** If the file on disk is currently larger than nPage pages, then use the VFS
-** xTruncate() method to truncate it.
-**
-** Or, it might be the case that the file on disk is smaller than 
-** nPage pages. Some operating system implementations can get confused if 
-** you try to truncate a file to some size that is larger than it 
-** currently is, so detect this case and write a single zero byte to 
-** the end of the new file instead.
-**
-** If successful, return SQLITE_OK. If an IO error occurs while modifying
-** the database file, return the error code to the caller.
-*/
-static int pager_truncate(Pager *pPager, Pgno nPage){
-  int rc = SQLITE_OK;
-  assert( pPager->eState!=PAGER_ERROR );
-  assert( pPager->eState!=PAGER_READER );
-  
-  if( isOpen(pPager->fd) 
-   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) 
-  ){
-    i64 currentSize, newSize;
-    int szPage = pPager->pageSize;
-    assert( pPager->eLock==EXCLUSIVE_LOCK );
-    /* TODO: Is it safe to use Pager.dbFileSize here? */
-    rc = sqlite3OsFileSize(pPager->fd, &currentSize);
-    newSize = szPage*(i64)nPage;
-    if( rc==SQLITE_OK && currentSize!=newSize ){
-      if( currentSize>newSize ){
-        rc = sqlite3OsTruncate(pPager->fd, newSize);
-      }else if( (currentSize+szPage)<=newSize ){
-        char *pTmp = pPager->pTmpSpace;
-        memset(pTmp, 0, szPage);
-        testcase( (newSize-szPage) == currentSize );
-        testcase( (newSize-szPage) >  currentSize );
-        rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, newSize-szPage);
-      }
-      if( rc==SQLITE_OK ){
-        pPager->dbFileSize = nPage;
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Return a sanitized version of the sector-size of OS file pFile. The
-** return value is guaranteed to lie between 32 and MAX_SECTOR_SIZE.
-*/
-int sqlite3SectorSize(sqlite3_file *pFile){
-  int iRet = sqlite3OsSectorSize(pFile);
-  if( iRet<32 ){
-    iRet = 512;
-  }else if( iRet>MAX_SECTOR_SIZE ){
-    assert( MAX_SECTOR_SIZE>=512 );
-    iRet = MAX_SECTOR_SIZE;
-  }
-  return iRet;
-}
-
-/*
-** Set the value of the Pager.sectorSize variable for the given
-** pager based on the value returned by the xSectorSize method
-** of the open database file. The sector size will be used 
-** to determine the size and alignment of journal header and 
-** master journal pointers within created journal files.
-**
-** For temporary files the effective sector size is always 512 bytes.
-**
-** Otherwise, for non-temporary files, the effective sector size is
-** the value returned by the xSectorSize() method rounded up to 32 if
-** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it
-** is greater than MAX_SECTOR_SIZE.
-**
-** If the file has the SQLITE_IOCAP_POWERSAFE_OVERWRITE property, then set
-** the effective sector size to its minimum value (512).  The purpose of
-** pPager->sectorSize is to define the "blast radius" of bytes that
-** might change if a crash occurs while writing to a single byte in
-** that range.  But with POWERSAFE_OVERWRITE, the blast radius is zero
-** (that is what POWERSAFE_OVERWRITE means), so we minimize the sector
-** size.  For backwards compatibility of the rollback journal file format,
-** we cannot reduce the effective sector size below 512.
-*/
-static void setSectorSize(Pager *pPager){
-  assert( isOpen(pPager->fd) || pPager->tempFile );
-
-  if( pPager->tempFile
-   || (sqlite3OsDeviceCharacteristics(pPager->fd) & 
-              SQLITE_IOCAP_POWERSAFE_OVERWRITE)!=0
-  ){
-    /* Sector size doesn't matter for temporary files. Also, the file
-    ** may not have been opened yet, in which case the OsSectorSize()
-    ** call will segfault. */
-    pPager->sectorSize = 512;
-  }else{
-    pPager->sectorSize = sqlite3SectorSize(pPager->fd);
-  }
-}
-
-/*
-** Playback the journal and thus restore the database file to
-** the state it was in before we started making changes.  
-**
-** The journal file format is as follows: 
-**
-**  (1)  8 byte prefix.  A copy of aJournalMagic[].
-**  (2)  4 byte big-endian integer which is the number of valid page records
-**       in the journal.  If this value is 0xffffffff, then compute the
-**       number of page records from the journal size.
-**  (3)  4 byte big-endian integer which is the initial value for the 
-**       sanity checksum.
-**  (4)  4 byte integer which is the number of pages to truncate the
-**       database to during a rollback.
-**  (5)  4 byte big-endian integer which is the sector size.  The header
-**       is this many bytes in size.
-**  (6)  4 byte big-endian integer which is the page size.
-**  (7)  zero padding out to the next sector size.
-**  (8)  Zero or more pages instances, each as follows:
-**        +  4 byte page number.
-**        +  pPager->pageSize bytes of data.
-**        +  4 byte checksum
-**
-** When we speak of the journal header, we mean the first 7 items above.
-** Each entry in the journal is an instance of the 8th item.
-**
-** Call the value from the second bullet "nRec".  nRec is the number of
-** valid page entries in the journal.  In most cases, you can compute the
-** value of nRec from the size of the journal file.  But if a power
-** failure occurred while the journal was being written, it could be the
-** case that the size of the journal file had already been increased but
-** the extra entries had not yet made it safely to disk.  In such a case,
-** the value of nRec computed from the file size would be too large.  For
-** that reason, we always use the nRec value in the header.
-**
-** If the nRec value is 0xffffffff it means that nRec should be computed
-** from the file size.  This value is used when the user selects the
-** no-sync option for the journal.  A power failure could lead to corruption
-** in this case.  But for things like temporary table (which will be
-** deleted when the power is restored) we don't care.  
-**
-** If the file opened as the journal file is not a well-formed
-** journal file then all pages up to the first corrupted page are rolled
-** back (or no pages if the journal header is corrupted). The journal file
-** is then deleted and SQLITE_OK returned, just as if no corruption had
-** been encountered.
-**
-** If an I/O or malloc() error occurs, the journal-file is not deleted
-** and an error code is returned.
-**
-** The isHot parameter indicates that we are trying to rollback a journal
-** that might be a hot journal.  Or, it could be that the journal is 
-** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE.
-** If the journal really is hot, reset the pager cache prior rolling
-** back any content.  If the journal is merely persistent, no reset is
-** needed.
-*/
-static int pager_playback(Pager *pPager, int isHot){
-  sqlite3_vfs *pVfs = pPager->pVfs;
-  i64 szJ;                 /* Size of the journal file in bytes */
-  u32 nRec;                /* Number of Records in the journal */
-  u32 u;                   /* Unsigned loop counter */
-  Pgno mxPg = 0;           /* Size of the original file in pages */
-  int rc;                  /* Result code of a subroutine */
-  int res = 1;             /* Value returned by sqlite3OsAccess() */
-  char *zMaster = 0;       /* Name of master journal file if any */
-  int needPagerReset;      /* True to reset page prior to first page rollback */
-  int nPlayback = 0;       /* Total number of pages restored from journal */
-
-  /* Figure out how many records are in the journal.  Abort early if
-  ** the journal is empty.
-  */
-  assert( isOpen(pPager->jfd) );
-  rc = sqlite3OsFileSize(pPager->jfd, &szJ);
-  if( rc!=SQLITE_OK ){
-    goto end_playback;
-  }
-
-  /* Read the master journal name from the journal, if it is present.
-  ** If a master journal file name is specified, but the file is not
-  ** present on disk, then the journal is not hot and does not need to be
-  ** played back.
-  **
-  ** TODO: Technically the following is an error because it assumes that
-  ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that
-  ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c,
-  **  mxPathname is 512, which is the same as the minimum allowable value
-  ** for pageSize.
-  */
-  zMaster = pPager->pTmpSpace;
-  rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
-  if( rc==SQLITE_OK && zMaster[0] ){
-    rc = sqlite3OsAccess(pVfs, zMaster, SQLITE_ACCESS_EXISTS, &res);
-  }
-  zMaster = 0;
-  if( rc!=SQLITE_OK || !res ){
-    goto end_playback;
-  }
-  pPager->journalOff = 0;
-  needPagerReset = isHot;
-
-  /* This loop terminates either when a readJournalHdr() or 
-  ** pager_playback_one_page() call returns SQLITE_DONE or an IO error 
-  ** occurs. 
-  */
-  while( 1 ){
-    /* Read the next journal header from the journal file.  If there are
-    ** not enough bytes left in the journal file for a complete header, or
-    ** it is corrupted, then a process must have failed while writing it.
-    ** This indicates nothing more needs to be rolled back.
-    */
-    rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg);
-    if( rc!=SQLITE_OK ){ 
-      if( rc==SQLITE_DONE ){
-        rc = SQLITE_OK;
-      }
-      goto end_playback;
-    }
-
-    /* If nRec is 0xffffffff, then this journal was created by a process
-    ** working in no-sync mode. This means that the rest of the journal
-    ** file consists of pages, there are no more journal headers. Compute
-    ** the value of nRec based on this assumption.
-    */
-    if( nRec==0xffffffff ){
-      assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
-      nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager));
-    }
-
-    /* If nRec is 0 and this rollback is of a transaction created by this
-    ** process and if this is the final header in the journal, then it means
-    ** that this part of the journal was being filled but has not yet been
-    ** synced to disk.  Compute the number of pages based on the remaining
-    ** size of the file.
-    **
-    ** The third term of the test was added to fix ticket #2565.
-    ** When rolling back a hot journal, nRec==0 always means that the next
-    ** chunk of the journal contains zero pages to be rolled back.  But
-    ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
-    ** the journal, it means that the journal might contain additional
-    ** pages that need to be rolled back and that the number of pages 
-    ** should be computed based on the journal file size.
-    */
-    if( nRec==0 && !isHot &&
-        pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
-      nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
-    }
-
-    /* If this is the first header read from the journal, truncate the
-    ** database file back to its original size.
-    */
-    if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
-      rc = pager_truncate(pPager, mxPg);
-      if( rc!=SQLITE_OK ){
-        goto end_playback;
-      }
-      pPager->dbSize = mxPg;
-    }
-
-    /* Copy original pages out of the journal and back into the 
-    ** database file and/or page cache.
-    */
-    for(u=0; u<nRec; u++){
-      if( needPagerReset ){
-        pager_reset(pPager);
-        needPagerReset = 0;
-      }
-      rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0);
-      if( rc==SQLITE_OK ){
-        nPlayback++;
-      }else{
-        if( rc==SQLITE_DONE ){
-          pPager->journalOff = szJ;
-          break;
-        }else if( rc==SQLITE_IOERR_SHORT_READ ){
-          /* If the journal has been truncated, simply stop reading and
-          ** processing the journal. This might happen if the journal was
-          ** not completely written and synced prior to a crash.  In that
-          ** case, the database should have never been written in the
-          ** first place so it is OK to simply abandon the rollback. */
-          rc = SQLITE_OK;
-          goto end_playback;
-        }else{
-          /* If we are unable to rollback, quit and return the error
-          ** code.  This will cause the pager to enter the error state
-          ** so that no further harm will be done.  Perhaps the next
-          ** process to come along will be able to rollback the database.
-          */
-          goto end_playback;
-        }
-      }
-    }
-  }
-  /*NOTREACHED*/
-  assert( 0 );
-
-end_playback:
-  /* Following a rollback, the database file should be back in its original
-  ** state prior to the start of the transaction, so invoke the
-  ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the
-  ** assertion that the transaction counter was modified.
-  */
-#ifdef SQLITE_DEBUG
-  if( pPager->fd->pMethods ){
-    sqlite3OsFileControlHint(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0);
-  }
-#endif
-
-  /* If this playback is happening automatically as a result of an IO or 
-  ** malloc error that occurred after the change-counter was updated but 
-  ** before the transaction was committed, then the change-counter 
-  ** modification may just have been reverted. If this happens in exclusive 
-  ** mode, then subsequent transactions performed by the connection will not
-  ** update the change-counter at all. This may lead to cache inconsistency
-  ** problems for other processes at some point in the future. So, just
-  ** in case this has happened, clear the changeCountDone flag now.
-  */
-  pPager->changeCountDone = pPager->tempFile;
-
-  if( rc==SQLITE_OK ){
-    zMaster = pPager->pTmpSpace;
-    rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
-    testcase( rc!=SQLITE_OK );
-  }
-  if( rc==SQLITE_OK
-   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
-  ){
-    rc = sqlite3PagerSync(pPager, 0);
-  }
-  if( rc==SQLITE_OK ){
-    rc = pager_end_transaction(pPager, zMaster[0]!='\0', 0);
-    testcase( rc!=SQLITE_OK );
-  }
-  if( rc==SQLITE_OK && zMaster[0] && res ){
-    /* If there was a master journal and this routine will return success,
-    ** see if it is possible to delete the master journal.
-    */
-    rc = pager_delmaster(pPager, zMaster);
-    testcase( rc!=SQLITE_OK );
-  }
-  if( isHot && nPlayback ){
-    sqlite3_log(SQLITE_NOTICE_RECOVER_ROLLBACK, "recovered %d pages from %s",
-                nPlayback, pPager->zJournal);
-  }
-
-  /* The Pager.sectorSize variable may have been updated while rolling
-  ** back a journal created by a process with a different sector size
-  ** value. Reset it to the correct value for this process.
-  */
-  setSectorSize(pPager);
-  return rc;
-}
-
-
-/*
-** Read the content for page pPg out of the database file and into 
-** pPg->pData. A shared lock or greater must be held on the database
-** file before this function is called.
-**
-** If page 1 is read, then the value of Pager.dbFileVers[] is set to
-** the value read from the database file.
-**
-** If an IO error occurs, then the IO error is returned to the caller.
-** Otherwise, SQLITE_OK is returned.
-*/
-static int readDbPage(PgHdr *pPg, u32 iFrame){
-  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
-  Pgno pgno = pPg->pgno;       /* Page number to read */
-  int rc = SQLITE_OK;          /* Return code */
-  int pgsz = pPager->pageSize; /* Number of bytes to read */
-
-  assert( pPager->eState>=PAGER_READER && !MEMDB );
-  assert( isOpen(pPager->fd) );
-
-#ifndef SQLITE_OMIT_WAL
-  if( iFrame ){
-    /* Try to pull the page from the write-ahead log. */
-    rc = sqlite3WalReadFrame(pPager->pWal, iFrame, pgsz, pPg->pData);
-  }else
-#endif
-  {
-    i64 iOffset = (pgno-1)*(i64)pPager->pageSize;
-    rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset);
-    if( rc==SQLITE_IOERR_SHORT_READ ){
-      rc = SQLITE_OK;
-    }
-  }
-
-  if( pgno==1 ){
-    if( rc ){
-      /* If the read is unsuccessful, set the dbFileVers[] to something
-      ** that will never be a valid file version.  dbFileVers[] is a copy
-      ** of bytes 24..39 of the database.  Bytes 28..31 should always be
-      ** zero or the size of the database in page. Bytes 32..35 and 35..39
-      ** should be page numbers which are never 0xffffffff.  So filling
-      ** pPager->dbFileVers[] with all 0xff bytes should suffice.
-      **
-      ** For an encrypted database, the situation is more complex:  bytes
-      ** 24..39 of the database are white noise.  But the probability of
-      ** white noise equaling 16 bytes of 0xff is vanishingly small so
-      ** we should still be ok.
-      */
-      memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
-    }else{
-      u8 *dbFileVers = &((u8*)pPg->pData)[24];
-      memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
-    }
-  }
-  CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM);
-
-  PAGER_INCR(sqlite3_pager_readdb_count);
-  PAGER_INCR(pPager->nRead);
-  IOTRACE(("PGIN %p %d\n", pPager, pgno));
-  PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
-               PAGERID(pPager), pgno, pager_pagehash(pPg)));
-
-  return rc;
-}
-
-/*
-** Update the value of the change-counter at offsets 24 and 92 in
-** the header and the sqlite version number at offset 96.
-**
-** This is an unconditional update.  See also the pager_incr_changecounter()
-** routine which only updates the change-counter if the update is actually
-** needed, as determined by the pPager->changeCountDone state variable.
-*/
-static void pager_write_changecounter(PgHdr *pPg){
-  u32 change_counter;
-
-  /* Increment the value just read and write it back to byte 24. */
-  change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1;
-  put32bits(((char*)pPg->pData)+24, change_counter);
-
-  /* Also store the SQLite version number in bytes 96..99 and in
-  ** bytes 92..95 store the change counter for which the version number
-  ** is valid. */
-  put32bits(((char*)pPg->pData)+92, change_counter);
-  put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER);
-}
-
-#ifndef SQLITE_OMIT_WAL
-/*
-** This function is invoked once for each page that has already been 
-** written into the log file when a WAL transaction is rolled back.
-** Parameter iPg is the page number of said page. The pCtx argument 
-** is actually a pointer to the Pager structure.
-**
-** If page iPg is present in the cache, and has no outstanding references,
-** it is discarded. Otherwise, if there are one or more outstanding
-** references, the page content is reloaded from the database. If the
-** attempt to reload content from the database is required and fails, 
-** return an SQLite error code. Otherwise, SQLITE_OK.
-*/
-static int pagerUndoCallback(void *pCtx, Pgno iPg){
-  int rc = SQLITE_OK;
-  Pager *pPager = (Pager *)pCtx;
-  PgHdr *pPg;
-
-  assert( pagerUseWal(pPager) );
-  pPg = sqlite3PagerLookup(pPager, iPg);
-  if( pPg ){
-    if( sqlite3PcachePageRefcount(pPg)==1 ){
-      sqlite3PcacheDrop(pPg);
-    }else{
-      u32 iFrame = 0;
-      rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame);
-      if( rc==SQLITE_OK ){
-        rc = readDbPage(pPg, iFrame);
-      }
-      if( rc==SQLITE_OK ){
-        pPager->xReiniter(pPg);
-      }
-      sqlite3PagerUnrefNotNull(pPg);
-    }
-  }
-
-  /* Normally, if a transaction is rolled back, any backup processes are
-  ** updated as data is copied out of the rollback journal and into the
-  ** database. This is not generally possible with a WAL database, as
-  ** rollback involves simply truncating the log file. Therefore, if one
-  ** or more frames have already been written to the log (and therefore 
-  ** also copied into the backup databases) as part of this transaction,
-  ** the backups must be restarted.
-  */
-  sqlite3BackupRestart(pPager->pBackup);
-
-  return rc;
-}
-
-/*
-** This function is called to rollback a transaction on a WAL database.
-*/
-static int pagerRollbackWal(Pager *pPager){
-  int rc;                         /* Return Code */
-  PgHdr *pList;                   /* List of dirty pages to revert */
-
-  /* For all pages in the cache that are currently dirty or have already
-  ** been written (but not committed) to the log file, do one of the 
-  ** following:
-  **
-  **   + Discard the cached page (if refcount==0), or
-  **   + Reload page content from the database (if refcount>0).
-  */
-  pPager->dbSize = pPager->dbOrigSize;
-  rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager);
-  pList = sqlite3PcacheDirtyList(pPager->pPCache);
-  while( pList && rc==SQLITE_OK ){
-    PgHdr *pNext = pList->pDirty;
-    rc = pagerUndoCallback((void *)pPager, pList->pgno);
-    pList = pNext;
-  }
-
-  return rc;
-}
-
-/*
-** This function is a wrapper around sqlite3WalFrames(). As well as logging
-** the contents of the list of pages headed by pList (connected by pDirty),
-** this function notifies any active backup processes that the pages have
-** changed. 
-**
-** The list of pages passed into this routine is always sorted by page number.
-** Hence, if page 1 appears anywhere on the list, it will be the first page.
-*/ 
-static int pagerWalFrames(
-  Pager *pPager,                  /* Pager object */
-  PgHdr *pList,                   /* List of frames to log */
-  Pgno nTruncate,                 /* Database size after this commit */
-  int isCommit                    /* True if this is a commit */
-){
-  int rc;                         /* Return code */
-  int nList;                      /* Number of pages in pList */
-  PgHdr *p;                       /* For looping over pages */
-
-  assert( pPager->pWal );
-  assert( pList );
-#ifdef SQLITE_DEBUG
-  /* Verify that the page list is in accending order */
-  for(p=pList; p && p->pDirty; p=p->pDirty){
-    assert( p->pgno < p->pDirty->pgno );
-  }
-#endif
-
-  assert( pList->pDirty==0 || isCommit );
-  if( isCommit ){
-    /* If a WAL transaction is being committed, there is no point in writing
-    ** any pages with page numbers greater than nTruncate into the WAL file.
-    ** They will never be read by any client. So remove them from the pDirty
-    ** list here. */
-    PgHdr **ppNext = &pList;
-    nList = 0;
-    for(p=pList; (*ppNext = p)!=0; p=p->pDirty){
-      if( p->pgno<=nTruncate ){
-        ppNext = &p->pDirty;
-        nList++;
-      }
-    }
-    assert( pList );
-  }else{
-    nList = 1;
-  }
-  pPager->aStat[PAGER_STAT_WRITE] += nList;
-
-  if( pList->pgno==1 ) pager_write_changecounter(pList);
-  rc = sqlite3WalFrames(pPager->pWal, 
-      pPager->pageSize, pList, nTruncate, isCommit, pPager->walSyncFlags
-  );
-  if( rc==SQLITE_OK && pPager->pBackup ){
-    for(p=pList; p; p=p->pDirty){
-      sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
-    }
-  }
-
-#ifdef SQLITE_CHECK_PAGES
-  pList = sqlite3PcacheDirtyList(pPager->pPCache);
-  for(p=pList; p; p=p->pDirty){
-    pager_set_pagehash(p);
-  }
-#endif
-
-  return rc;
-}
-
-/*
-** Begin a read transaction on the WAL.
-**
-** This routine used to be called "pagerOpenSnapshot()" because it essentially
-** makes a snapshot of the database at the current point in time and preserves
-** that snapshot for use by the reader in spite of concurrently changes by
-** other writers or checkpointers.
-*/
-static int pagerBeginReadTransaction(Pager *pPager){
-  int rc;                         /* Return code */
-  int changed = 0;                /* True if cache must be reset */
-
-  assert( pagerUseWal(pPager) );
-  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
-
-  /* sqlite3WalEndReadTransaction() was not called for the previous
-  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
-  ** are in locking_mode=NORMAL and EndRead() was previously called,
-  ** the duplicate call is harmless.
-  */
-  sqlite3WalEndReadTransaction(pPager->pWal);
-
-  rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
-  if( rc!=SQLITE_OK || changed ){
-    pager_reset(pPager);
-    if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
-  }
-
-  return rc;
-}
-#endif
-
-/*
-** This function is called as part of the transition from PAGER_OPEN
-** to PAGER_READER state to determine the size of the database file
-** in pages (assuming the page size currently stored in Pager.pageSize).
-**
-** If no error occurs, SQLITE_OK is returned and the size of the database
-** in pages is stored in *pnPage. Otherwise, an error code (perhaps
-** SQLITE_IOERR_FSTAT) is returned and *pnPage is left unmodified.
-*/
-static int pagerPagecount(Pager *pPager, Pgno *pnPage){
-  Pgno nPage;                     /* Value to return via *pnPage */
-
-  /* Query the WAL sub-system for the database size. The WalDbsize()
-  ** function returns zero if the WAL is not open (i.e. Pager.pWal==0), or
-  ** if the database size is not available. The database size is not
-  ** available from the WAL sub-system if the log file is empty or
-  ** contains no valid committed transactions.
-  */
-  assert( pPager->eState==PAGER_OPEN );
-  assert( pPager->eLock>=SHARED_LOCK );
-  nPage = sqlite3WalDbsize(pPager->pWal);
-
-  /* If the number of pages in the database is not available from the
-  ** WAL sub-system, determine the page counte based on the size of
-  ** the database file.  If the size of the database file is not an
-  ** integer multiple of the page-size, round up the result.
-  */
-  if( nPage==0 ){
-    i64 n = 0;                    /* Size of db file in bytes */
-    assert( isOpen(pPager->fd) || pPager->tempFile );
-    if( isOpen(pPager->fd) ){
-      int rc = sqlite3OsFileSize(pPager->fd, &n);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-    }
-    nPage = (Pgno)((n+pPager->pageSize-1) / pPager->pageSize);
-  }
-
-  /* If the current number of pages in the file is greater than the
-  ** configured maximum pager number, increase the allowed limit so
-  ** that the file can be read.
-  */
-  if( nPage>pPager->mxPgno ){
-    pPager->mxPgno = (Pgno)nPage;
-  }
-
-  *pnPage = nPage;
-  return SQLITE_OK;
-}
-
-#ifndef SQLITE_OMIT_WAL
-/*
-** Check if the *-wal file that corresponds to the database opened by pPager
-** exists if the database is not empy, or verify that the *-wal file does
-** not exist (by deleting it) if the database file is empty.
-**
-** If the database is not empty and the *-wal file exists, open the pager
-** in WAL mode.  If the database is empty or if no *-wal file exists and
-** if no error occurs, make sure Pager.journalMode is not set to
-** PAGER_JOURNALMODE_WAL.
-**
-** Return SQLITE_OK or an error code.
-**
-** The caller must hold a SHARED lock on the database file to call this
-** function. Because an EXCLUSIVE lock on the db file is required to delete 
-** a WAL on a none-empty database, this ensures there is no race condition 
-** between the xAccess() below and an xDelete() being executed by some 
-** other connection.
-*/
-static int pagerOpenWalIfPresent(Pager *pPager){
-  int rc = SQLITE_OK;
-  assert( pPager->eState==PAGER_OPEN );
-  assert( pPager->eLock>=SHARED_LOCK );
-
-  if( !pPager->tempFile ){
-    int isWal;                    /* True if WAL file exists */
-    Pgno nPage;                   /* Size of the database file */
-
-    rc = pagerPagecount(pPager, &nPage);
-    if( rc ) return rc;
-    if( nPage==0 ){
-      rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
-      if( rc==SQLITE_IOERR_DELETE_NOENT ) rc = SQLITE_OK;
-      isWal = 0;
-    }else{
-      rc = sqlite3OsAccess(
-          pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &isWal
-      );
-    }
-    if( rc==SQLITE_OK ){
-      if( isWal ){
-        testcase( sqlite3PcachePagecount(pPager->pPCache)==0 );
-        rc = sqlite3PagerOpenWal(pPager, 0);
-      }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
-        pPager->journalMode = PAGER_JOURNALMODE_DELETE;
-      }
-    }
-  }
-  return rc;
-}
-#endif
-
-/*
-** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
-** the entire master journal file. The case pSavepoint==NULL occurs when 
-** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction 
-** savepoint.
-**
-** When pSavepoint is not NULL (meaning a non-transaction savepoint is 
-** being rolled back), then the rollback consists of up to three stages,
-** performed in the order specified:
-**
-**   * Pages are played back from the main journal starting at byte
-**     offset PagerSavepoint.iOffset and continuing to 
-**     PagerSavepoint.iHdrOffset, or to the end of the main journal
-**     file if PagerSavepoint.iHdrOffset is zero.
-**
-**   * If PagerSavepoint.iHdrOffset is not zero, then pages are played
-**     back starting from the journal header immediately following 
-**     PagerSavepoint.iHdrOffset to the end of the main journal file.
-**
-**   * Pages are then played back from the sub-journal file, starting
-**     with the PagerSavepoint.iSubRec and continuing to the end of
-**     the journal file.
-**
-** Throughout the rollback process, each time a page is rolled back, the
-** corresponding bit is set in a bitvec structure (variable pDone in the
-** implementation below). This is used to ensure that a page is only
-** rolled back the first time it is encountered in either journal.
-**
-** If pSavepoint is NULL, then pages are only played back from the main
-** journal file. There is no need for a bitvec in this case.
-**
-** In either case, before playback commences the Pager.dbSize variable
-** is reset to the value that it held at the start of the savepoint 
-** (or transaction). No page with a page-number greater than this value
-** is played back. If one is encountered it is simply skipped.
-*/
-static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
-  i64 szJ;                 /* Effective size of the main journal */
-  i64 iHdrOff;             /* End of first segment of main-journal records */
-  int rc = SQLITE_OK;      /* Return code */
-  Bitvec *pDone = 0;       /* Bitvec to ensure pages played back only once */
-
-  assert( pPager->eState!=PAGER_ERROR );
-  assert( pPager->eState>=PAGER_WRITER_LOCKED );
-
-  /* Allocate a bitvec to use to store the set of pages rolled back */
-  if( pSavepoint ){
-    pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
-    if( !pDone ){
-      return SQLITE_NOMEM;
-    }
-  }
-
-  /* Set the database size back to the value it was before the savepoint 
-  ** being reverted was opened.
-  */
-  pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
-  pPager->changeCountDone = pPager->tempFile;
-
-  if( !pSavepoint && pagerUseWal(pPager) ){
-    return pagerRollbackWal(pPager);
-  }
-
-  /* Use pPager->journalOff as the effective size of the main rollback
-  ** journal.  The actual file might be larger than this in
-  ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST.  But anything
-  ** past pPager->journalOff is off-limits to us.
-  */
-  szJ = pPager->journalOff;
-  assert( pagerUseWal(pPager)==0 || szJ==0 );
-
-  /* Begin by rolling back records from the main journal starting at
-  ** PagerSavepoint.iOffset and continuing to the next journal header.
-  ** There might be records in the main journal that have a page number
-  ** greater than the current database size (pPager->dbSize) but those
-  ** will be skipped automatically.  Pages are added to pDone as they
-  ** are played back.
-  */
-  if( pSavepoint && !pagerUseWal(pPager) ){
-    iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
-    pPager->journalOff = pSavepoint->iOffset;
-    while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
-      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
-    }
-    assert( rc!=SQLITE_DONE );
-  }else{
-    pPager->journalOff = 0;
-  }
-
-  /* Continue rolling back records out of the main journal starting at
-  ** the first journal header seen and continuing until the effective end
-  ** of the main journal file.  Continue to skip out-of-range pages and
-  ** continue adding pages rolled back to pDone.
-  */
-  while( rc==SQLITE_OK && pPager->journalOff<szJ ){
-    u32 ii;            /* Loop counter */
-    u32 nJRec = 0;     /* Number of Journal Records */
-    u32 dummy;
-    rc = readJournalHdr(pPager, 0, szJ, &nJRec, &dummy);
-    assert( rc!=SQLITE_DONE );
-
-    /*
-    ** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff"
-    ** test is related to ticket #2565.  See the discussion in the
-    ** pager_playback() function for additional information.
-    */
-    if( nJRec==0 
-     && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff
-    ){
-      nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
-    }
-    for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
-      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
-    }
-    assert( rc!=SQLITE_DONE );
-  }
-  assert( rc!=SQLITE_OK || pPager->journalOff>=szJ );
-
-  /* Finally,  rollback pages from the sub-journal.  Page that were
-  ** previously rolled back out of the main journal (and are hence in pDone)
-  ** will be skipped.  Out-of-range pages are also skipped.
-  */
-  if( pSavepoint ){
-    u32 ii;            /* Loop counter */
-    i64 offset = (i64)pSavepoint->iSubRec*(4+pPager->pageSize);
-
-    if( pagerUseWal(pPager) ){
-      rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData);
-    }
-    for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
-      assert( offset==(i64)ii*(4+pPager->pageSize) );
-      rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1);
-    }
-    assert( rc!=SQLITE_DONE );
-  }
-
-  sqlite3BitvecDestroy(pDone);
-  if( rc==SQLITE_OK ){
-    pPager->journalOff = szJ;
-  }
-
-  return rc;
-}
-
-/*
-** Change the maximum number of in-memory pages that are allowed.
-*/
-void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
-  sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
-}
-
-/*
-** Invoke SQLITE_FCNTL_MMAP_SIZE based on the current value of szMmap.
-*/
-static void pagerFixMaplimit(Pager *pPager){
-#if SQLITE_MAX_MMAP_SIZE>0
-  sqlite3_file *fd = pPager->fd;
-  if( isOpen(fd) && fd->pMethods->iVersion>=3 ){
-    sqlite3_int64 sz;
-    sz = pPager->szMmap;
-    pPager->bUseFetch = (sz>0);
-    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz);
-  }
-#endif
-}
-
-/*
-** Change the maximum size of any memory mapping made of the database file.
-*/
-void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 szMmap){
-  pPager->szMmap = szMmap;
-  pagerFixMaplimit(pPager);
-}
-
-/*
-** Free as much memory as possible from the pager.
-*/
-void sqlite3PagerShrink(Pager *pPager){
-  sqlite3PcacheShrink(pPager->pPCache);
-}
-
-/*
-** Adjust settings of the pager to those specified in the pgFlags parameter.
-**
-** The "level" in pgFlags & PAGER_SYNCHRONOUS_MASK sets the robustness
-** of the database to damage due to OS crashes or power failures by
-** changing the number of syncs()s when writing the journals.
-** There are three levels:
-**
-**    OFF       sqlite3OsSync() is never called.  This is the default
-**              for temporary and transient files.
-**
-**    NORMAL    The journal is synced once before writes begin on the
-**              database.  This is normally adequate protection, but
-**              it is theoretically possible, though very unlikely,
-**              that an inopertune power failure could leave the journal
-**              in a state which would cause damage to the database
-**              when it is rolled back.
-**
-**    FULL      The journal is synced twice before writes begin on the
-**              database (with some additional information - the nRec field
-**              of the journal header - being written in between the two
-**              syncs).  If we assume that writing a
-**              single disk sector is atomic, then this mode provides
-**              assurance that the journal will not be corrupted to the
-**              point of causing damage to the database during rollback.
-**
-** The above is for a rollback-journal mode.  For WAL mode, OFF continues
-** to mean that no syncs ever occur.  NORMAL means that the WAL is synced
-** prior to the start of checkpoint and that the database file is synced
-** at the conclusion of the checkpoint if the entire content of the WAL
-** was written back into the database.  But no sync operations occur for
-** an ordinary commit in NORMAL mode with WAL.  FULL means that the WAL
-** file is synced following each commit operation, in addition to the
-** syncs associated with NORMAL.
-**
-** Do not confuse synchronous=FULL with SQLITE_SYNC_FULL.  The
-** SQLITE_SYNC_FULL macro means to use the MacOSX-style full-fsync
-** using fcntl(F_FULLFSYNC).  SQLITE_SYNC_NORMAL means to do an
-** ordinary fsync() call.  There is no difference between SQLITE_SYNC_FULL
-** and SQLITE_SYNC_NORMAL on platforms other than MacOSX.  But the
-** synchronous=FULL versus synchronous=NORMAL setting determines when
-** the xSync primitive is called and is relevant to all platforms.
-**
-** Numeric values associated with these states are OFF==1, NORMAL=2,
-** and FULL=3.
-*/
-#ifndef SQLITE_OMIT_PAGER_PRAGMAS
-void sqlite3PagerSetFlags(
-  Pager *pPager,        /* The pager to set safety level for */
-  unsigned pgFlags      /* Various flags */
-){
-  unsigned level = pgFlags & PAGER_SYNCHRONOUS_MASK;
-  assert( level>=1 && level<=3 );
-  pPager->noSync =  (level==1 || pPager->tempFile) ?1:0;
-  pPager->fullSync = (level==3 && !pPager->tempFile) ?1:0;
-  if( pPager->noSync ){
-    pPager->syncFlags = 0;
-    pPager->ckptSyncFlags = 0;
-  }else if( pgFlags & PAGER_FULLFSYNC ){
-    pPager->syncFlags = SQLITE_SYNC_FULL;
-    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
-  }else if( pgFlags & PAGER_CKPT_FULLFSYNC ){
-    pPager->syncFlags = SQLITE_SYNC_NORMAL;
-    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
-  }else{
-    pPager->syncFlags = SQLITE_SYNC_NORMAL;
-    pPager->ckptSyncFlags = SQLITE_SYNC_NORMAL;
-  }
-  pPager->walSyncFlags = pPager->syncFlags;
-  if( pPager->fullSync ){
-    pPager->walSyncFlags |= WAL_SYNC_TRANSACTIONS;
-  }
-  if( pgFlags & PAGER_CACHESPILL ){
-    pPager->doNotSpill &= ~SPILLFLAG_OFF;
-  }else{
-    pPager->doNotSpill |= SPILLFLAG_OFF;
-  }
-}
-#endif
-
-/*
-** The following global variable is incremented whenever the library
-** attempts to open a temporary file.  This information is used for
-** testing and analysis only.  
-*/
-#ifdef SQLITE_TEST
-int sqlite3_opentemp_count = 0;
-#endif
-
-/*
-** Open a temporary file.
-**
-** Write the file descriptor into *pFile. Return SQLITE_OK on success 
-** or some other error code if we fail. The OS will automatically 
-** delete the temporary file when it is closed.
-**
-** The flags passed to the VFS layer xOpen() call are those specified
-** by parameter vfsFlags ORed with the following:
-**
-**     SQLITE_OPEN_READWRITE
-**     SQLITE_OPEN_CREATE
-**     SQLITE_OPEN_EXCLUSIVE
-**     SQLITE_OPEN_DELETEONCLOSE
-*/
-static int pagerOpentemp(
-  Pager *pPager,        /* The pager object */
-  sqlite3_file *pFile,  /* Write the file descriptor here */
-  int vfsFlags          /* Flags passed through to the VFS */
-){
-  int rc;               /* Return code */
-
-#ifdef SQLITE_TEST
-  sqlite3_opentemp_count++;  /* Used for testing and analysis only */
-#endif
-
-  vfsFlags |=  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
-            SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
-  rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
-  assert( rc!=SQLITE_OK || isOpen(pFile) );
-  return rc;
-}
-
-/*
-** Set the busy handler function.
-**
-** The pager invokes the busy-handler if sqlite3OsLock() returns 
-** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock,
-** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE 
-** lock. It does *not* invoke the busy handler when upgrading from
-** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE
-** (which occurs during hot-journal rollback). Summary:
-**
-**   Transition                        | Invokes xBusyHandler
-**   --------------------------------------------------------
-**   NO_LOCK       -> SHARED_LOCK      | Yes
-**   SHARED_LOCK   -> RESERVED_LOCK    | No
-**   SHARED_LOCK   -> EXCLUSIVE_LOCK   | No
-**   RESERVED_LOCK -> EXCLUSIVE_LOCK   | Yes
-**
-** If the busy-handler callback returns non-zero, the lock is 
-** retried. If it returns zero, then the SQLITE_BUSY error is
-** returned to the caller of the pager API function.
-*/
-void sqlite3PagerSetBusyhandler(
-  Pager *pPager,                       /* Pager object */
-  int (*xBusyHandler)(void *),         /* Pointer to busy-handler function */
-  void *pBusyHandlerArg                /* Argument to pass to xBusyHandler */
-){
-  pPager->xBusyHandler = xBusyHandler;
-  pPager->pBusyHandlerArg = pBusyHandlerArg;
-
-  if( isOpen(pPager->fd) ){
-    void **ap = (void **)&pPager->xBusyHandler;
-    assert( ((int(*)(void *))(ap[0]))==xBusyHandler );
-    assert( ap[1]==pBusyHandlerArg );
-    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_BUSYHANDLER, (void *)ap);
-  }
-}
-
-/*
-** Change the page size used by the Pager object. The new page size 
-** is passed in *pPageSize.
-**
-** If the pager is in the error state when this function is called, it
-** is a no-op. The value returned is the error state error code (i.e. 
-** one of SQLITE_IOERR, an SQLITE_IOERR_xxx sub-code or SQLITE_FULL).
-**
-** Otherwise, if all of the following are true:
-**
-**   * the new page size (value of *pPageSize) is valid (a power 
-**     of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and
-**
-**   * there are no outstanding page references, and
-**
-**   * the database is either not an in-memory database or it is
-**     an in-memory database that currently consists of zero pages.
-**
-** then the pager object page size is set to *pPageSize.
-**
-** If the page size is changed, then this function uses sqlite3PagerMalloc() 
-** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt 
-** fails, SQLITE_NOMEM is returned and the page size remains unchanged. 
-** In all other cases, SQLITE_OK is returned.
-**
-** If the page size is not changed, either because one of the enumerated
-** conditions above is not true, the pager was in error state when this
-** function was called, or because the memory allocation attempt failed, 
-** then *pPageSize is set to the old, retained page size before returning.
-*/
-int sqlite3PagerSetPagesize(Pager *pPager, u32 *pPageSize, int nReserve){
-  int rc = SQLITE_OK;
-
-  /* It is not possible to do a full assert_pager_state() here, as this
-  ** function may be called from within PagerOpen(), before the state
-  ** of the Pager object is internally consistent.
-  **
-  ** At one point this function returned an error if the pager was in 
-  ** PAGER_ERROR state. But since PAGER_ERROR state guarantees that
-  ** there is at least one outstanding page reference, this function
-  ** is a no-op for that case anyhow.
-  */
-
-  u32 pageSize = *pPageSize;
-  assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
-  if( (pPager->memDb==0 || pPager->dbSize==0)
-   && sqlite3PcacheRefCount(pPager->pPCache)==0 
-   && pageSize && pageSize!=(u32)pPager->pageSize 
-  ){
-    char *pNew = NULL;             /* New temp space */
-    i64 nByte = 0;
-
-    if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){
-      rc = sqlite3OsFileSize(pPager->fd, &nByte);
-    }
-    if( rc==SQLITE_OK ){
-      pNew = (char *)sqlite3PageMalloc(pageSize);
-      if( !pNew ) rc = SQLITE_NOMEM;
-    }
-
-    if( rc==SQLITE_OK ){
-      pager_reset(pPager);
-      rc = sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
-    }
-    if( rc==SQLITE_OK ){
-      sqlite3PageFree(pPager->pTmpSpace);
-      pPager->pTmpSpace = pNew;
-      pPager->dbSize = (Pgno)((nByte+pageSize-1)/pageSize);
-      pPager->pageSize = pageSize;
-    }else{
-      sqlite3PageFree(pNew);
-    }
-  }
-
-  *pPageSize = pPager->pageSize;
-  if( rc==SQLITE_OK ){
-    if( nReserve<0 ) nReserve = pPager->nReserve;
-    assert( nReserve>=0 && nReserve<1000 );
-    pPager->nReserve = (i16)nReserve;
-    pagerReportSize(pPager);
-    pagerFixMaplimit(pPager);
-  }
-  return rc;
-}
-
-/*
-** Return a pointer to the "temporary page" buffer held internally
-** by the pager.  This is a buffer that is big enough to hold the
-** entire content of a database page.  This buffer is used internally
-** during rollback and will be overwritten whenever a rollback
-** occurs.  But other modules are free to use it too, as long as
-** no rollbacks are happening.
-*/
-void *sqlite3PagerTempSpace(Pager *pPager){
-  return pPager->pTmpSpace;
-}
-
-/*
-** Attempt to set the maximum database page count if mxPage is positive. 
-** Make no changes if mxPage is zero or negative.  And never reduce the
-** maximum page count below the current size of the database.
-**
-** Regardless of mxPage, return the current maximum page count.
-*/
-int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
-  if( mxPage>0 ){
-    pPager->mxPgno = mxPage;
-  }
-  assert( pPager->eState!=PAGER_OPEN );      /* Called only by OP_MaxPgcnt */
-  assert( pPager->mxPgno>=pPager->dbSize );  /* OP_MaxPgcnt enforces this */
-  return pPager->mxPgno;
-}
-
-/*
-** The following set of routines are used to disable the simulated
-** I/O error mechanism.  These routines are used to avoid simulated
-** errors in places where we do not care about errors.
-**
-** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
-** and generate no code.
-*/
-#ifdef SQLITE_TEST
-extern int sqlite3_io_error_pending;
-extern int sqlite3_io_error_hit;
-static int saved_cnt;
-void disable_simulated_io_errors(void){
-  saved_cnt = sqlite3_io_error_pending;
-  sqlite3_io_error_pending = -1;
-}
-void enable_simulated_io_errors(void){
-  sqlite3_io_error_pending = saved_cnt;
-}
-#else
-# define disable_simulated_io_errors()
-# define enable_simulated_io_errors()
-#endif
-
-/*
-** Read the first N bytes from the beginning of the file into memory
-** that pDest points to. 
-**
-** If the pager was opened on a transient file (zFilename==""), or
-** opened on a file less than N bytes in size, the output buffer is
-** zeroed and SQLITE_OK returned. The rationale for this is that this 
-** function is used to read database headers, and a new transient or
-** zero sized database has a header than consists entirely of zeroes.
-**
-** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered,
-** the error code is returned to the caller and the contents of the
-** output buffer undefined.
-*/
-int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
-  int rc = SQLITE_OK;
-  memset(pDest, 0, N);
-  assert( isOpen(pPager->fd) || pPager->tempFile );
-
-  /* This routine is only called by btree immediately after creating
-  ** the Pager object.  There has not been an opportunity to transition
-  ** to WAL mode yet.
-  */
-  assert( !pagerUseWal(pPager) );
-
-  if( isOpen(pPager->fd) ){
-    IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
-    rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
-    if( rc==SQLITE_IOERR_SHORT_READ ){
-      rc = SQLITE_OK;
-    }
-  }
-  return rc;
-}
-
-/*
-** This function may only be called when a read-transaction is open on
-** the pager. It returns the total number of pages in the database.
-**
-** However, if the file is between 1 and <page-size> bytes in size, then 
-** this is considered a 1 page file.
-*/
-void sqlite3PagerPagecount(Pager *pPager, int *pnPage){
-  assert( pPager->eState>=PAGER_READER );
-  assert( pPager->eState!=PAGER_WRITER_FINISHED );
-  *pnPage = (int)pPager->dbSize;
-}
-
-
-/*
-** Try to obtain a lock of type locktype on the database file. If
-** a similar or greater lock is already held, this function is a no-op
-** (returning SQLITE_OK immediately).
-**
-** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke 
-** the busy callback if the lock is currently not available. Repeat 
-** until the busy callback returns false or until the attempt to 
-** obtain the lock succeeds.
-**
-** Return SQLITE_OK on success and an error code if we cannot obtain
-** the lock. If the lock is obtained successfully, set the Pager.state 
-** variable to locktype before returning.
-*/
-static int pager_wait_on_lock(Pager *pPager, int locktype){
-  int rc;                              /* Return code */
-
-  /* Check that this is either a no-op (because the requested lock is 
-  ** already held), or one of the transitions that the busy-handler
-  ** may be invoked during, according to the comment above
-  ** sqlite3PagerSetBusyhandler().
-  */
-  assert( (pPager->eLock>=locktype)
-       || (pPager->eLock==NO_LOCK && locktype==SHARED_LOCK)
-       || (pPager->eLock==RESERVED_LOCK && locktype==EXCLUSIVE_LOCK)
-  );
-
-  do {
-    rc = pagerLockDb(pPager, locktype);
-  }while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) );
-  return rc;
-}
-
-/*
-** Function assertTruncateConstraint(pPager) checks that one of the 
-** following is true for all dirty pages currently in the page-cache:
-**
-**   a) The page number is less than or equal to the size of the 
-**      current database image, in pages, OR
-**
-**   b) if the page content were written at this time, it would not
-**      be necessary to write the current content out to the sub-journal
-**      (as determined by function subjRequiresPage()).
-**
-** If the condition asserted by this function were not true, and the
-** dirty page were to be discarded from the cache via the pagerStress()
-** routine, pagerStress() would not write the current page content to
-** the database file. If a savepoint transaction were rolled back after
-** this happened, the correct behavior would be to restore the current
-** content of the page. However, since this content is not present in either
-** the database file or the portion of the rollback journal and 
-** sub-journal rolled back the content could not be restored and the
-** database image would become corrupt. It is therefore fortunate that 
-** this circumstance cannot arise.
-*/
-#if defined(SQLITE_DEBUG)
-static void assertTruncateConstraintCb(PgHdr *pPg){
-  assert( pPg->flags&PGHDR_DIRTY );
-  assert( !subjRequiresPage(pPg) || pPg->pgno<=pPg->pPager->dbSize );
-}
-static void assertTruncateConstraint(Pager *pPager){
-  sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb);
-}
-#else
-# define assertTruncateConstraint(pPager)
-#endif
-
-/*
-** Truncate the in-memory database file image to nPage pages. This 
-** function does not actually modify the database file on disk. It 
-** just sets the internal state of the pager object so that the 
-** truncation will be done when the current transaction is committed.
-**
-** This function is only called right before committing a transaction.
-** Once this function has been called, the transaction must either be
-** rolled back or committed. It is not safe to call this function and
-** then continue writing to the database.
-*/
-void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
-  assert( pPager->dbSize>=nPage );
-  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
-  pPager->dbSize = nPage;
-
-  /* At one point the code here called assertTruncateConstraint() to
-  ** ensure that all pages being truncated away by this operation are,
-  ** if one or more savepoints are open, present in the savepoint 
-  ** journal so that they can be restored if the savepoint is rolled
-  ** back. This is no longer necessary as this function is now only
-  ** called right before committing a transaction. So although the 
-  ** Pager object may still have open savepoints (Pager.nSavepoint!=0), 
-  ** they cannot be rolled back. So the assertTruncateConstraint() call
-  ** is no longer correct. */
-}
-
-
-/*
-** This function is called before attempting a hot-journal rollback. It
-** syncs the journal file to disk, then sets pPager->journalHdr to the
-** size of the journal file so that the pager_playback() routine knows
-** that the entire journal file has been synced.
-**
-** Syncing a hot-journal to disk before attempting to roll it back ensures 
-** that if a power-failure occurs during the rollback, the process that
-** attempts rollback following system recovery sees the same journal
-** content as this process.
-**
-** If everything goes as planned, SQLITE_OK is returned. Otherwise, 
-** an SQLite error code.
-*/
-static int pagerSyncHotJournal(Pager *pPager){
-  int rc = SQLITE_OK;
-  if( !pPager->noSync ){
-    rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL);
-  }
-  if( rc==SQLITE_OK ){
-    rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
-  }
-  return rc;
-}
-
-/*
-** Obtain a reference to a memory mapped page object for page number pgno. 
-** The new object will use the pointer pData, obtained from xFetch().
-** If successful, set *ppPage to point to the new page reference
-** and return SQLITE_OK. Otherwise, return an SQLite error code and set
-** *ppPage to zero.
-**
-** Page references obtained by calling this function should be released
-** by calling pagerReleaseMapPage().
-*/
-static int pagerAcquireMapPage(
-  Pager *pPager,                  /* Pager object */
-  Pgno pgno,                      /* Page number */
-  void *pData,                    /* xFetch()'d data for this page */
-  PgHdr **ppPage                  /* OUT: Acquired page object */
-){
-  PgHdr *p;                       /* Memory mapped page to return */
-  
-  if( pPager->pMmapFreelist ){
-    *ppPage = p = pPager->pMmapFreelist;
-    pPager->pMmapFreelist = p->pDirty;
-    p->pDirty = 0;
-    memset(p->pExtra, 0, pPager->nExtra);
-  }else{
-    *ppPage = p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra);
-    if( p==0 ){
-      sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1) * pPager->pageSize, pData);
-      return SQLITE_NOMEM;
-    }
-    p->pExtra = (void *)&p[1];
-    p->flags = PGHDR_MMAP;
-    p->nRef = 1;
-    p->pPager = pPager;
-  }
-
-  assert( p->pExtra==(void *)&p[1] );
-  assert( p->pPage==0 );
-  assert( p->flags==PGHDR_MMAP );
-  assert( p->pPager==pPager );
-  assert( p->nRef==1 );
-
-  p->pgno = pgno;
-  p->pData = pData;
-  pPager->nMmapOut++;
-
-  return SQLITE_OK;
-}
-
-/*
-** Release a reference to page pPg. pPg must have been returned by an 
-** earlier call to pagerAcquireMapPage().
-*/
-static void pagerReleaseMapPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  pPager->nMmapOut--;
-  pPg->pDirty = pPager->pMmapFreelist;
-  pPager->pMmapFreelist = pPg;
-
-  assert( pPager->fd->pMethods->iVersion>=3 );
-  sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData);
-}
-
-/*
-** Free all PgHdr objects stored in the Pager.pMmapFreelist list.
-*/
-static void pagerFreeMapHdrs(Pager *pPager){
-  PgHdr *p;
-  PgHdr *pNext;
-  for(p=pPager->pMmapFreelist; p; p=pNext){
-    pNext = p->pDirty;
-    sqlite3_free(p);
-  }
-}
-
-
-/*
-** Shutdown the page cache.  Free all memory and close all files.
-**
-** If a transaction was in progress when this routine is called, that
-** transaction is rolled back.  All outstanding pages are invalidated
-** and their memory is freed.  Any attempt to use a page associated
-** with this page cache after this function returns will likely
-** result in a coredump.
-**
-** This function always succeeds. If a transaction is active an attempt
-** is made to roll it back. If an error occurs during the rollback 
-** a hot journal may be left in the filesystem but no error is returned
-** to the caller.
-*/
-int sqlite3PagerClose(Pager *pPager){
-  u8 *pTmp = (u8 *)pPager->pTmpSpace;
-
-  assert( assert_pager_state(pPager) );
-  disable_simulated_io_errors();
-  sqlite3BeginBenignMalloc();
-  pagerFreeMapHdrs(pPager);
-  /* pPager->errCode = 0; */
-  pPager->exclusiveMode = 0;
-#ifndef SQLITE_OMIT_WAL
-  sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags, pPager->pageSize, pTmp);
-  pPager->pWal = 0;
-#endif
-  pager_reset(pPager);
-  if( MEMDB ){
-    pager_unlock(pPager);
-  }else{
-    /* If it is open, sync the journal file before calling UnlockAndRollback.
-    ** If this is not done, then an unsynced portion of the open journal 
-    ** file may be played back into the database. If a power failure occurs 
-    ** while this is happening, the database could become corrupt.
-    **
-    ** If an error occurs while trying to sync the journal, shift the pager
-    ** into the ERROR state. This causes UnlockAndRollback to unlock the
-    ** database and close the journal file without attempting to roll it
-    ** back or finalize it. The next database user will have to do hot-journal
-    ** rollback before accessing the database file.
-    */
-    if( isOpen(pPager->jfd) ){
-      pager_error(pPager, pagerSyncHotJournal(pPager));
-    }
-    pagerUnlockAndRollback(pPager);
-  }
-  sqlite3EndBenignMalloc();
-  enable_simulated_io_errors();
-  PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
-  IOTRACE(("CLOSE %p\n", pPager))
-  sqlite3OsClose(pPager->jfd);
-  sqlite3OsClose(pPager->fd);
-  sqlite3PageFree(pTmp);
-  sqlite3PcacheClose(pPager->pPCache);
-
-#ifdef SQLITE_HAS_CODEC
-  if( pPager->xCodecFree ) pPager->xCodecFree(pPager->pCodec);
-#endif
-
-  assert( !pPager->aSavepoint && !pPager->pInJournal );
-  assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) );
-
-  sqlite3_free(pPager);
-  return SQLITE_OK;
-}
-
-#if !defined(NDEBUG) || defined(SQLITE_TEST)
-/*
-** Return the page number for page pPg.
-*/
-Pgno sqlite3PagerPagenumber(DbPage *pPg){
-  return pPg->pgno;
-}
-#endif
-
-/*
-** Increment the reference count for page pPg.
-*/
-void sqlite3PagerRef(DbPage *pPg){
-  sqlite3PcacheRef(pPg);
-}
-
-/*
-** Sync the journal. In other words, make sure all the pages that have
-** been written to the journal have actually reached the surface of the
-** disk and can be restored in the event of a hot-journal rollback.
-**
-** If the Pager.noSync flag is set, then this function is a no-op.
-** Otherwise, the actions required depend on the journal-mode and the 
-** device characteristics of the file-system, as follows:
-**
-**   * If the journal file is an in-memory journal file, no action need
-**     be taken.
-**
-**   * Otherwise, if the device does not support the SAFE_APPEND property,
-**     then the nRec field of the most recently written journal header
-**     is updated to contain the number of journal records that have
-**     been written following it. If the pager is operating in full-sync
-**     mode, then the journal file is synced before this field is updated.
-**
-**   * If the device does not support the SEQUENTIAL property, then 
-**     journal file is synced.
-**
-** Or, in pseudo-code:
-**
-**   if( NOT <in-memory journal> ){
-**     if( NOT SAFE_APPEND ){
-**       if( <full-sync mode> ) xSync(<journal file>);
-**       <update nRec field>
-**     } 
-**     if( NOT SEQUENTIAL ) xSync(<journal file>);
-**   }
-**
-** If successful, this routine clears the PGHDR_NEED_SYNC flag of every 
-** page currently held in memory before returning SQLITE_OK. If an IO
-** error is encountered, then the IO error code is returned to the caller.
-*/
-static int syncJournal(Pager *pPager, int newHdr){
-  int rc;                         /* Return code */
-
-  assert( pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-  );
-  assert( assert_pager_state(pPager) );
-  assert( !pagerUseWal(pPager) );
-
-  rc = sqlite3PagerExclusiveLock(pPager);
-  if( rc!=SQLITE_OK ) return rc;
-
-  if( !pPager->noSync ){
-    assert( !pPager->tempFile );
-    if( isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
-      const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
-      assert( isOpen(pPager->jfd) );
-
-      if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
-        /* This block deals with an obscure problem. If the last connection
-        ** that wrote to this database was operating in persistent-journal
-        ** mode, then the journal file may at this point actually be larger
-        ** than Pager.journalOff bytes. If the next thing in the journal
-        ** file happens to be a journal-header (written as part of the
-        ** previous connection's transaction), and a crash or power-failure 
-        ** occurs after nRec is updated but before this connection writes 
-        ** anything else to the journal file (or commits/rolls back its 
-        ** transaction), then SQLite may become confused when doing the 
-        ** hot-journal rollback following recovery. It may roll back all
-        ** of this connections data, then proceed to rolling back the old,
-        ** out-of-date data that follows it. Database corruption.
-        **
-        ** To work around this, if the journal file does appear to contain
-        ** a valid header following Pager.journalOff, then write a 0x00
-        ** byte to the start of it to prevent it from being recognized.
-        **
-        ** Variable iNextHdrOffset is set to the offset at which this
-        ** problematic header will occur, if it exists. aMagic is used 
-        ** as a temporary buffer to inspect the first couple of bytes of
-        ** the potential journal header.
-        */
-        i64 iNextHdrOffset;
-        u8 aMagic[8];
-        u8 zHeader[sizeof(aJournalMagic)+4];
-
-        memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
-        put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
-
-        iNextHdrOffset = journalHdrOffset(pPager);
-        rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
-        if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){
-          static const u8 zerobyte = 0;
-          rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset);
-        }
-        if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
-          return rc;
-        }
-
-        /* Write the nRec value into the journal file header. If in
-        ** full-synchronous mode, sync the journal first. This ensures that
-        ** all data has really hit the disk before nRec is updated to mark
-        ** it as a candidate for rollback.
-        **
-        ** This is not required if the persistent media supports the
-        ** SAFE_APPEND property. Because in this case it is not possible 
-        ** for garbage data to be appended to the file, the nRec field
-        ** is populated with 0xFFFFFFFF when the journal header is written
-        ** and never needs to be updated.
-        */
-        if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
-          PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
-          IOTRACE(("JSYNC %p\n", pPager))
-          rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
-          if( rc!=SQLITE_OK ) return rc;
-        }
-        IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr));
-        rc = sqlite3OsWrite(
-            pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr
-        );
-        if( rc!=SQLITE_OK ) return rc;
-      }
-      if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
-        PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
-        IOTRACE(("JSYNC %p\n", pPager))
-        rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags| 
-          (pPager->syncFlags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
-        );
-        if( rc!=SQLITE_OK ) return rc;
-      }
-
-      pPager->journalHdr = pPager->journalOff;
-      if( newHdr && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
-        pPager->nRec = 0;
-        rc = writeJournalHdr(pPager);
-        if( rc!=SQLITE_OK ) return rc;
-      }
-    }else{
-      pPager->journalHdr = pPager->journalOff;
-    }
-  }
-
-  /* Unless the pager is in noSync mode, the journal file was just 
-  ** successfully synced. Either way, clear the PGHDR_NEED_SYNC flag on 
-  ** all pages.
-  */
-  sqlite3PcacheClearSyncFlags(pPager->pPCache);
-  pPager->eState = PAGER_WRITER_DBMOD;
-  assert( assert_pager_state(pPager) );
-  return SQLITE_OK;
-}
-
-/*
-** The argument is the first in a linked list of dirty pages connected
-** by the PgHdr.pDirty pointer. This function writes each one of the
-** in-memory pages in the list to the database file. The argument may
-** be NULL, representing an empty list. In this case this function is
-** a no-op.
-**
-** The pager must hold at least a RESERVED lock when this function
-** is called. Before writing anything to the database file, this lock
-** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained,
-** SQLITE_BUSY is returned and no data is written to the database file.
-** 
-** If the pager is a temp-file pager and the actual file-system file
-** is not yet open, it is created and opened before any data is 
-** written out.
-**
-** Once the lock has been upgraded and, if necessary, the file opened,
-** the pages are written out to the database file in list order. Writing
-** a page is skipped if it meets either of the following criteria:
-**
-**   * The page number is greater than Pager.dbSize, or
-**   * The PGHDR_DONT_WRITE flag is set on the page.
-**
-** If writing out a page causes the database file to grow, Pager.dbFileSize
-** is updated accordingly. If page 1 is written out, then the value cached
-** in Pager.dbFileVers[] is updated to match the new value stored in
-** the database file.
-**
-** If everything is successful, SQLITE_OK is returned. If an IO error 
-** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
-** be obtained, SQLITE_BUSY is returned.
-*/
-static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
-  int rc = SQLITE_OK;                  /* Return code */
-
-  /* This function is only called for rollback pagers in WRITER_DBMOD state. */
-  assert( !pagerUseWal(pPager) );
-  assert( pPager->eState==PAGER_WRITER_DBMOD );
-  assert( pPager->eLock==EXCLUSIVE_LOCK );
-
-  /* If the file is a temp-file has not yet been opened, open it now. It
-  ** is not possible for rc to be other than SQLITE_OK if this branch
-  ** is taken, as pager_wait_on_lock() is a no-op for temp-files.
-  */
-  if( !isOpen(pPager->fd) ){
-    assert( pPager->tempFile && rc==SQLITE_OK );
-    rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
-  }
-
-  /* Before the first write, give the VFS a hint of what the final
-  ** file size will be.
-  */
-  assert( rc!=SQLITE_OK || isOpen(pPager->fd) );
-  if( rc==SQLITE_OK 
-   && pPager->dbHintSize<pPager->dbSize
-   && (pList->pDirty || pList->pgno>pPager->dbHintSize)
-  ){
-    sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
-    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
-    pPager->dbHintSize = pPager->dbSize;
-  }
-
-  while( rc==SQLITE_OK && pList ){
-    Pgno pgno = pList->pgno;
-
-    /* If there are dirty pages in the page cache with page numbers greater
-    ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to
-    ** make the file smaller (presumably by auto-vacuum code). Do not write
-    ** any such pages to the file.
-    **
-    ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
-    ** set (set by sqlite3PagerDontWrite()).
-    */
-    if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
-      i64 offset = (pgno-1)*(i64)pPager->pageSize;   /* Offset to write */
-      char *pData;                                   /* Data to write */    
-
-      assert( (pList->flags&PGHDR_NEED_SYNC)==0 );
-      if( pList->pgno==1 ) pager_write_changecounter(pList);
-
-      /* Encode the database */
-      CODEC2(pPager, pList->pData, pgno, 6, return SQLITE_NOMEM, pData);
-
-      /* Write out the page data. */
-      rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
-
-      /* If page 1 was just written, update Pager.dbFileVers to match
-      ** the value now stored in the database file. If writing this 
-      ** page caused the database file to grow, update dbFileSize. 
-      */
-      if( pgno==1 ){
-        memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
-      }
-      if( pgno>pPager->dbFileSize ){
-        pPager->dbFileSize = pgno;
-      }
-      pPager->aStat[PAGER_STAT_WRITE]++;
-
-      /* Update any backup objects copying the contents of this pager. */
-      sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData);
-
-      PAGERTRACE(("STORE %d page %d hash(%08x)\n",
-                   PAGERID(pPager), pgno, pager_pagehash(pList)));
-      IOTRACE(("PGOUT %p %d\n", pPager, pgno));
-      PAGER_INCR(sqlite3_pager_writedb_count);
-    }else{
-      PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno));
-    }
-    pager_set_pagehash(pList);
-    pList = pList->pDirty;
-  }
-
-  return rc;
-}
-
-/*
-** Ensure that the sub-journal file is open. If it is already open, this 
-** function is a no-op.
-**
-** SQLITE_OK is returned if everything goes according to plan. An 
-** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen() 
-** fails.
-*/
-static int openSubJournal(Pager *pPager){
-  int rc = SQLITE_OK;
-  if( !isOpen(pPager->sjfd) ){
-    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
-      sqlite3MemJournalOpen(pPager->sjfd);
-    }else{
-      rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
-    }
-  }
-  return rc;
-}
-
-/*
-** Append a record of the current state of page pPg to the sub-journal. 
-**
-** If successful, set the bit corresponding to pPg->pgno in the bitvecs
-** for all open savepoints before returning.
-**
-** This function returns SQLITE_OK if everything is successful, an IO
-** error code if the attempt to write to the sub-journal fails, or 
-** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint
-** bitvec.
-*/
-static int subjournalPage(PgHdr *pPg){
-  int rc = SQLITE_OK;
-  Pager *pPager = pPg->pPager;
-  if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
-
-    /* Open the sub-journal, if it has not already been opened */
-    assert( pPager->useJournal );
-    assert( isOpen(pPager->jfd) || pagerUseWal(pPager) );
-    assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 );
-    assert( pagerUseWal(pPager) 
-         || pageInJournal(pPager, pPg) 
-         || pPg->pgno>pPager->dbOrigSize 
-    );
-    rc = openSubJournal(pPager);
-
-    /* If the sub-journal was opened successfully (or was already open),
-    ** write the journal record into the file.  */
-    if( rc==SQLITE_OK ){
-      void *pData = pPg->pData;
-      i64 offset = (i64)pPager->nSubRec*(4+pPager->pageSize);
-      char *pData2;
-  
-      CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
-      PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
-      rc = write32bits(pPager->sjfd, offset, pPg->pgno);
-      if( rc==SQLITE_OK ){
-        rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
-      }
-    }
-  }
-  if( rc==SQLITE_OK ){
-    pPager->nSubRec++;
-    assert( pPager->nSavepoint>0 );
-    rc = addToSavepointBitvecs(pPager, pPg->pgno);
-  }
-  return rc;
-}
-static int subjournalPageIfRequired(PgHdr *pPg){
-  if( subjRequiresPage(pPg) ){
-    return subjournalPage(pPg);
-  }else{
-    return SQLITE_OK;
-  }
-}
-
-/*
-** This function is called by the pcache layer when it has reached some
-** soft memory limit. The first argument is a pointer to a Pager object
-** (cast as a void*). The pager is always 'purgeable' (not an in-memory
-** database). The second argument is a reference to a page that is 
-** currently dirty but has no outstanding references. The page
-** is always associated with the Pager object passed as the first 
-** argument.
-**
-** The job of this function is to make pPg clean by writing its contents
-** out to the database file, if possible. This may involve syncing the
-** journal file. 
-**
-** If successful, sqlite3PcacheMakeClean() is called on the page and
-** SQLITE_OK returned. If an IO error occurs while trying to make the
-** page clean, the IO error code is returned. If the page cannot be
-** made clean for some other reason, but no error occurs, then SQLITE_OK
-** is returned by sqlite3PcacheMakeClean() is not called.
-*/
-static int pagerStress(void *p, PgHdr *pPg){
-  Pager *pPager = (Pager *)p;
-  int rc = SQLITE_OK;
-
-  assert( pPg->pPager==pPager );
-  assert( pPg->flags&PGHDR_DIRTY );
-
-  /* The doNotSpill NOSYNC bit is set during times when doing a sync of
-  ** journal (and adding a new header) is not allowed.  This occurs
-  ** during calls to sqlite3PagerWrite() while trying to journal multiple
-  ** pages belonging to the same sector.
-  **
-  ** The doNotSpill ROLLBACK and OFF bits inhibits all cache spilling
-  ** regardless of whether or not a sync is required.  This is set during
-  ** a rollback or by user request, respectively.
-  **
-  ** Spilling is also prohibited when in an error state since that could
-  ** lead to database corruption.   In the current implementation it 
-  ** is impossible for sqlite3PcacheFetch() to be called with createFlag==3
-  ** while in the error state, hence it is impossible for this routine to
-  ** be called in the error state.  Nevertheless, we include a NEVER()
-  ** test for the error state as a safeguard against future changes.
-  */
-  if( NEVER(pPager->errCode) ) return SQLITE_OK;
-  testcase( pPager->doNotSpill & SPILLFLAG_ROLLBACK );
-  testcase( pPager->doNotSpill & SPILLFLAG_OFF );
-  testcase( pPager->doNotSpill & SPILLFLAG_NOSYNC );
-  if( pPager->doNotSpill
-   && ((pPager->doNotSpill & (SPILLFLAG_ROLLBACK|SPILLFLAG_OFF))!=0
-      || (pPg->flags & PGHDR_NEED_SYNC)!=0)
-  ){
-    return SQLITE_OK;
-  }
-
-  pPg->pDirty = 0;
-  if( pagerUseWal(pPager) ){
-    /* Write a single frame for this page to the log. */
-    rc = subjournalPageIfRequired(pPg); 
-    if( rc==SQLITE_OK ){
-      rc = pagerWalFrames(pPager, pPg, 0, 0);
-    }
-  }else{
-  
-    /* Sync the journal file if required. */
-    if( pPg->flags&PGHDR_NEED_SYNC 
-     || pPager->eState==PAGER_WRITER_CACHEMOD
-    ){
-      rc = syncJournal(pPager, 1);
-    }
-  
-    /* Write the contents of the page out to the database file. */
-    if( rc==SQLITE_OK ){
-      assert( (pPg->flags&PGHDR_NEED_SYNC)==0 );
-      rc = pager_write_pagelist(pPager, pPg);
-    }
-  }
-
-  /* Mark the page as clean. */
-  if( rc==SQLITE_OK ){
-    PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));
-    sqlite3PcacheMakeClean(pPg);
-  }
-
-  return pager_error(pPager, rc); 
-}
-
-
-/*
-** Allocate and initialize a new Pager object and put a pointer to it
-** in *ppPager. The pager should eventually be freed by passing it
-** to sqlite3PagerClose().
-**
-** The zFilename argument is the path to the database file to open.
-** If zFilename is NULL then a randomly-named temporary file is created
-** and used as the file to be cached. Temporary files are be deleted
-** automatically when they are closed. If zFilename is ":memory:" then 
-** all information is held in cache. It is never written to disk. 
-** This can be used to implement an in-memory database.
-**
-** The nExtra parameter specifies the number of bytes of space allocated
-** along with each page reference. This space is available to the user
-** via the sqlite3PagerGetExtra() API.
-**
-** The flags argument is used to specify properties that affect the
-** operation of the pager. It should be passed some bitwise combination
-** of the PAGER_* flags.
-**
-** The vfsFlags parameter is a bitmask to pass to the flags parameter
-** of the xOpen() method of the supplied VFS when opening files. 
-**
-** If the pager object is allocated and the specified file opened 
-** successfully, SQLITE_OK is returned and *ppPager set to point to
-** the new pager object. If an error occurs, *ppPager is set to NULL
-** and error code returned. This function may return SQLITE_NOMEM
-** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or 
-** various SQLITE_IO_XXX errors.
-*/
-int sqlite3PagerOpen(
-  sqlite3_vfs *pVfs,       /* The virtual file system to use */
-  Pager **ppPager,         /* OUT: Return the Pager structure here */
-  const char *zFilename,   /* Name of the database file to open */
-  int nExtra,              /* Extra bytes append to each in-memory page */
-  int flags,               /* flags controlling this file */
-  int vfsFlags,            /* flags passed through to sqlite3_vfs.xOpen() */
-  void (*xReinit)(DbPage*) /* Function to reinitialize pages */
-){
-  u8 *pPtr;
-  Pager *pPager = 0;       /* Pager object to allocate and return */
-  int rc = SQLITE_OK;      /* Return code */
-  int tempFile = 0;        /* True for temp files (incl. in-memory files) */
-  int memDb = 0;           /* True if this is an in-memory file */
-  int readOnly = 0;        /* True if this is a read-only file */
-  int journalFileSize;     /* Bytes to allocate for each journal fd */
-  char *zPathname = 0;     /* Full path to database file */
-  int nPathname = 0;       /* Number of bytes in zPathname */
-  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
-  int pcacheSize = sqlite3PcacheSize();       /* Bytes to allocate for PCache */
-  u32 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE;  /* Default page size */
-  const char *zUri = 0;    /* URI args to copy */
-  int nUri = 0;            /* Number of bytes of URI args at *zUri */
-
-  /* Figure out how much space is required for each journal file-handle
-  ** (there are two of them, the main journal and the sub-journal). This
-  ** is the maximum space required for an in-memory journal file handle 
-  ** and a regular journal file-handle. Note that a "regular journal-handle"
-  ** may be a wrapper capable of caching the first portion of the journal
-  ** file in memory to implement the atomic-write optimization (see 
-  ** source file journal.c).
-  */
-  if( sqlite3JournalSize(pVfs)>sqlite3MemJournalSize() ){
-    journalFileSize = ROUND8(sqlite3JournalSize(pVfs));
-  }else{
-    journalFileSize = ROUND8(sqlite3MemJournalSize());
-  }
-
-  /* Set the output variable to NULL in case an error occurs. */
-  *ppPager = 0;
-
-#ifndef SQLITE_OMIT_MEMORYDB
-  if( flags & PAGER_MEMORY ){
-    memDb = 1;
-    if( zFilename && zFilename[0] ){
-      zPathname = sqlite3DbStrDup(0, zFilename);
-      if( zPathname==0  ) return SQLITE_NOMEM;
-      nPathname = sqlite3Strlen30(zPathname);
-      zFilename = 0;
-    }
-  }
-#endif
-
-  /* Compute and store the full pathname in an allocated buffer pointed
-  ** to by zPathname, length nPathname. Or, if this is a temporary file,
-  ** leave both nPathname and zPathname set to 0.
-  */
-  if( zFilename && zFilename[0] ){
-    const char *z;
-    nPathname = pVfs->mxPathname+1;
-    zPathname = sqlite3DbMallocRaw(0, nPathname*2);
-    if( zPathname==0 ){
-      return SQLITE_NOMEM;
-    }
-    zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */
-    rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
-    nPathname = sqlite3Strlen30(zPathname);
-    z = zUri = &zFilename[sqlite3Strlen30(zFilename)+1];
-    while( *z ){
-      z += sqlite3Strlen30(z)+1;
-      z += sqlite3Strlen30(z)+1;
-    }
-    nUri = (int)(&z[1] - zUri);
-    assert( nUri>=0 );
-    if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
-      /* This branch is taken when the journal path required by
-      ** the database being opened will be more than pVfs->mxPathname
-      ** bytes in length. This means the database cannot be opened,
-      ** as it will not be possible to open the journal file or even
-      ** check for a hot-journal before reading.
-      */
-      rc = SQLITE_CANTOPEN_BKPT;
-    }
-    if( rc!=SQLITE_OK ){
-      sqlite3DbFree(0, zPathname);
-      return rc;
-    }
-  }
-
-  /* Allocate memory for the Pager structure, PCache object, the
-  ** three file descriptors, the database file name and the journal 
-  ** file name. The layout in memory is as follows:
-  **
-  **     Pager object                    (sizeof(Pager) bytes)
-  **     PCache object                   (sqlite3PcacheSize() bytes)
-  **     Database file handle            (pVfs->szOsFile bytes)
-  **     Sub-journal file handle         (journalFileSize bytes)
-  **     Main journal file handle        (journalFileSize bytes)
-  **     Database file name              (nPathname+1 bytes)
-  **     Journal file name               (nPathname+8+1 bytes)
-  */
-  pPtr = (u8 *)sqlite3MallocZero(
-    ROUND8(sizeof(*pPager)) +      /* Pager structure */
-    ROUND8(pcacheSize) +           /* PCache object */
-    ROUND8(pVfs->szOsFile) +       /* The main db file */
-    journalFileSize * 2 +          /* The two journal files */ 
-    nPathname + 1 + nUri +         /* zFilename */
-    nPathname + 8 + 2              /* zJournal */
-#ifndef SQLITE_OMIT_WAL
-    + nPathname + 4 + 2            /* zWal */
-#endif
-  );
-  assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) );
-  if( !pPtr ){
-    sqlite3DbFree(0, zPathname);
-    return SQLITE_NOMEM;
-  }
-  pPager =              (Pager*)(pPtr);
-  pPager->pPCache =    (PCache*)(pPtr += ROUND8(sizeof(*pPager)));
-  pPager->fd =   (sqlite3_file*)(pPtr += ROUND8(pcacheSize));
-  pPager->sjfd = (sqlite3_file*)(pPtr += ROUND8(pVfs->szOsFile));
-  pPager->jfd =  (sqlite3_file*)(pPtr += journalFileSize);
-  pPager->zFilename =    (char*)(pPtr += journalFileSize);
-  assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) );
-
-  /* Fill in the Pager.zFilename and Pager.zJournal buffers, if required. */
-  if( zPathname ){
-    assert( nPathname>0 );
-    pPager->zJournal =   (char*)(pPtr += nPathname + 1 + nUri);
-    memcpy(pPager->zFilename, zPathname, nPathname);
-    if( nUri ) memcpy(&pPager->zFilename[nPathname+1], zUri, nUri);
-    memcpy(pPager->zJournal, zPathname, nPathname);
-    memcpy(&pPager->zJournal[nPathname], "-journal\000", 8+2);
-    sqlite3FileSuffix3(pPager->zFilename, pPager->zJournal);
-#ifndef SQLITE_OMIT_WAL
-    pPager->zWal = &pPager->zJournal[nPathname+8+1];
-    memcpy(pPager->zWal, zPathname, nPathname);
-    memcpy(&pPager->zWal[nPathname], "-wal\000", 4+1);
-    sqlite3FileSuffix3(pPager->zFilename, pPager->zWal);
-#endif
-    sqlite3DbFree(0, zPathname);
-  }
-  pPager->pVfs = pVfs;
-  pPager->vfsFlags = vfsFlags;
-
-  /* Open the pager file.
-  */
-  if( zFilename && zFilename[0] ){
-    int fout = 0;                    /* VFS flags returned by xOpen() */
-    rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
-    assert( !memDb );
-    readOnly = (fout&SQLITE_OPEN_READONLY);
-
-    /* If the file was successfully opened for read/write access,
-    ** choose a default page size in case we have to create the
-    ** database file. The default page size is the maximum of:
-    **
-    **    + SQLITE_DEFAULT_PAGE_SIZE,
-    **    + The value returned by sqlite3OsSectorSize()
-    **    + The largest page size that can be written atomically.
-    */
-    if( rc==SQLITE_OK ){
-      int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
-      if( !readOnly ){
-        setSectorSize(pPager);
-        assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE);
-        if( szPageDflt<pPager->sectorSize ){
-          if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
-            szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
-          }else{
-            szPageDflt = (u32)pPager->sectorSize;
-          }
-        }
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-        {
-          int ii;
-          assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
-          assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
-          assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
-          for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
-            if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){
-              szPageDflt = ii;
-            }
-          }
-        }
-#endif
-      }
-      pPager->noLock = sqlite3_uri_boolean(zFilename, "nolock", 0);
-      if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0
-       || sqlite3_uri_boolean(zFilename, "immutable", 0) ){
-          vfsFlags |= SQLITE_OPEN_READONLY;
-          goto act_like_temp_file;
-      }
-    }
-  }else{
-    /* If a temporary file is requested, it is not opened immediately.
-    ** In this case we accept the default page size and delay actually
-    ** opening the file until the first call to OsWrite().
-    **
-    ** This branch is also run for an in-memory database. An in-memory
-    ** database is the same as a temp-file that is never written out to
-    ** disk and uses an in-memory rollback journal.
-    **
-    ** This branch also runs for files marked as immutable.
-    */ 
-act_like_temp_file:
-    tempFile = 1;
-    pPager->eState = PAGER_READER;     /* Pretend we already have a lock */
-    pPager->eLock = EXCLUSIVE_LOCK;    /* Pretend we are in EXCLUSIVE mode */
-    pPager->noLock = 1;                /* Do no locking */
-    readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
-  }
-
-  /* The following call to PagerSetPagesize() serves to set the value of 
-  ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
-  */
-  if( rc==SQLITE_OK ){
-    assert( pPager->memDb==0 );
-    rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1);
-    testcase( rc!=SQLITE_OK );
-  }
-
-  /* Initialize the PCache object. */
-  if( rc==SQLITE_OK ){
-    assert( nExtra<1000 );
-    nExtra = ROUND8(nExtra);
-    rc = sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
-                       !memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
-  }
-
-  /* If an error occurred above, free the  Pager structure and close the file.
-  */
-  if( rc!=SQLITE_OK ){
-    sqlite3OsClose(pPager->fd);
-    sqlite3PageFree(pPager->pTmpSpace);
-    sqlite3_free(pPager);
-    return rc;
-  }
-
-  PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename));
-  IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
-
-  pPager->useJournal = (u8)useJournal;
-  /* pPager->stmtOpen = 0; */
-  /* pPager->stmtInUse = 0; */
-  /* pPager->nRef = 0; */
-  /* pPager->stmtSize = 0; */
-  /* pPager->stmtJSize = 0; */
-  /* pPager->nPage = 0; */
-  pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
-  /* pPager->state = PAGER_UNLOCK; */
-  /* pPager->errMask = 0; */
-  pPager->tempFile = (u8)tempFile;
-  assert( tempFile==PAGER_LOCKINGMODE_NORMAL 
-          || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
-  assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
-  pPager->exclusiveMode = (u8)tempFile; 
-  pPager->changeCountDone = pPager->tempFile;
-  pPager->memDb = (u8)memDb;
-  pPager->readOnly = (u8)readOnly;
-  assert( useJournal || pPager->tempFile );
-  pPager->noSync = pPager->tempFile;
-  if( pPager->noSync ){
-    assert( pPager->fullSync==0 );
-    assert( pPager->syncFlags==0 );
-    assert( pPager->walSyncFlags==0 );
-    assert( pPager->ckptSyncFlags==0 );
-  }else{
-    pPager->fullSync = 1;
-    pPager->syncFlags = SQLITE_SYNC_NORMAL;
-    pPager->walSyncFlags = SQLITE_SYNC_NORMAL | WAL_SYNC_TRANSACTIONS;
-    pPager->ckptSyncFlags = SQLITE_SYNC_NORMAL;
-  }
-  /* pPager->pFirst = 0; */
-  /* pPager->pFirstSynced = 0; */
-  /* pPager->pLast = 0; */
-  pPager->nExtra = (u16)nExtra;
-  pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
-  assert( isOpen(pPager->fd) || tempFile );
-  setSectorSize(pPager);
-  if( !useJournal ){
-    pPager->journalMode = PAGER_JOURNALMODE_OFF;
-  }else if( memDb ){
-    pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
-  }
-  /* pPager->xBusyHandler = 0; */
-  /* pPager->pBusyHandlerArg = 0; */
-  pPager->xReiniter = xReinit;
-  /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
-  /* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */
-
-  *ppPager = pPager;
-  return SQLITE_OK;
-}
-
-
-/* Verify that the database file has not be deleted or renamed out from
-** under the pager.  Return SQLITE_OK if the database is still were it ought
-** to be on disk.  Return non-zero (SQLITE_READONLY_DBMOVED or some other error
-** code from sqlite3OsAccess()) if the database has gone missing.
-*/
-static int databaseIsUnmoved(Pager *pPager){
-  int bHasMoved = 0;
-  int rc;
-
-  if( pPager->tempFile ) return SQLITE_OK;
-  if( pPager->dbSize==0 ) return SQLITE_OK;
-  assert( pPager->zFilename && pPager->zFilename[0] );
-  rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_HAS_MOVED, &bHasMoved);
-  if( rc==SQLITE_NOTFOUND ){
-    /* If the HAS_MOVED file-control is unimplemented, assume that the file
-    ** has not been moved.  That is the historical behavior of SQLite: prior to
-    ** version 3.8.3, it never checked */
-    rc = SQLITE_OK;
-  }else if( rc==SQLITE_OK && bHasMoved ){
-    rc = SQLITE_READONLY_DBMOVED;
-  }
-  return rc;
-}
-
-
-/*
-** This function is called after transitioning from PAGER_UNLOCK to
-** PAGER_SHARED state. It tests if there is a hot journal present in
-** the file-system for the given pager. A hot journal is one that 
-** needs to be played back. According to this function, a hot-journal
-** file exists if the following criteria are met:
-**
-**   * The journal file exists in the file system, and
-**   * No process holds a RESERVED or greater lock on the database file, and
-**   * The database file itself is greater than 0 bytes in size, and
-**   * The first byte of the journal file exists and is not 0x00.
-**
-** If the current size of the database file is 0 but a journal file
-** exists, that is probably an old journal left over from a prior
-** database with the same name. In this case the journal file is
-** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
-** is returned.
-**
-** This routine does not check if there is a master journal filename
-** at the end of the file. If there is, and that master journal file
-** does not exist, then the journal file is not really hot. In this
-** case this routine will return a false-positive. The pager_playback()
-** routine will discover that the journal file is not really hot and 
-** will not roll it back. 
-**
-** If a hot-journal file is found to exist, *pExists is set to 1 and 
-** SQLITE_OK returned. If no hot-journal file is present, *pExists is
-** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
-** to determine whether or not a hot-journal file exists, the IO error
-** code is returned and the value of *pExists is undefined.
-*/
-static int hasHotJournal(Pager *pPager, int *pExists){
-  sqlite3_vfs * const pVfs = pPager->pVfs;
-  int rc = SQLITE_OK;           /* Return code */
-  int exists = 1;               /* True if a journal file is present */
-  int jrnlOpen = !!isOpen(pPager->jfd);
-
-  assert( pPager->useJournal );
-  assert( isOpen(pPager->fd) );
-  assert( pPager->eState==PAGER_OPEN );
-
-  assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
-    SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
-  ));
-
-  *pExists = 0;
-  if( !jrnlOpen ){
-    rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
-  }
-  if( rc==SQLITE_OK && exists ){
-    int locked = 0;             /* True if some process holds a RESERVED lock */
-
-    /* Race condition here:  Another process might have been holding the
-    ** the RESERVED lock and have a journal open at the sqlite3OsAccess() 
-    ** call above, but then delete the journal and drop the lock before
-    ** we get to the following sqlite3OsCheckReservedLock() call.  If that
-    ** is the case, this routine might think there is a hot journal when
-    ** in fact there is none.  This results in a false-positive which will
-    ** be dealt with by the playback routine.  Ticket #3883.
-    */
-    rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
-    if( rc==SQLITE_OK && !locked ){
-      Pgno nPage;                 /* Number of pages in database file */
-
-      rc = pagerPagecount(pPager, &nPage);
-      if( rc==SQLITE_OK ){
-        /* If the database is zero pages in size, that means that either (1) the
-        ** journal is a remnant from a prior database with the same name where
-        ** the database file but not the journal was deleted, or (2) the initial
-        ** transaction that populates a new database is being rolled back.
-        ** In either case, the journal file can be deleted.  However, take care
-        ** not to delete the journal file if it is already open due to
-        ** journal_mode=PERSIST.
-        */
-        if( nPage==0 && !jrnlOpen ){
-          sqlite3BeginBenignMalloc();
-          if( pagerLockDb(pPager, RESERVED_LOCK)==SQLITE_OK ){
-            sqlite3OsDelete(pVfs, pPager->zJournal, 0);
-            if( !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
-          }
-          sqlite3EndBenignMalloc();
-        }else{
-          /* The journal file exists and no other connection has a reserved
-          ** or greater lock on the database file. Now check that there is
-          ** at least one non-zero bytes at the start of the journal file.
-          ** If there is, then we consider this journal to be hot. If not, 
-          ** it can be ignored.
-          */
-          if( !jrnlOpen ){
-            int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
-            rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
-          }
-          if( rc==SQLITE_OK ){
-            u8 first = 0;
-            rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
-            if( rc==SQLITE_IOERR_SHORT_READ ){
-              rc = SQLITE_OK;
-            }
-            if( !jrnlOpen ){
-              sqlite3OsClose(pPager->jfd);
-            }
-            *pExists = (first!=0);
-          }else if( rc==SQLITE_CANTOPEN ){
-            /* If we cannot open the rollback journal file in order to see if
-            ** it has a zero header, that might be due to an I/O error, or
-            ** it might be due to the race condition described above and in
-            ** ticket #3883.  Either way, assume that the journal is hot.
-            ** This might be a false positive.  But if it is, then the
-            ** automatic journal playback and recovery mechanism will deal
-            ** with it under an EXCLUSIVE lock where we do not need to
-            ** worry so much with race conditions.
-            */
-            *pExists = 1;
-            rc = SQLITE_OK;
-          }
-        }
-      }
-    }
-  }
-
-  return rc;
-}
-
-/*
-** This function is called to obtain a shared lock on the database file.
-** It is illegal to call sqlite3PagerAcquire() until after this function
-** has been successfully called. If a shared-lock is already held when
-** this function is called, it is a no-op.
-**
-** The following operations are also performed by this function.
-**
-**   1) If the pager is currently in PAGER_OPEN state (no lock held
-**      on the database file), then an attempt is made to obtain a
-**      SHARED lock on the database file. Immediately after obtaining
-**      the SHARED lock, the file-system is checked for a hot-journal,
-**      which is played back if present. Following any hot-journal 
-**      rollback, the contents of the cache are validated by checking
-**      the 'change-counter' field of the database file header and
-**      discarded if they are found to be invalid.
-**
-**   2) If the pager is running in exclusive-mode, and there are currently
-**      no outstanding references to any pages, and is in the error state,
-**      then an attempt is made to clear the error state by discarding
-**      the contents of the page cache and rolling back any open journal
-**      file.
-**
-** If everything is successful, SQLITE_OK is returned. If an IO error 
-** occurs while locking the database, checking for a hot-journal file or 
-** rolling back a journal file, the IO error code is returned.
-*/
-int sqlite3PagerSharedLock(Pager *pPager){
-  int rc = SQLITE_OK;                /* Return code */
-
-  /* This routine is only called from b-tree and only when there are no
-  ** outstanding pages. This implies that the pager state should either
-  ** be OPEN or READER. READER is only possible if the pager is or was in 
-  ** exclusive access mode.
-  */
-  assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
-  assert( assert_pager_state(pPager) );
-  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
-  if( NEVER(MEMDB && pPager->errCode) ){ return pPager->errCode; }
-
-  if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){
-    int bHotJournal = 1;          /* True if there exists a hot journal-file */
-
-    assert( !MEMDB );
-
-    rc = pager_wait_on_lock(pPager, SHARED_LOCK);
-    if( rc!=SQLITE_OK ){
-      assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK );
-      goto failed;
-    }
-
-    /* If a journal file exists, and there is no RESERVED lock on the
-    ** database file, then it either needs to be played back or deleted.
-    */
-    if( pPager->eLock<=SHARED_LOCK ){
-      rc = hasHotJournal(pPager, &bHotJournal);
-    }
-    if( rc!=SQLITE_OK ){
-      goto failed;
-    }
-    if( bHotJournal ){
-      if( pPager->readOnly ){
-        rc = SQLITE_READONLY_ROLLBACK;
-        goto failed;
-      }
-
-      /* Get an EXCLUSIVE lock on the database file. At this point it is
-      ** important that a RESERVED lock is not obtained on the way to the
-      ** EXCLUSIVE lock. If it were, another process might open the
-      ** database file, detect the RESERVED lock, and conclude that the
-      ** database is safe to read while this process is still rolling the 
-      ** hot-journal back.
-      ** 
-      ** Because the intermediate RESERVED lock is not requested, any
-      ** other process attempting to access the database file will get to 
-      ** this point in the code and fail to obtain its own EXCLUSIVE lock 
-      ** on the database file.
-      **
-      ** Unless the pager is in locking_mode=exclusive mode, the lock is
-      ** downgraded to SHARED_LOCK before this function returns.
-      */
-      rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
-      if( rc!=SQLITE_OK ){
-        goto failed;
-      }
- 
-      /* If it is not already open and the file exists on disk, open the 
-      ** journal for read/write access. Write access is required because 
-      ** in exclusive-access mode the file descriptor will be kept open 
-      ** and possibly used for a transaction later on. Also, write-access 
-      ** is usually required to finalize the journal in journal_mode=persist 
-      ** mode (and also for journal_mode=truncate on some systems).
-      **
-      ** If the journal does not exist, it usually means that some 
-      ** other connection managed to get in and roll it back before 
-      ** this connection obtained the exclusive lock above. Or, it 
-      ** may mean that the pager was in the error-state when this
-      ** function was called and the journal file does not exist.
-      */
-      if( !isOpen(pPager->jfd) ){
-        sqlite3_vfs * const pVfs = pPager->pVfs;
-        int bExists;              /* True if journal file exists */
-        rc = sqlite3OsAccess(
-            pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &bExists);
-        if( rc==SQLITE_OK && bExists ){
-          int fout = 0;
-          int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
-          assert( !pPager->tempFile );
-          rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
-          assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
-          if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
-            rc = SQLITE_CANTOPEN_BKPT;
-            sqlite3OsClose(pPager->jfd);
-          }
-        }
-      }
- 
-      /* Playback and delete the journal.  Drop the database write
-      ** lock and reacquire the read lock. Purge the cache before
-      ** playing back the hot-journal so that we don't end up with
-      ** an inconsistent cache.  Sync the hot journal before playing
-      ** it back since the process that crashed and left the hot journal
-      ** probably did not sync it and we are required to always sync
-      ** the journal before playing it back.
-      */
-      if( isOpen(pPager->jfd) ){
-        assert( rc==SQLITE_OK );
-        rc = pagerSyncHotJournal(pPager);
-        if( rc==SQLITE_OK ){
-          rc = pager_playback(pPager, 1);
-          pPager->eState = PAGER_OPEN;
-        }
-      }else if( !pPager->exclusiveMode ){
-        pagerUnlockDb(pPager, SHARED_LOCK);
-      }
-
-      if( rc!=SQLITE_OK ){
-        /* This branch is taken if an error occurs while trying to open
-        ** or roll back a hot-journal while holding an EXCLUSIVE lock. The
-        ** pager_unlock() routine will be called before returning to unlock
-        ** the file. If the unlock attempt fails, then Pager.eLock must be
-        ** set to UNKNOWN_LOCK (see the comment above the #define for 
-        ** UNKNOWN_LOCK above for an explanation). 
-        **
-        ** In order to get pager_unlock() to do this, set Pager.eState to
-        ** PAGER_ERROR now. This is not actually counted as a transition
-        ** to ERROR state in the state diagram at the top of this file,
-        ** since we know that the same call to pager_unlock() will very
-        ** shortly transition the pager object to the OPEN state. Calling
-        ** assert_pager_state() would fail now, as it should not be possible
-        ** to be in ERROR state when there are zero outstanding page 
-        ** references.
-        */
-        pager_error(pPager, rc);
-        goto failed;
-      }
-
-      assert( pPager->eState==PAGER_OPEN );
-      assert( (pPager->eLock==SHARED_LOCK)
-           || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK)
-      );
-    }
-
-    if( !pPager->tempFile && pPager->hasHeldSharedLock ){
-      /* The shared-lock has just been acquired then check to
-      ** see if the database has been modified.  If the database has changed,
-      ** flush the cache.  The hasHeldSharedLock flag prevents this from
-      ** occurring on the very first access to a file, in order to save a
-      ** single unnecessary sqlite3OsRead() call at the start-up.
-      **
-      ** Database changes are detected by looking at 15 bytes beginning
-      ** at offset 24 into the file.  The first 4 of these 16 bytes are
-      ** a 32-bit counter that is incremented with each change.  The
-      ** other bytes change randomly with each file change when
-      ** a codec is in use.
-      ** 
-      ** There is a vanishingly small chance that a change will not be 
-      ** detected.  The chance of an undetected change is so small that
-      ** it can be neglected.
-      */
-      Pgno nPage = 0;
-      char dbFileVers[sizeof(pPager->dbFileVers)];
-
-      rc = pagerPagecount(pPager, &nPage);
-      if( rc ) goto failed;
-
-      if( nPage>0 ){
-        IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
-        rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
-        if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
-          goto failed;
-        }
-      }else{
-        memset(dbFileVers, 0, sizeof(dbFileVers));
-      }
-
-      if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
-        pager_reset(pPager);
-
-        /* Unmap the database file. It is possible that external processes
-        ** may have truncated the database file and then extended it back
-        ** to its original size while this process was not holding a lock.
-        ** In this case there may exist a Pager.pMap mapping that appears
-        ** to be the right size but is not actually valid. Avoid this
-        ** possibility by unmapping the db here. */
-        if( USEFETCH(pPager) ){
-          sqlite3OsUnfetch(pPager->fd, 0, 0);
-        }
-      }
-    }
-
-    /* If there is a WAL file in the file-system, open this database in WAL
-    ** mode. Otherwise, the following function call is a no-op.
-    */
-    rc = pagerOpenWalIfPresent(pPager);
-#ifndef SQLITE_OMIT_WAL
-    assert( pPager->pWal==0 || rc==SQLITE_OK );
-#endif
-  }
-
-  if( pagerUseWal(pPager) ){
-    assert( rc==SQLITE_OK );
-    rc = pagerBeginReadTransaction(pPager);
-  }
-
-  if( pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){
-    rc = pagerPagecount(pPager, &pPager->dbSize);
-  }
-
- failed:
-  if( rc!=SQLITE_OK ){
-    assert( !MEMDB );
-    pager_unlock(pPager);
-    assert( pPager->eState==PAGER_OPEN );
-  }else{
-    pPager->eState = PAGER_READER;
-    pPager->hasHeldSharedLock = 1;
-  }
-  return rc;
-}
-
-/*
-** If the reference count has reached zero, rollback any active
-** transaction and unlock the pager.
-**
-** Except, in locking_mode=EXCLUSIVE when there is nothing to in
-** the rollback journal, the unlock is not performed and there is
-** nothing to rollback, so this routine is a no-op.
-*/ 
-static void pagerUnlockIfUnused(Pager *pPager){
-  if( pPager->nMmapOut==0 && (sqlite3PcacheRefCount(pPager->pPCache)==0) ){
-    pagerUnlockAndRollback(pPager);
-  }
-}
-
-/*
-** Acquire a reference to page number pgno in pager pPager (a page
-** reference has type DbPage*). If the requested reference is 
-** successfully obtained, it is copied to *ppPage and SQLITE_OK returned.
-**
-** If the requested page is already in the cache, it is returned. 
-** Otherwise, a new page object is allocated and populated with data
-** read from the database file. In some cases, the pcache module may
-** choose not to allocate a new page object and may reuse an existing
-** object with no outstanding references.
-**
-** The extra data appended to a page is always initialized to zeros the 
-** first time a page is loaded into memory. If the page requested is 
-** already in the cache when this function is called, then the extra
-** data is left as it was when the page object was last used.
-**
-** If the database image is smaller than the requested page or if a 
-** non-zero value is passed as the noContent parameter and the 
-** requested page is not already stored in the cache, then no 
-** actual disk read occurs. In this case the memory image of the 
-** page is initialized to all zeros. 
-**
-** If noContent is true, it means that we do not care about the contents
-** of the page. This occurs in two scenarios:
-**
-**   a) When reading a free-list leaf page from the database, and
-**
-**   b) When a savepoint is being rolled back and we need to load
-**      a new page into the cache to be filled with the data read
-**      from the savepoint journal.
-**
-** If noContent is true, then the data returned is zeroed instead of
-** being read from the database. Additionally, the bits corresponding
-** to pgno in Pager.pInJournal (bitvec of pages already written to the
-** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
-** savepoints are set. This means if the page is made writable at any
-** point in the future, using a call to sqlite3PagerWrite(), its contents
-** will not be journaled. This saves IO.
-**
-** The acquisition might fail for several reasons.  In all cases,
-** an appropriate error code is returned and *ppPage is set to NULL.
-**
-** See also sqlite3PagerLookup().  Both this routine and Lookup() attempt
-** to find a page in the in-memory cache first.  If the page is not already
-** in memory, this routine goes to disk to read it in whereas Lookup()
-** just returns 0.  This routine acquires a read-lock the first time it
-** has to go to disk, and could also playback an old journal if necessary.
-** Since Lookup() never goes to disk, it never has to deal with locks
-** or journal files.
-*/
-int sqlite3PagerAcquire(
-  Pager *pPager,      /* The pager open on the database file */
-  Pgno pgno,          /* Page number to fetch */
-  DbPage **ppPage,    /* Write a pointer to the page here */
-  int flags           /* PAGER_GET_XXX flags */
-){
-  int rc = SQLITE_OK;
-  PgHdr *pPg = 0;
-  u32 iFrame = 0;                 /* Frame to read from WAL file */
-  const int noContent = (flags & PAGER_GET_NOCONTENT);
-
-  /* It is acceptable to use a read-only (mmap) page for any page except
-  ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
-  ** flag was specified by the caller. And so long as the db is not a 
-  ** temporary or in-memory database.  */
-  const int bMmapOk = (pgno>1 && USEFETCH(pPager)
-   && (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY))
-#ifdef SQLITE_HAS_CODEC
-   && pPager->xCodec==0
-#endif
-  );
-
-  /* Optimization note:  Adding the "pgno<=1" term before "pgno==0" here
-  ** allows the compiler optimizer to reuse the results of the "pgno>1"
-  ** test in the previous statement, and avoid testing pgno==0 in the
-  ** common case where pgno is large. */
-  if( pgno<=1 && pgno==0 ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  assert( pPager->eState>=PAGER_READER );
-  assert( assert_pager_state(pPager) );
-  assert( noContent==0 || bMmapOk==0 );
-
-  assert( pPager->hasHeldSharedLock==1 );
-
-  /* If the pager is in the error state, return an error immediately. 
-  ** Otherwise, request the page from the PCache layer. */
-  if( pPager->errCode!=SQLITE_OK ){
-    rc = pPager->errCode;
-  }else{
-    if( bMmapOk && pagerUseWal(pPager) ){
-      rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
-      if( rc!=SQLITE_OK ) goto pager_acquire_err;
-    }
-
-    if( bMmapOk && iFrame==0 ){
-      void *pData = 0;
-
-      rc = sqlite3OsFetch(pPager->fd, 
-          (i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData
-      );
-
-      if( rc==SQLITE_OK && pData ){
-        if( pPager->eState>PAGER_READER ){
-          pPg = sqlite3PagerLookup(pPager, pgno);
-        }
-        if( pPg==0 ){
-          rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg);
-        }else{
-          sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData);
-        }
-        if( pPg ){
-          assert( rc==SQLITE_OK );
-          *ppPage = pPg;
-          return SQLITE_OK;
-        }
-      }
-      if( rc!=SQLITE_OK ){
-        goto pager_acquire_err;
-      }
-    }
-
-    {
-      sqlite3_pcache_page *pBase;
-      pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
-      if( pBase==0 ){
-        rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
-        if( rc!=SQLITE_OK ) goto pager_acquire_err;
-        if( pBase==0 ){
-          pPg = *ppPage = 0;
-          rc = SQLITE_NOMEM;
-          goto pager_acquire_err;
-        }
-      }
-      pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
-      assert( pPg!=0 );
-    }
-  }
-
-  if( rc!=SQLITE_OK ){
-    /* Either the call to sqlite3PcacheFetch() returned an error or the
-    ** pager was already in the error-state when this function was called.
-    ** Set pPg to 0 and jump to the exception handler.  */
-    pPg = 0;
-    goto pager_acquire_err;
-  }
-  assert( pPg==(*ppPage) );
-  assert( pPg->pgno==pgno );
-  assert( pPg->pPager==pPager || pPg->pPager==0 );
-
-  if( pPg->pPager && !noContent ){
-    /* In this case the pcache already contains an initialized copy of
-    ** the page. Return without further ado.  */
-    assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) );
-    pPager->aStat[PAGER_STAT_HIT]++;
-    return SQLITE_OK;
-
-  }else{
-    /* The pager cache has created a new page. Its content needs to 
-    ** be initialized.  */
-
-    pPg->pPager = pPager;
-
-    /* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
-    ** number greater than this, or the unused locking-page, is requested. */
-    if( pgno>PAGER_MAX_PGNO || pgno==PAGER_MJ_PGNO(pPager) ){
-      rc = SQLITE_CORRUPT_BKPT;
-      goto pager_acquire_err;
-    }
-
-    if( MEMDB || pPager->dbSize<pgno || noContent || !isOpen(pPager->fd) ){
-      if( pgno>pPager->mxPgno ){
-        rc = SQLITE_FULL;
-        goto pager_acquire_err;
-      }
-      if( noContent ){
-        /* Failure to set the bits in the InJournal bit-vectors is benign.
-        ** It merely means that we might do some extra work to journal a 
-        ** page that does not need to be journaled.  Nevertheless, be sure 
-        ** to test the case where a malloc error occurs while trying to set 
-        ** a bit in a bit vector.
-        */
-        sqlite3BeginBenignMalloc();
-        if( pgno<=pPager->dbOrigSize ){
-          TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno);
-          testcase( rc==SQLITE_NOMEM );
-        }
-        TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno);
-        testcase( rc==SQLITE_NOMEM );
-        sqlite3EndBenignMalloc();
-      }
-      memset(pPg->pData, 0, pPager->pageSize);
-      IOTRACE(("ZERO %p %d\n", pPager, pgno));
-    }else{
-      if( pagerUseWal(pPager) && bMmapOk==0 ){
-        rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
-        if( rc!=SQLITE_OK ) goto pager_acquire_err;
-      }
-      assert( pPg->pPager==pPager );
-      pPager->aStat[PAGER_STAT_MISS]++;
-      rc = readDbPage(pPg, iFrame);
-      if( rc!=SQLITE_OK ){
-        goto pager_acquire_err;
-      }
-    }
-    pager_set_pagehash(pPg);
-  }
-
-  return SQLITE_OK;
-
-pager_acquire_err:
-  assert( rc!=SQLITE_OK );
-  if( pPg ){
-    sqlite3PcacheDrop(pPg);
-  }
-  pagerUnlockIfUnused(pPager);
-
-  *ppPage = 0;
-  return rc;
-}
-
-/*
-** Acquire a page if it is already in the in-memory cache.  Do
-** not read the page from disk.  Return a pointer to the page,
-** or 0 if the page is not in cache. 
-**
-** See also sqlite3PagerGet().  The difference between this routine
-** and sqlite3PagerGet() is that _get() will go to the disk and read
-** in the page if the page is not already in cache.  This routine
-** returns NULL if the page is not in cache or if a disk I/O error 
-** has ever happened.
-*/
-DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
-  sqlite3_pcache_page *pPage;
-  assert( pPager!=0 );
-  assert( pgno!=0 );
-  assert( pPager->pPCache!=0 );
-  pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0);
-  assert( pPage==0 || pPager->hasHeldSharedLock );
-  if( pPage==0 ) return 0;
-  return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage);
-}
-
-/*
-** Release a page reference.
-**
-** If the number of references to the page drop to zero, then the
-** page is added to the LRU list.  When all references to all pages
-** are released, a rollback occurs and the lock on the database is
-** removed.
-*/
-void sqlite3PagerUnrefNotNull(DbPage *pPg){
-  Pager *pPager;
-  assert( pPg!=0 );
-  pPager = pPg->pPager;
-  if( pPg->flags & PGHDR_MMAP ){
-    pagerReleaseMapPage(pPg);
-  }else{
-    sqlite3PcacheRelease(pPg);
-  }
-  pagerUnlockIfUnused(pPager);
-}
-void sqlite3PagerUnref(DbPage *pPg){
-  if( pPg ) sqlite3PagerUnrefNotNull(pPg);
-}
-
-/*
-** This function is called at the start of every write transaction.
-** There must already be a RESERVED or EXCLUSIVE lock on the database 
-** file when this routine is called.
-**
-** Open the journal file for pager pPager and write a journal header
-** to the start of it. If there are active savepoints, open the sub-journal
-** as well. This function is only used when the journal file is being 
-** opened to write a rollback log for a transaction. It is not used 
-** when opening a hot journal file to roll it back.
-**
-** If the journal file is already open (as it may be in exclusive mode),
-** then this function just writes a journal header to the start of the
-** already open file. 
-**
-** Whether or not the journal file is opened by this function, the
-** Pager.pInJournal bitvec structure is allocated.
-**
-** Return SQLITE_OK if everything is successful. Otherwise, return 
-** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or 
-** an IO error code if opening or writing the journal file fails.
-*/
-static int pager_open_journal(Pager *pPager){
-  int rc = SQLITE_OK;                        /* Return code */
-  sqlite3_vfs * const pVfs = pPager->pVfs;   /* Local cache of vfs pointer */
-
-  assert( pPager->eState==PAGER_WRITER_LOCKED );
-  assert( assert_pager_state(pPager) );
-  assert( pPager->pInJournal==0 );
-  
-  /* If already in the error state, this function is a no-op.  But on
-  ** the other hand, this routine is never called if we are already in
-  ** an error state. */
-  if( NEVER(pPager->errCode) ) return pPager->errCode;
-
-  if( !pagerUseWal(pPager) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
-    pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
-    if( pPager->pInJournal==0 ){
-      return SQLITE_NOMEM;
-    }
-  
-    /* Open the journal file if it is not already open. */
-    if( !isOpen(pPager->jfd) ){
-      if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
-        sqlite3MemJournalOpen(pPager->jfd);
-      }else{
-        const int flags =                   /* VFS flags to open journal file */
-          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
-          (pPager->tempFile ? 
-            (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL):
-            (SQLITE_OPEN_MAIN_JOURNAL)
-          );
-
-        /* Verify that the database still has the same name as it did when
-        ** it was originally opened. */
-        rc = databaseIsUnmoved(pPager);
-        if( rc==SQLITE_OK ){
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-          rc = sqlite3JournalOpen(
-              pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)
-          );
-#else
-          rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
-#endif
-        }
-      }
-      assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
-    }
-  
-  
-    /* Write the first journal header to the journal file and open 
-    ** the sub-journal if necessary.
-    */
-    if( rc==SQLITE_OK ){
-      /* TODO: Check if all of these are really required. */
-      pPager->nRec = 0;
-      pPager->journalOff = 0;
-      pPager->setMaster = 0;
-      pPager->journalHdr = 0;
-      rc = writeJournalHdr(pPager);
-    }
-  }
-
-  if( rc!=SQLITE_OK ){
-    sqlite3BitvecDestroy(pPager->pInJournal);
-    pPager->pInJournal = 0;
-  }else{
-    assert( pPager->eState==PAGER_WRITER_LOCKED );
-    pPager->eState = PAGER_WRITER_CACHEMOD;
-  }
-
-  return rc;
-}
-
-/*
-** Begin a write-transaction on the specified pager object. If a 
-** write-transaction has already been opened, this function is a no-op.
-**
-** If the exFlag argument is false, then acquire at least a RESERVED
-** lock on the database file. If exFlag is true, then acquire at least
-** an EXCLUSIVE lock. If such a lock is already held, no locking 
-** functions need be called.
-**
-** If the subjInMemory argument is non-zero, then any sub-journal opened
-** within this transaction will be opened as an in-memory file. This
-** has no effect if the sub-journal is already opened (as it may be when
-** running in exclusive mode) or if the transaction does not require a
-** sub-journal. If the subjInMemory argument is zero, then any required
-** sub-journal is implemented in-memory if pPager is an in-memory database, 
-** or using a temporary file otherwise.
-*/
-int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
-  int rc = SQLITE_OK;
-
-  if( pPager->errCode ) return pPager->errCode;
-  assert( pPager->eState>=PAGER_READER && pPager->eState<PAGER_ERROR );
-  pPager->subjInMemory = (u8)subjInMemory;
-
-  if( ALWAYS(pPager->eState==PAGER_READER) ){
-    assert( pPager->pInJournal==0 );
-
-    if( pagerUseWal(pPager) ){
-      /* If the pager is configured to use locking_mode=exclusive, and an
-      ** exclusive lock on the database is not already held, obtain it now.
-      */
-      if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){
-        rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
-        if( rc!=SQLITE_OK ){
-          return rc;
-        }
-        sqlite3WalExclusiveMode(pPager->pWal, 1);
-      }
-
-      /* Grab the write lock on the log file. If successful, upgrade to
-      ** PAGER_RESERVED state. Otherwise, return an error code to the caller.
-      ** The busy-handler is not invoked if another connection already
-      ** holds the write-lock. If possible, the upper layer will call it.
-      */
-      rc = sqlite3WalBeginWriteTransaction(pPager->pWal);
-    }else{
-      /* Obtain a RESERVED lock on the database file. If the exFlag parameter
-      ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
-      ** busy-handler callback can be used when upgrading to the EXCLUSIVE
-      ** lock, but not when obtaining the RESERVED lock.
-      */
-      rc = pagerLockDb(pPager, RESERVED_LOCK);
-      if( rc==SQLITE_OK && exFlag ){
-        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
-      }
-    }
-
-    if( rc==SQLITE_OK ){
-      /* Change to WRITER_LOCKED state.
-      **
-      ** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD
-      ** when it has an open transaction, but never to DBMOD or FINISHED.
-      ** This is because in those states the code to roll back savepoint 
-      ** transactions may copy data from the sub-journal into the database 
-      ** file as well as into the page cache. Which would be incorrect in 
-      ** WAL mode.
-      */
-      pPager->eState = PAGER_WRITER_LOCKED;
-      pPager->dbHintSize = pPager->dbSize;
-      pPager->dbFileSize = pPager->dbSize;
-      pPager->dbOrigSize = pPager->dbSize;
-      pPager->journalOff = 0;
-    }
-
-    assert( rc==SQLITE_OK || pPager->eState==PAGER_READER );
-    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
-    assert( assert_pager_state(pPager) );
-  }
-
-  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
-  return rc;
-}
-
-/*
-** Write page pPg onto the end of the rollback journal.
-*/
-static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  int rc;
-  u32 cksum;
-  char *pData2;
-  i64 iOff = pPager->journalOff;
-
-  /* We should never write to the journal file the page that
-  ** contains the database locks.  The following assert verifies
-  ** that we do not. */
-  assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
-
-  assert( pPager->journalHdr<=pPager->journalOff );
-  CODEC2(pPager, pPg->pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
-  cksum = pager_cksum(pPager, (u8*)pData2);
-
-  /* Even if an IO or diskfull error occurs while journalling the
-  ** page in the block above, set the need-sync flag for the page.
-  ** Otherwise, when the transaction is rolled back, the logic in
-  ** playback_one_page() will think that the page needs to be restored
-  ** in the database file. And if an IO error occurs while doing so,
-  ** then corruption may follow.
-  */
-  pPg->flags |= PGHDR_NEED_SYNC;
-
-  rc = write32bits(pPager->jfd, iOff, pPg->pgno);
-  if( rc!=SQLITE_OK ) return rc;
-  rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
-  if( rc!=SQLITE_OK ) return rc;
-  rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
-  if( rc!=SQLITE_OK ) return rc;
-
-  IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
-           pPager->journalOff, pPager->pageSize));
-  PAGER_INCR(sqlite3_pager_writej_count);
-  PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
-       PAGERID(pPager), pPg->pgno, 
-       ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
-
-  pPager->journalOff += 8 + pPager->pageSize;
-  pPager->nRec++;
-  assert( pPager->pInJournal!=0 );
-  rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
-  testcase( rc==SQLITE_NOMEM );
-  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
-  rc |= addToSavepointBitvecs(pPager, pPg->pgno);
-  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
-  return rc;
-}
-
-/*
-** Mark a single data page as writeable. The page is written into the 
-** main journal or sub-journal as required. If the page is written into
-** one of the journals, the corresponding bit is set in the 
-** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
-** of any open savepoints as appropriate.
-*/
-static int pager_write(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  int rc = SQLITE_OK;
-
-  /* This routine is not called unless a write-transaction has already 
-  ** been started. The journal file may or may not be open at this point.
-  ** It is never called in the ERROR state.
-  */
-  assert( pPager->eState==PAGER_WRITER_LOCKED
-       || pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-  );
-  assert( assert_pager_state(pPager) );
-  assert( pPager->errCode==0 );
-  assert( pPager->readOnly==0 );
-  CHECK_PAGE(pPg);
-
-  /* The journal file needs to be opened. Higher level routines have already
-  ** obtained the necessary locks to begin the write-transaction, but the
-  ** rollback journal might not yet be open. Open it now if this is the case.
-  **
-  ** This is done before calling sqlite3PcacheMakeDirty() on the page. 
-  ** Otherwise, if it were done after calling sqlite3PcacheMakeDirty(), then
-  ** an error might occur and the pager would end up in WRITER_LOCKED state
-  ** with pages marked as dirty in the cache.
-  */
-  if( pPager->eState==PAGER_WRITER_LOCKED ){
-    rc = pager_open_journal(pPager);
-    if( rc!=SQLITE_OK ) return rc;
-  }
-  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
-  assert( assert_pager_state(pPager) );
-
-  /* Mark the page that is about to be modified as dirty. */
-  sqlite3PcacheMakeDirty(pPg);
-
-  /* If a rollback journal is in use, them make sure the page that is about
-  ** to change is in the rollback journal, or if the page is a new page off
-  ** then end of the file, make sure it is marked as PGHDR_NEED_SYNC.
-  */
-  assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) );
-  if( pPager->pInJournal!=0
-   && sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0
-  ){
-    assert( pagerUseWal(pPager)==0 );
-    if( pPg->pgno<=pPager->dbOrigSize ){
-      rc = pagerAddPageToRollbackJournal(pPg);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-    }else{
-      if( pPager->eState!=PAGER_WRITER_DBMOD ){
-        pPg->flags |= PGHDR_NEED_SYNC;
-      }
-      PAGERTRACE(("APPEND %d page %d needSync=%d\n",
-              PAGERID(pPager), pPg->pgno,
-             ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
-    }
-  }
-
-  /* The PGHDR_DIRTY bit is set above when the page was added to the dirty-list
-  ** and before writing the page into the rollback journal.  Wait until now,
-  ** after the page has been successfully journalled, before setting the
-  ** PGHDR_WRITEABLE bit that indicates that the page can be safely modified.
-  */
-  pPg->flags |= PGHDR_WRITEABLE;
-  
-  /* If the statement journal is open and the page is not in it,
-  ** then write the page into the statement journal.
-  */
-  if( pPager->nSavepoint>0 ){
-    rc = subjournalPageIfRequired(pPg);
-  }
-
-  /* Update the database size and return. */
-  if( pPager->dbSize<pPg->pgno ){
-    pPager->dbSize = pPg->pgno;
-  }
-  return rc;
-}
-
-/*
-** This is a variant of sqlite3PagerWrite() that runs when the sector size
-** is larger than the page size.  SQLite makes the (reasonable) assumption that
-** all bytes of a sector are written together by hardware.  Hence, all bytes of
-** a sector need to be journalled in case of a power loss in the middle of
-** a write.
-**
-** Usually, the sector size is less than or equal to the page size, in which
-** case pages can be individually written.  This routine only runs in the
-** exceptional case where the page size is smaller than the sector size.
-*/
-static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){
-  int rc = SQLITE_OK;          /* Return code */
-  Pgno nPageCount;             /* Total number of pages in database file */
-  Pgno pg1;                    /* First page of the sector pPg is located on. */
-  int nPage = 0;               /* Number of pages starting at pg1 to journal */
-  int ii;                      /* Loop counter */
-  int needSync = 0;            /* True if any page has PGHDR_NEED_SYNC */
-  Pager *pPager = pPg->pPager; /* The pager that owns pPg */
-  Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
-
-  /* Set the doNotSpill NOSYNC bit to 1. This is because we cannot allow
-  ** a journal header to be written between the pages journaled by
-  ** this function.
-  */
-  assert( !MEMDB );
-  assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)==0 );
-  pPager->doNotSpill |= SPILLFLAG_NOSYNC;
-
-  /* This trick assumes that both the page-size and sector-size are
-  ** an integer power of 2. It sets variable pg1 to the identifier
-  ** of the first page of the sector pPg is located on.
-  */
-  pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
-
-  nPageCount = pPager->dbSize;
-  if( pPg->pgno>nPageCount ){
-    nPage = (pPg->pgno - pg1)+1;
-  }else if( (pg1+nPagePerSector-1)>nPageCount ){
-    nPage = nPageCount+1-pg1;
-  }else{
-    nPage = nPagePerSector;
-  }
-  assert(nPage>0);
-  assert(pg1<=pPg->pgno);
-  assert((pg1+nPage)>pPg->pgno);
-
-  for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
-    Pgno pg = pg1+ii;
-    PgHdr *pPage;
-    if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
-      if( pg!=PAGER_MJ_PGNO(pPager) ){
-        rc = sqlite3PagerGet(pPager, pg, &pPage);
-        if( rc==SQLITE_OK ){
-          rc = pager_write(pPage);
-          if( pPage->flags&PGHDR_NEED_SYNC ){
-            needSync = 1;
-          }
-          sqlite3PagerUnrefNotNull(pPage);
-        }
-      }
-    }else if( (pPage = sqlite3PagerLookup(pPager, pg))!=0 ){
-      if( pPage->flags&PGHDR_NEED_SYNC ){
-        needSync = 1;
-      }
-      sqlite3PagerUnrefNotNull(pPage);
-    }
-  }
-
-  /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages 
-  ** starting at pg1, then it needs to be set for all of them. Because
-  ** writing to any of these nPage pages may damage the others, the
-  ** journal file must contain sync()ed copies of all of them
-  ** before any of them can be written out to the database file.
-  */
-  if( rc==SQLITE_OK && needSync ){
-    assert( !MEMDB );
-    for(ii=0; ii<nPage; ii++){
-      PgHdr *pPage = sqlite3PagerLookup(pPager, pg1+ii);
-      if( pPage ){
-        pPage->flags |= PGHDR_NEED_SYNC;
-        sqlite3PagerUnrefNotNull(pPage);
-      }
-    }
-  }
-
-  assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)!=0 );
-  pPager->doNotSpill &= ~SPILLFLAG_NOSYNC;
-  return rc;
-}
-
-/*
-** Mark a data page as writeable. This routine must be called before 
-** making changes to a page. The caller must check the return value 
-** of this function and be careful not to change any page data unless 
-** this routine returns SQLITE_OK.
-**
-** The difference between this function and pager_write() is that this
-** function also deals with the special case where 2 or more pages
-** fit on a single disk sector. In this case all co-resident pages
-** must have been written to the journal file before returning.
-**
-** If an error occurs, SQLITE_NOMEM or an IO error code is returned
-** as appropriate. Otherwise, SQLITE_OK.
-*/
-int sqlite3PagerWrite(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  assert( (pPg->flags & PGHDR_MMAP)==0 );
-  assert( pPager->eState>=PAGER_WRITER_LOCKED );
-  assert( pPager->eState!=PAGER_ERROR );
-  assert( assert_pager_state(pPager) );
-  if( (pPg->flags & PGHDR_WRITEABLE)!=0 && pPager->dbSize>=pPg->pgno ){
-    if( pPager->nSavepoint ) return subjournalPageIfRequired(pPg);
-    return SQLITE_OK;
-  }else if( pPager->sectorSize > (u32)pPager->pageSize ){
-    return pagerWriteLargeSector(pPg);
-  }else{
-    return pager_write(pPg);
-  }
-}
-
-/*
-** Return TRUE if the page given in the argument was previously passed
-** to sqlite3PagerWrite().  In other words, return TRUE if it is ok
-** to change the content of the page.
-*/
-#ifndef NDEBUG
-int sqlite3PagerIswriteable(DbPage *pPg){
-  return pPg->flags & PGHDR_WRITEABLE;
-}
-#endif
-
-/*
-** A call to this routine tells the pager that it is not necessary to
-** write the information on page pPg back to the disk, even though
-** that page might be marked as dirty.  This happens, for example, when
-** the page has been added as a leaf of the freelist and so its
-** content no longer matters.
-**
-** The overlying software layer calls this routine when all of the data
-** on the given page is unused. The pager marks the page as clean so
-** that it does not get written to disk.
-**
-** Tests show that this optimization can quadruple the speed of large 
-** DELETE operations.
-*/
-void sqlite3PagerDontWrite(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  if( (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
-    PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
-    IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
-    pPg->flags |= PGHDR_DONT_WRITE;
-    pPg->flags &= ~PGHDR_WRITEABLE;
-    pager_set_pagehash(pPg);
-  }
-}
-
-/*
-** This routine is called to increment the value of the database file 
-** change-counter, stored as a 4-byte big-endian integer starting at 
-** byte offset 24 of the pager file.  The secondary change counter at
-** 92 is also updated, as is the SQLite version number at offset 96.
-**
-** But this only happens if the pPager->changeCountDone flag is false.
-** To avoid excess churning of page 1, the update only happens once.
-** See also the pager_write_changecounter() routine that does an 
-** unconditional update of the change counters.
-**
-** If the isDirectMode flag is zero, then this is done by calling 
-** sqlite3PagerWrite() on page 1, then modifying the contents of the
-** page data. In this case the file will be updated when the current
-** transaction is committed.
-**
-** The isDirectMode flag may only be non-zero if the library was compiled
-** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case,
-** if isDirect is non-zero, then the database file is updated directly
-** by writing an updated version of page 1 using a call to the 
-** sqlite3OsWrite() function.
-*/
-static int pager_incr_changecounter(Pager *pPager, int isDirectMode){
-  int rc = SQLITE_OK;
-
-  assert( pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-  );
-  assert( assert_pager_state(pPager) );
-
-  /* Declare and initialize constant integer 'isDirect'. If the
-  ** atomic-write optimization is enabled in this build, then isDirect
-  ** is initialized to the value passed as the isDirectMode parameter
-  ** to this function. Otherwise, it is always set to zero.
-  **
-  ** The idea is that if the atomic-write optimization is not
-  ** enabled at compile time, the compiler can omit the tests of
-  ** 'isDirect' below, as well as the block enclosed in the
-  ** "if( isDirect )" condition.
-  */
-#ifndef SQLITE_ENABLE_ATOMIC_WRITE
-# define DIRECT_MODE 0
-  assert( isDirectMode==0 );
-  UNUSED_PARAMETER(isDirectMode);
-#else
-# define DIRECT_MODE isDirectMode
-#endif
-
-  if( !pPager->changeCountDone && ALWAYS(pPager->dbSize>0) ){
-    PgHdr *pPgHdr;                /* Reference to page 1 */
-
-    assert( !pPager->tempFile && isOpen(pPager->fd) );
-
-    /* Open page 1 of the file for writing. */
-    rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
-    assert( pPgHdr==0 || rc==SQLITE_OK );
-
-    /* If page one was fetched successfully, and this function is not
-    ** operating in direct-mode, make page 1 writable.  When not in 
-    ** direct mode, page 1 is always held in cache and hence the PagerGet()
-    ** above is always successful - hence the ALWAYS on rc==SQLITE_OK.
-    */
-    if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){
-      rc = sqlite3PagerWrite(pPgHdr);
-    }
-
-    if( rc==SQLITE_OK ){
-      /* Actually do the update of the change counter */
-      pager_write_changecounter(pPgHdr);
-
-      /* If running in direct mode, write the contents of page 1 to the file. */
-      if( DIRECT_MODE ){
-        const void *zBuf;
-        assert( pPager->dbFileSize>0 );
-        CODEC2(pPager, pPgHdr->pData, 1, 6, rc=SQLITE_NOMEM, zBuf);
-        if( rc==SQLITE_OK ){
-          rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
-          pPager->aStat[PAGER_STAT_WRITE]++;
-        }
-        if( rc==SQLITE_OK ){
-          /* Update the pager's copy of the change-counter. Otherwise, the
-          ** next time a read transaction is opened the cache will be
-          ** flushed (as the change-counter values will not match).  */
-          const void *pCopy = (const void *)&((const char *)zBuf)[24];
-          memcpy(&pPager->dbFileVers, pCopy, sizeof(pPager->dbFileVers));
-          pPager->changeCountDone = 1;
-        }
-      }else{
-        pPager->changeCountDone = 1;
-      }
-    }
-
-    /* Release the page reference. */
-    sqlite3PagerUnref(pPgHdr);
-  }
-  return rc;
-}
-
-/*
-** Sync the database file to disk. This is a no-op for in-memory databases
-** or pages with the Pager.noSync flag set.
-**
-** If successful, or if called on a pager for which it is a no-op, this
-** function returns SQLITE_OK. Otherwise, an IO error code is returned.
-*/
-int sqlite3PagerSync(Pager *pPager, const char *zMaster){
-  int rc = SQLITE_OK;
-
-  if( isOpen(pPager->fd) ){
-    void *pArg = (void*)zMaster;
-    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg);
-    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
-  }
-  if( rc==SQLITE_OK && !pPager->noSync ){
-    assert( !MEMDB );
-    rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
-  }
-  return rc;
-}
-
-/*
-** This function may only be called while a write-transaction is active in
-** rollback. If the connection is in WAL mode, this call is a no-op. 
-** Otherwise, if the connection does not already have an EXCLUSIVE lock on 
-** the database file, an attempt is made to obtain one.
-**
-** If the EXCLUSIVE lock is already held or the attempt to obtain it is
-** successful, or the connection is in WAL mode, SQLITE_OK is returned.
-** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is 
-** returned.
-*/
-int sqlite3PagerExclusiveLock(Pager *pPager){
-  int rc = SQLITE_OK;
-  assert( pPager->eState==PAGER_WRITER_CACHEMOD 
-       || pPager->eState==PAGER_WRITER_DBMOD 
-       || pPager->eState==PAGER_WRITER_LOCKED 
-  );
-  assert( assert_pager_state(pPager) );
-  if( 0==pagerUseWal(pPager) ){
-    rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
-  }
-  return rc;
-}
-
-/*
-** Sync the database file for the pager pPager. zMaster points to the name
-** of a master journal file that should be written into the individual
-** journal file. zMaster may be NULL, which is interpreted as no master
-** journal (a single database transaction).
-**
-** This routine ensures that:
-**
-**   * The database file change-counter is updated,
-**   * the journal is synced (unless the atomic-write optimization is used),
-**   * all dirty pages are written to the database file, 
-**   * the database file is truncated (if required), and
-**   * the database file synced. 
-**
-** The only thing that remains to commit the transaction is to finalize 
-** (delete, truncate or zero the first part of) the journal file (or 
-** delete the master journal file if specified).
-**
-** Note that if zMaster==NULL, this does not overwrite a previous value
-** passed to an sqlite3PagerCommitPhaseOne() call.
-**
-** If the final parameter - noSync - is true, then the database file itself
-** is not synced. The caller must call sqlite3PagerSync() directly to
-** sync the database file before calling CommitPhaseTwo() to delete the
-** journal file in this case.
-*/
-int sqlite3PagerCommitPhaseOne(
-  Pager *pPager,                  /* Pager object */
-  const char *zMaster,            /* If not NULL, the master journal name */
-  int noSync                      /* True to omit the xSync on the db file */
-){
-  int rc = SQLITE_OK;             /* Return code */
-
-  assert( pPager->eState==PAGER_WRITER_LOCKED
-       || pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-       || pPager->eState==PAGER_ERROR
-  );
-  assert( assert_pager_state(pPager) );
-
-  /* If a prior error occurred, report that error again. */
-  if( NEVER(pPager->errCode) ) return pPager->errCode;
-
-  PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", 
-      pPager->zFilename, zMaster, pPager->dbSize));
-
-  /* If no database changes have been made, return early. */
-  if( pPager->eState<PAGER_WRITER_CACHEMOD ) return SQLITE_OK;
-
-  if( MEMDB ){
-    /* If this is an in-memory db, or no pages have been written to, or this
-    ** function has already been called, it is mostly a no-op.  However, any
-    ** backup in progress needs to be restarted.
-    */
-    sqlite3BackupRestart(pPager->pBackup);
-  }else{
-    if( pagerUseWal(pPager) ){
-      PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache);
-      PgHdr *pPageOne = 0;
-      if( pList==0 ){
-        /* Must have at least one page for the WAL commit flag.
-        ** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */
-        rc = sqlite3PagerGet(pPager, 1, &pPageOne);
-        pList = pPageOne;
-        pList->pDirty = 0;
-      }
-      assert( rc==SQLITE_OK );
-      if( ALWAYS(pList) ){
-        rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1);
-      }
-      sqlite3PagerUnref(pPageOne);
-      if( rc==SQLITE_OK ){
-        sqlite3PcacheCleanAll(pPager->pPCache);
-      }
-    }else{
-      /* The following block updates the change-counter. Exactly how it
-      ** does this depends on whether or not the atomic-update optimization
-      ** was enabled at compile time, and if this transaction meets the 
-      ** runtime criteria to use the operation: 
-      **
-      **    * The file-system supports the atomic-write property for
-      **      blocks of size page-size, and 
-      **    * This commit is not part of a multi-file transaction, and
-      **    * Exactly one page has been modified and store in the journal file.
-      **
-      ** If the optimization was not enabled at compile time, then the
-      ** pager_incr_changecounter() function is called to update the change
-      ** counter in 'indirect-mode'. If the optimization is compiled in but
-      ** is not applicable to this transaction, call sqlite3JournalCreate()
-      ** to make sure the journal file has actually been created, then call
-      ** pager_incr_changecounter() to update the change-counter in indirect
-      ** mode. 
-      **
-      ** Otherwise, if the optimization is both enabled and applicable,
-      ** then call pager_incr_changecounter() to update the change-counter
-      ** in 'direct' mode. In this case the journal file will never be
-      ** created for this transaction.
-      */
-  #ifdef SQLITE_ENABLE_ATOMIC_WRITE
-      PgHdr *pPg;
-      assert( isOpen(pPager->jfd) 
-           || pPager->journalMode==PAGER_JOURNALMODE_OFF 
-           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
-      );
-      if( !zMaster && isOpen(pPager->jfd) 
-       && pPager->journalOff==jrnlBufferSize(pPager) 
-       && pPager->dbSize>=pPager->dbOrigSize
-       && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
-      ){
-        /* Update the db file change counter via the direct-write method. The 
-        ** following call will modify the in-memory representation of page 1 
-        ** to include the updated change counter and then write page 1 
-        ** directly to the database file. Because of the atomic-write 
-        ** property of the host file-system, this is safe.
-        */
-        rc = pager_incr_changecounter(pPager, 1);
-      }else{
-        rc = sqlite3JournalCreate(pPager->jfd);
-        if( rc==SQLITE_OK ){
-          rc = pager_incr_changecounter(pPager, 0);
-        }
-      }
-  #else
-      rc = pager_incr_changecounter(pPager, 0);
-  #endif
-      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-  
-      /* Write the master journal name into the journal file. If a master 
-      ** journal file name has already been written to the journal file, 
-      ** or if zMaster is NULL (no master journal), then this call is a no-op.
-      */
-      rc = writeMasterJournal(pPager, zMaster);
-      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-  
-      /* Sync the journal file and write all dirty pages to the database.
-      ** If the atomic-update optimization is being used, this sync will not 
-      ** create the journal file or perform any real IO.
-      **
-      ** Because the change-counter page was just modified, unless the
-      ** atomic-update optimization is used it is almost certain that the
-      ** journal requires a sync here. However, in locking_mode=exclusive
-      ** on a system under memory pressure it is just possible that this is 
-      ** not the case. In this case it is likely enough that the redundant
-      ** xSync() call will be changed to a no-op by the OS anyhow. 
-      */
-      rc = syncJournal(pPager, 0);
-      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-  
-      rc = pager_write_pagelist(pPager,sqlite3PcacheDirtyList(pPager->pPCache));
-      if( rc!=SQLITE_OK ){
-        assert( rc!=SQLITE_IOERR_BLOCKED );
-        goto commit_phase_one_exit;
-      }
-      sqlite3PcacheCleanAll(pPager->pPCache);
-
-      /* If the file on disk is smaller than the database image, use 
-      ** pager_truncate to grow the file here. This can happen if the database
-      ** image was extended as part of the current transaction and then the
-      ** last page in the db image moved to the free-list. In this case the
-      ** last page is never written out to disk, leaving the database file
-      ** undersized. Fix this now if it is the case.  */
-      if( pPager->dbSize>pPager->dbFileSize ){
-        Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
-        assert( pPager->eState==PAGER_WRITER_DBMOD );
-        rc = pager_truncate(pPager, nNew);
-        if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-      }
-  
-      /* Finally, sync the database file. */
-      if( !noSync ){
-        rc = sqlite3PagerSync(pPager, zMaster);
-      }
-      IOTRACE(("DBSYNC %p\n", pPager))
-    }
-  }
-
-commit_phase_one_exit:
-  if( rc==SQLITE_OK && !pagerUseWal(pPager) ){
-    pPager->eState = PAGER_WRITER_FINISHED;
-  }
-  return rc;
-}
-
-
-/*
-** When this function is called, the database file has been completely
-** updated to reflect the changes made by the current transaction and
-** synced to disk. The journal file still exists in the file-system 
-** though, and if a failure occurs at this point it will eventually
-** be used as a hot-journal and the current transaction rolled back.
-**
-** This function finalizes the journal file, either by deleting, 
-** truncating or partially zeroing it, so that it cannot be used 
-** for hot-journal rollback. Once this is done the transaction is
-** irrevocably committed.
-**
-** If an error occurs, an IO error code is returned and the pager
-** moves into the error state. Otherwise, SQLITE_OK is returned.
-*/
-int sqlite3PagerCommitPhaseTwo(Pager *pPager){
-  int rc = SQLITE_OK;                  /* Return code */
-
-  /* This routine should not be called if a prior error has occurred.
-  ** But if (due to a coding error elsewhere in the system) it does get
-  ** called, just return the same error code without doing anything. */
-  if( NEVER(pPager->errCode) ) return pPager->errCode;
-
-  assert( pPager->eState==PAGER_WRITER_LOCKED
-       || pPager->eState==PAGER_WRITER_FINISHED
-       || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD)
-  );
-  assert( assert_pager_state(pPager) );
-
-  /* An optimization. If the database was not actually modified during
-  ** this transaction, the pager is running in exclusive-mode and is
-  ** using persistent journals, then this function is a no-op.
-  **
-  ** The start of the journal file currently contains a single journal 
-  ** header with the nRec field set to 0. If such a journal is used as
-  ** a hot-journal during hot-journal rollback, 0 changes will be made
-  ** to the database file. So there is no need to zero the journal 
-  ** header. Since the pager is in exclusive mode, there is no need
-  ** to drop any locks either.
-  */
-  if( pPager->eState==PAGER_WRITER_LOCKED 
-   && pPager->exclusiveMode 
-   && pPager->journalMode==PAGER_JOURNALMODE_PERSIST
-  ){
-    assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff );
-    pPager->eState = PAGER_READER;
-    return SQLITE_OK;
-  }
-
-  PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
-  pPager->iDataVersion++;
-  rc = pager_end_transaction(pPager, pPager->setMaster, 1);
-  return pager_error(pPager, rc);
-}
-
-/*
-** If a write transaction is open, then all changes made within the 
-** transaction are reverted and the current write-transaction is closed.
-** The pager falls back to PAGER_READER state if successful, or PAGER_ERROR
-** state if an error occurs.
-**
-** If the pager is already in PAGER_ERROR state when this function is called,
-** it returns Pager.errCode immediately. No work is performed in this case.
-**
-** Otherwise, in rollback mode, this function performs two functions:
-**
-**   1) It rolls back the journal file, restoring all database file and 
-**      in-memory cache pages to the state they were in when the transaction
-**      was opened, and
-**
-**   2) It finalizes the journal file, so that it is not used for hot
-**      rollback at any point in the future.
-**
-** Finalization of the journal file (task 2) is only performed if the 
-** rollback is successful.
-**
-** In WAL mode, all cache-entries containing data modified within the
-** current transaction are either expelled from the cache or reverted to
-** their pre-transaction state by re-reading data from the database or
-** WAL files. The WAL transaction is then closed.
-*/
-int sqlite3PagerRollback(Pager *pPager){
-  int rc = SQLITE_OK;                  /* Return code */
-  PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
-
-  /* PagerRollback() is a no-op if called in READER or OPEN state. If
-  ** the pager is already in the ERROR state, the rollback is not 
-  ** attempted here. Instead, the error code is returned to the caller.
-  */
-  assert( assert_pager_state(pPager) );
-  if( pPager->eState==PAGER_ERROR ) return pPager->errCode;
-  if( pPager->eState<=PAGER_READER ) return SQLITE_OK;
-
-  if( pagerUseWal(pPager) ){
-    int rc2;
-    rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
-    rc2 = pager_end_transaction(pPager, pPager->setMaster, 0);
-    if( rc==SQLITE_OK ) rc = rc2;
-  }else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){
-    int eState = pPager->eState;
-    rc = pager_end_transaction(pPager, 0, 0);
-    if( !MEMDB && eState>PAGER_WRITER_LOCKED ){
-      /* This can happen using journal_mode=off. Move the pager to the error 
-      ** state to indicate that the contents of the cache may not be trusted.
-      ** Any active readers will get SQLITE_ABORT.
-      */
-      pPager->errCode = SQLITE_ABORT;
-      pPager->eState = PAGER_ERROR;
-      return rc;
-    }
-  }else{
-    rc = pager_playback(pPager, 0);
-  }
-
-  assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK );
-  assert( rc==SQLITE_OK || rc==SQLITE_FULL || rc==SQLITE_CORRUPT
-          || rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR 
-          || rc==SQLITE_CANTOPEN
-  );
-
-  /* If an error occurs during a ROLLBACK, we can no longer trust the pager
-  ** cache. So call pager_error() on the way out to make any error persistent.
-  */
-  return pager_error(pPager, rc);
-}
-
-/*
-** Return TRUE if the database file is opened read-only.  Return FALSE
-** if the database is (in theory) writable.
-*/
-u8 sqlite3PagerIsreadonly(Pager *pPager){
-  return pPager->readOnly;
-}
-
-#ifdef SQLITE_DEBUG
-/*
-** Return the sum of the reference counts for all pages held by pPager.
-*/
-int sqlite3PagerRefcount(Pager *pPager){
-  return sqlite3PcacheRefCount(pPager->pPCache);
-}
-#endif
-
-/*
-** Return the approximate number of bytes of memory currently
-** used by the pager and its associated cache.
-*/
-int sqlite3PagerMemUsed(Pager *pPager){
-  int perPageSize = pPager->pageSize + pPager->nExtra + sizeof(PgHdr)
-                                     + 5*sizeof(void*);
-  return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
-           + sqlite3MallocSize(pPager)
-           + pPager->pageSize;
-}
-
-/*
-** Return the number of references to the specified page.
-*/
-int sqlite3PagerPageRefcount(DbPage *pPage){
-  return sqlite3PcachePageRefcount(pPage);
-}
-
-#ifdef SQLITE_TEST
-/*
-** This routine is used for testing and analysis only.
-*/
-int *sqlite3PagerStats(Pager *pPager){
-  static int a[11];
-  a[0] = sqlite3PcacheRefCount(pPager->pPCache);
-  a[1] = sqlite3PcachePagecount(pPager->pPCache);
-  a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
-  a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize;
-  a[4] = pPager->eState;
-  a[5] = pPager->errCode;
-  a[6] = pPager->aStat[PAGER_STAT_HIT];
-  a[7] = pPager->aStat[PAGER_STAT_MISS];
-  a[8] = 0;  /* Used to be pPager->nOvfl */
-  a[9] = pPager->nRead;
-  a[10] = pPager->aStat[PAGER_STAT_WRITE];
-  return a;
-}
-#endif
-
-/*
-** Parameter eStat must be either SQLITE_DBSTATUS_CACHE_HIT or
-** SQLITE_DBSTATUS_CACHE_MISS. Before returning, *pnVal is incremented by the
-** current cache hit or miss count, according to the value of eStat. If the 
-** reset parameter is non-zero, the cache hit or miss count is zeroed before 
-** returning.
-*/
-void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, int *pnVal){
-
-  assert( eStat==SQLITE_DBSTATUS_CACHE_HIT
-       || eStat==SQLITE_DBSTATUS_CACHE_MISS
-       || eStat==SQLITE_DBSTATUS_CACHE_WRITE
-  );
-
-  assert( SQLITE_DBSTATUS_CACHE_HIT+1==SQLITE_DBSTATUS_CACHE_MISS );
-  assert( SQLITE_DBSTATUS_CACHE_HIT+2==SQLITE_DBSTATUS_CACHE_WRITE );
-  assert( PAGER_STAT_HIT==0 && PAGER_STAT_MISS==1 && PAGER_STAT_WRITE==2 );
-
-  *pnVal += pPager->aStat[eStat - SQLITE_DBSTATUS_CACHE_HIT];
-  if( reset ){
-    pPager->aStat[eStat - SQLITE_DBSTATUS_CACHE_HIT] = 0;
-  }
-}
-
-/*
-** Return true if this is an in-memory pager.
-*/
-int sqlite3PagerIsMemdb(Pager *pPager){
-  return MEMDB;
-}
-
-/*
-** Check that there are at least nSavepoint savepoints open. If there are
-** currently less than nSavepoints open, then open one or more savepoints
-** to make up the difference. If the number of savepoints is already
-** equal to nSavepoint, then this function is a no-op.
-**
-** If a memory allocation fails, SQLITE_NOMEM is returned. If an error 
-** occurs while opening the sub-journal file, then an IO error code is
-** returned. Otherwise, SQLITE_OK.
-*/
-static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){
-  int rc = SQLITE_OK;                       /* Return code */
-  int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */
-  int ii;                                   /* Iterator variable */
-  PagerSavepoint *aNew;                     /* New Pager.aSavepoint array */
-
-  assert( pPager->eState>=PAGER_WRITER_LOCKED );
-  assert( assert_pager_state(pPager) );
-  assert( nSavepoint>nCurrent && pPager->useJournal );
-
-  /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
-  ** if the allocation fails. Otherwise, zero the new portion in case a 
-  ** malloc failure occurs while populating it in the for(...) loop below.
-  */
-  aNew = (PagerSavepoint *)sqlite3Realloc(
-      pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
-  );
-  if( !aNew ){
-    return SQLITE_NOMEM;
-  }
-  memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
-  pPager->aSavepoint = aNew;
-
-  /* Populate the PagerSavepoint structures just allocated. */
-  for(ii=nCurrent; ii<nSavepoint; ii++){
-    aNew[ii].nOrig = pPager->dbSize;
-    if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
-      aNew[ii].iOffset = pPager->journalOff;
-    }else{
-      aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
-    }
-    aNew[ii].iSubRec = pPager->nSubRec;
-    aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
-    if( !aNew[ii].pInSavepoint ){
-      return SQLITE_NOMEM;
-    }
-    if( pagerUseWal(pPager) ){
-      sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
-    }
-    pPager->nSavepoint = ii+1;
-  }
-  assert( pPager->nSavepoint==nSavepoint );
-  assertTruncateConstraint(pPager);
-  return rc;
-}
-int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
-  assert( pPager->eState>=PAGER_WRITER_LOCKED );
-  assert( assert_pager_state(pPager) );
-
-  if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){
-    return pagerOpenSavepoint(pPager, nSavepoint);
-  }else{
-    return SQLITE_OK;
-  }
-}
-
-
-/*
-** This function is called to rollback or release (commit) a savepoint.
-** The savepoint to release or rollback need not be the most recently 
-** created savepoint.
-**
-** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.
-** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with
-** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes
-** that have occurred since the specified savepoint was created.
-**
-** The savepoint to rollback or release is identified by parameter 
-** iSavepoint. A value of 0 means to operate on the outermost savepoint
-** (the first created). A value of (Pager.nSavepoint-1) means operate
-** on the most recently created savepoint. If iSavepoint is greater than
-** (Pager.nSavepoint-1), then this function is a no-op.
-**
-** If a negative value is passed to this function, then the current
-** transaction is rolled back. This is different to calling 
-** sqlite3PagerRollback() because this function does not terminate
-** the transaction or unlock the database, it just restores the 
-** contents of the database to its original state. 
-**
-** In any case, all savepoints with an index greater than iSavepoint 
-** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE),
-** then savepoint iSavepoint is also destroyed.
-**
-** This function may return SQLITE_NOMEM if a memory allocation fails,
-** or an IO error code if an IO error occurs while rolling back a 
-** savepoint. If no errors occur, SQLITE_OK is returned.
-*/ 
-int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
-  int rc = pPager->errCode;       /* Return code */
-
-  assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
-  assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK );
-
-  if( rc==SQLITE_OK && iSavepoint<pPager->nSavepoint ){
-    int ii;            /* Iterator variable */
-    int nNew;          /* Number of remaining savepoints after this op. */
-
-    /* Figure out how many savepoints will still be active after this
-    ** operation. Store this value in nNew. Then free resources associated 
-    ** with any savepoints that are destroyed by this operation.
-    */
-    nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1);
-    for(ii=nNew; ii<pPager->nSavepoint; ii++){
-      sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
-    }
-    pPager->nSavepoint = nNew;
-
-    /* If this is a release of the outermost savepoint, truncate 
-    ** the sub-journal to zero bytes in size. */
-    if( op==SAVEPOINT_RELEASE ){
-      if( nNew==0 && isOpen(pPager->sjfd) ){
-        /* Only truncate if it is an in-memory sub-journal. */
-        if( sqlite3IsMemJournal(pPager->sjfd) ){
-          rc = sqlite3OsTruncate(pPager->sjfd, 0);
-          assert( rc==SQLITE_OK );
-        }
-        pPager->nSubRec = 0;
-      }
-    }
-    /* Else this is a rollback operation, playback the specified savepoint.
-    ** If this is a temp-file, it is possible that the journal file has
-    ** not yet been opened. In this case there have been no changes to
-    ** the database file, so the playback operation can be skipped.
-    */
-    else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){
-      PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
-      rc = pagerPlaybackSavepoint(pPager, pSavepoint);
-      assert(rc!=SQLITE_DONE);
-    }
-  }
-
-  return rc;
-}
-
-/*
-** Return the full pathname of the database file.
-**
-** Except, if the pager is in-memory only, then return an empty string if
-** nullIfMemDb is true.  This routine is called with nullIfMemDb==1 when
-** used to report the filename to the user, for compatibility with legacy
-** behavior.  But when the Btree needs to know the filename for matching to
-** shared cache, it uses nullIfMemDb==0 so that in-memory databases can
-** participate in shared-cache.
-*/
-const char *sqlite3PagerFilename(Pager *pPager, int nullIfMemDb){
-  return (nullIfMemDb && pPager->memDb) ? "" : pPager->zFilename;
-}
-
-/*
-** Return the VFS structure for the pager.
-*/
-const sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
-  return pPager->pVfs;
-}
-
-/*
-** Return the file handle for the database file associated
-** with the pager.  This might return NULL if the file has
-** not yet been opened.
-*/
-sqlite3_file *sqlite3PagerFile(Pager *pPager){
-  return pPager->fd;
-}
-
-/*
-** Return the full pathname of the journal file.
-*/
-const char *sqlite3PagerJournalname(Pager *pPager){
-  return pPager->zJournal;
-}
-
-/*
-** Return true if fsync() calls are disabled for this pager.  Return FALSE
-** if fsync()s are executed normally.
-*/
-int sqlite3PagerNosync(Pager *pPager){
-  return pPager->noSync;
-}
-
-#ifdef SQLITE_HAS_CODEC
-/*
-** Set or retrieve the codec for this pager
-*/
-void sqlite3PagerSetCodec(
-  Pager *pPager,
-  void *(*xCodec)(void*,void*,Pgno,int),
-  void (*xCodecSizeChng)(void*,int,int),
-  void (*xCodecFree)(void*),
-  void *pCodec
-){
-  if( pPager->xCodecFree ) pPager->xCodecFree(pPager->pCodec);
-  pPager->xCodec = pPager->memDb ? 0 : xCodec;
-  pPager->xCodecSizeChng = xCodecSizeChng;
-  pPager->xCodecFree = xCodecFree;
-  pPager->pCodec = pCodec;
-  pagerReportSize(pPager);
-}
-void *sqlite3PagerGetCodec(Pager *pPager){
-  return pPager->pCodec;
-}
-
-/*
-** This function is called by the wal module when writing page content
-** into the log file.
-**
-** This function returns a pointer to a buffer containing the encrypted
-** page content. If a malloc fails, this function may return NULL.
-*/
-void *sqlite3PagerCodec(PgHdr *pPg){
-  void *aData = 0;
-  CODEC2(pPg->pPager, pPg->pData, pPg->pgno, 6, return 0, aData);
-  return aData;
-}
-
-/*
-** Return the current pager state
-*/
-int sqlite3PagerState(Pager *pPager){
-  return pPager->eState;
-}
-#endif /* SQLITE_HAS_CODEC */
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-/*
-** Move the page pPg to location pgno in the file.
-**
-** There must be no references to the page previously located at
-** pgno (which we call pPgOld) though that page is allowed to be
-** in cache.  If the page previously located at pgno is not already
-** in the rollback journal, it is not put there by by this routine.
-**
-** References to the page pPg remain valid. Updating any
-** meta-data associated with pPg (i.e. data stored in the nExtra bytes
-** allocated along with the page) is the responsibility of the caller.
-**
-** A transaction must be active when this routine is called. It used to be
-** required that a statement transaction was not active, but this restriction
-** has been removed (CREATE INDEX needs to move a page when a statement
-** transaction is active).
-**
-** If the fourth argument, isCommit, is non-zero, then this page is being
-** moved as part of a database reorganization just before the transaction 
-** is being committed. In this case, it is guaranteed that the database page 
-** pPg refers to will not be written to again within this transaction.
-**
-** This function may return SQLITE_NOMEM or an IO error code if an error
-** occurs. Otherwise, it returns SQLITE_OK.
-*/
-int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
-  PgHdr *pPgOld;               /* The page being overwritten. */
-  Pgno needSyncPgno = 0;       /* Old value of pPg->pgno, if sync is required */
-  int rc;                      /* Return code */
-  Pgno origPgno;               /* The original page number */
-
-  assert( pPg->nRef>0 );
-  assert( pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-  );
-  assert( assert_pager_state(pPager) );
-
-  /* In order to be able to rollback, an in-memory database must journal
-  ** the page we are moving from.
-  */
-  if( MEMDB ){
-    rc = sqlite3PagerWrite(pPg);
-    if( rc ) return rc;
-  }
-
-  /* If the page being moved is dirty and has not been saved by the latest
-  ** savepoint, then save the current contents of the page into the 
-  ** sub-journal now. This is required to handle the following scenario:
-  **
-  **   BEGIN;
-  **     <journal page X, then modify it in memory>
-  **     SAVEPOINT one;
-  **       <Move page X to location Y>
-  **     ROLLBACK TO one;
-  **
-  ** If page X were not written to the sub-journal here, it would not
-  ** be possible to restore its contents when the "ROLLBACK TO one"
-  ** statement were is processed.
-  **
-  ** subjournalPage() may need to allocate space to store pPg->pgno into
-  ** one or more savepoint bitvecs. This is the reason this function
-  ** may return SQLITE_NOMEM.
-  */
-  if( (pPg->flags & PGHDR_DIRTY)!=0
-   && SQLITE_OK!=(rc = subjournalPageIfRequired(pPg))
-  ){
-    return rc;
-  }
-
-  PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n", 
-      PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno));
-  IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
-
-  /* If the journal needs to be sync()ed before page pPg->pgno can
-  ** be written to, store pPg->pgno in local variable needSyncPgno.
-  **
-  ** If the isCommit flag is set, there is no need to remember that
-  ** the journal needs to be sync()ed before database page pPg->pgno 
-  ** can be written to. The caller has already promised not to write to it.
-  */
-  if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
-    needSyncPgno = pPg->pgno;
-    assert( pPager->journalMode==PAGER_JOURNALMODE_OFF ||
-            pageInJournal(pPager, pPg) || pPg->pgno>pPager->dbOrigSize );
-    assert( pPg->flags&PGHDR_DIRTY );
-  }
-
-  /* If the cache contains a page with page-number pgno, remove it
-  ** from its hash chain. Also, if the PGHDR_NEED_SYNC flag was set for 
-  ** page pgno before the 'move' operation, it needs to be retained 
-  ** for the page moved there.
-  */
-  pPg->flags &= ~PGHDR_NEED_SYNC;
-  pPgOld = sqlite3PagerLookup(pPager, pgno);
-  assert( !pPgOld || pPgOld->nRef==1 );
-  if( pPgOld ){
-    pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);
-    if( MEMDB ){
-      /* Do not discard pages from an in-memory database since we might
-      ** need to rollback later.  Just move the page out of the way. */
-      sqlite3PcacheMove(pPgOld, pPager->dbSize+1);
-    }else{
-      sqlite3PcacheDrop(pPgOld);
-    }
-  }
-
-  origPgno = pPg->pgno;
-  sqlite3PcacheMove(pPg, pgno);
-  sqlite3PcacheMakeDirty(pPg);
-
-  /* For an in-memory database, make sure the original page continues
-  ** to exist, in case the transaction needs to roll back.  Use pPgOld
-  ** as the original page since it has already been allocated.
-  */
-  if( MEMDB ){
-    assert( pPgOld );
-    sqlite3PcacheMove(pPgOld, origPgno);
-    sqlite3PagerUnrefNotNull(pPgOld);
-  }
-
-  if( needSyncPgno ){
-    /* If needSyncPgno is non-zero, then the journal file needs to be 
-    ** sync()ed before any data is written to database file page needSyncPgno.
-    ** Currently, no such page exists in the page-cache and the 
-    ** "is journaled" bitvec flag has been set. This needs to be remedied by
-    ** loading the page into the pager-cache and setting the PGHDR_NEED_SYNC
-    ** flag.
-    **
-    ** If the attempt to load the page into the page-cache fails, (due
-    ** to a malloc() or IO failure), clear the bit in the pInJournal[]
-    ** array. Otherwise, if the page is loaded and written again in
-    ** this transaction, it may be written to the database file before
-    ** it is synced into the journal file. This way, it may end up in
-    ** the journal file twice, but that is not a problem.
-    */
-    PgHdr *pPgHdr;
-    rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr);
-    if( rc!=SQLITE_OK ){
-      if( needSyncPgno<=pPager->dbOrigSize ){
-        assert( pPager->pTmpSpace!=0 );
-        sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace);
-      }
-      return rc;
-    }
-    pPgHdr->flags |= PGHDR_NEED_SYNC;
-    sqlite3PcacheMakeDirty(pPgHdr);
-    sqlite3PagerUnrefNotNull(pPgHdr);
-  }
-
-  return SQLITE_OK;
-}
-#endif
-
-/*
-** The page handle passed as the first argument refers to a dirty page 
-** with a page number other than iNew. This function changes the page's 
-** page number to iNew and sets the value of the PgHdr.flags field to 
-** the value passed as the third parameter.
-*/
-void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){
-  assert( pPg->pgno!=iNew );
-  pPg->flags = flags;
-  sqlite3PcacheMove(pPg, iNew);
-}
-
-/*
-** Return a pointer to the data for the specified page.
-*/
-void *sqlite3PagerGetData(DbPage *pPg){
-  assert( pPg->nRef>0 || pPg->pPager->memDb );
-  return pPg->pData;
-}
-
-/*
-** Return a pointer to the Pager.nExtra bytes of "extra" space 
-** allocated along with the specified page.
-*/
-void *sqlite3PagerGetExtra(DbPage *pPg){
-  return pPg->pExtra;
-}
-
-/*
-** Get/set the locking-mode for this pager. Parameter eMode must be one
-** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or 
-** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
-** the locking-mode is set to the value specified.
-**
-** The returned value is either PAGER_LOCKINGMODE_NORMAL or
-** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
-** locking-mode.
-*/
-int sqlite3PagerLockingMode(Pager *pPager, int eMode){
-  assert( eMode==PAGER_LOCKINGMODE_QUERY
-            || eMode==PAGER_LOCKINGMODE_NORMAL
-            || eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
-  assert( PAGER_LOCKINGMODE_QUERY<0 );
-  assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
-  assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) );
-  if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){
-    pPager->exclusiveMode = (u8)eMode;
-  }
-  return (int)pPager->exclusiveMode;
-}
-
-/*
-** Set the journal-mode for this pager. Parameter eMode must be one of:
-**
-**    PAGER_JOURNALMODE_DELETE
-**    PAGER_JOURNALMODE_TRUNCATE
-**    PAGER_JOURNALMODE_PERSIST
-**    PAGER_JOURNALMODE_OFF
-**    PAGER_JOURNALMODE_MEMORY
-**    PAGER_JOURNALMODE_WAL
-**
-** The journalmode is set to the value specified if the change is allowed.
-** The change may be disallowed for the following reasons:
-**
-**   *  An in-memory database can only have its journal_mode set to _OFF
-**      or _MEMORY.
-**
-**   *  Temporary databases cannot have _WAL journalmode.
-**
-** The returned indicate the current (possibly updated) journal-mode.
-*/
-int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
-  u8 eOld = pPager->journalMode;    /* Prior journalmode */
-
-#ifdef SQLITE_DEBUG
-  /* The print_pager_state() routine is intended to be used by the debugger
-  ** only.  We invoke it once here to suppress a compiler warning. */
-  print_pager_state(pPager);
-#endif
-
-
-  /* The eMode parameter is always valid */
-  assert(      eMode==PAGER_JOURNALMODE_DELETE
-            || eMode==PAGER_JOURNALMODE_TRUNCATE
-            || eMode==PAGER_JOURNALMODE_PERSIST
-            || eMode==PAGER_JOURNALMODE_OFF 
-            || eMode==PAGER_JOURNALMODE_WAL 
-            || eMode==PAGER_JOURNALMODE_MEMORY );
-
-  /* This routine is only called from the OP_JournalMode opcode, and
-  ** the logic there will never allow a temporary file to be changed
-  ** to WAL mode.
-  */
-  assert( pPager->tempFile==0 || eMode!=PAGER_JOURNALMODE_WAL );
-
-  /* Do allow the journalmode of an in-memory database to be set to
-  ** anything other than MEMORY or OFF
-  */
-  if( MEMDB ){
-    assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF );
-    if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){
-      eMode = eOld;
-    }
-  }
-
-  if( eMode!=eOld ){
-
-    /* Change the journal mode. */
-    assert( pPager->eState!=PAGER_ERROR );
-    pPager->journalMode = (u8)eMode;
-
-    /* When transistioning from TRUNCATE or PERSIST to any other journal
-    ** mode except WAL, unless the pager is in locking_mode=exclusive mode,
-    ** delete the journal file.
-    */
-    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
-    assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
-    assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
-    assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
-    assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
-    assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
-
-    assert( isOpen(pPager->fd) || pPager->exclusiveMode );
-    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
-
-      /* In this case we would like to delete the journal file. If it is
-      ** not possible, then that is not a problem. Deleting the journal file
-      ** here is an optimization only.
-      **
-      ** Before deleting the journal file, obtain a RESERVED lock on the
-      ** database file. This ensures that the journal file is not deleted
-      ** while it is in use by some other client.
-      */
-      sqlite3OsClose(pPager->jfd);
-      if( pPager->eLock>=RESERVED_LOCK ){
-        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
-      }else{
-        int rc = SQLITE_OK;
-        int state = pPager->eState;
-        assert( state==PAGER_OPEN || state==PAGER_READER );
-        if( state==PAGER_OPEN ){
-          rc = sqlite3PagerSharedLock(pPager);
-        }
-        if( pPager->eState==PAGER_READER ){
-          assert( rc==SQLITE_OK );
-          rc = pagerLockDb(pPager, RESERVED_LOCK);
-        }
-        if( rc==SQLITE_OK ){
-          sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
-        }
-        if( rc==SQLITE_OK && state==PAGER_READER ){
-          pagerUnlockDb(pPager, SHARED_LOCK);
-        }else if( state==PAGER_OPEN ){
-          pager_unlock(pPager);
-        }
-        assert( state==pPager->eState );
-      }
-    }else if( eMode==PAGER_JOURNALMODE_OFF ){
-      sqlite3OsClose(pPager->jfd);
-    }
-  }
-
-  /* Return the new journal mode */
-  return (int)pPager->journalMode;
-}
-
-/*
-** Return the current journal mode.
-*/
-int sqlite3PagerGetJournalMode(Pager *pPager){
-  return (int)pPager->journalMode;
-}
-
-/*
-** Return TRUE if the pager is in a state where it is OK to change the
-** journalmode.  Journalmode changes can only happen when the database
-** is unmodified.
-*/
-int sqlite3PagerOkToChangeJournalMode(Pager *pPager){
-  assert( assert_pager_state(pPager) );
-  if( pPager->eState>=PAGER_WRITER_CACHEMOD ) return 0;
-  if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0;
-  return 1;
-}
-
-/*
-** Get/set the size-limit used for persistent journal files.
-**
-** Setting the size limit to -1 means no limit is enforced.
-** An attempt to set a limit smaller than -1 is a no-op.
-*/
-i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
-  if( iLimit>=-1 ){
-    pPager->journalSizeLimit = iLimit;
-    sqlite3WalLimit(pPager->pWal, iLimit);
-  }
-  return pPager->journalSizeLimit;
-}
-
-/*
-** Return a pointer to the pPager->pBackup variable. The backup module
-** in backup.c maintains the content of this variable. This module
-** uses it opaquely as an argument to sqlite3BackupRestart() and
-** sqlite3BackupUpdate() only.
-*/
-sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){
-  return &pPager->pBackup;
-}
-
-#ifndef SQLITE_OMIT_VACUUM
-/*
-** Unless this is an in-memory or temporary database, clear the pager cache.
-*/
-void sqlite3PagerClearCache(Pager *pPager){
-  if( !MEMDB && pPager->tempFile==0 ) pager_reset(pPager);
-}
-#endif
-
-#ifndef SQLITE_OMIT_WAL
-/*
-** This function is called when the user invokes "PRAGMA wal_checkpoint",
-** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint()
-** or wal_blocking_checkpoint() API functions.
-**
-** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
-*/
-int sqlite3PagerCheckpoint(Pager *pPager, int eMode, int *pnLog, int *pnCkpt){
-  int rc = SQLITE_OK;
-  if( pPager->pWal ){
-    rc = sqlite3WalCheckpoint(pPager->pWal, eMode,
-        (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler),
-        pPager->pBusyHandlerArg,
-        pPager->ckptSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
-        pnLog, pnCkpt
-    );
-  }
-  return rc;
-}
-
-int sqlite3PagerWalCallback(Pager *pPager){
-  return sqlite3WalCallback(pPager->pWal);
-}
-
-/*
-** Return true if the underlying VFS for the given pager supports the
-** primitives necessary for write-ahead logging.
-*/
-int sqlite3PagerWalSupported(Pager *pPager){
-  const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
-  return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap);
-}
-
-/*
-** Attempt to take an exclusive lock on the database file. If a PENDING lock
-** is obtained instead, immediately release it.
-*/
-static int pagerExclusiveLock(Pager *pPager){
-  int rc;                         /* Return code */
-
-  assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
-  rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
-  if( rc!=SQLITE_OK ){
-    /* If the attempt to grab the exclusive lock failed, release the 
-    ** pending lock that may have been obtained instead.  */
-    pagerUnlockDb(pPager, SHARED_LOCK);
-  }
-
-  return rc;
-}
-
-/*
-** Call sqlite3WalOpen() to open the WAL handle. If the pager is in 
-** exclusive-locking mode when this function is called, take an EXCLUSIVE
-** lock on the database file and use heap-memory to store the wal-index
-** in. Otherwise, use the normal shared-memory.
-*/
-static int pagerOpenWal(Pager *pPager){
-  int rc = SQLITE_OK;
-
-  assert( pPager->pWal==0 && pPager->tempFile==0 );
-  assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
-
-  /* If the pager is already in exclusive-mode, the WAL module will use 
-  ** heap-memory for the wal-index instead of the VFS shared-memory 
-  ** implementation. Take the exclusive lock now, before opening the WAL
-  ** file, to make sure this is safe.
-  */
-  if( pPager->exclusiveMode ){
-    rc = pagerExclusiveLock(pPager);
-  }
-
-  /* Open the connection to the log file. If this operation fails, 
-  ** (e.g. due to malloc() failure), return an error code.
-  */
-  if( rc==SQLITE_OK ){
-    rc = sqlite3WalOpen(pPager->pVfs,
-        pPager->fd, pPager->zWal, pPager->exclusiveMode,
-        pPager->journalSizeLimit, &pPager->pWal
-    );
-  }
-  pagerFixMaplimit(pPager);
-
-  return rc;
-}
-
-
-/*
-** The caller must be holding a SHARED lock on the database file to call
-** this function.
-**
-** If the pager passed as the first argument is open on a real database
-** file (not a temp file or an in-memory database), and the WAL file
-** is not already open, make an attempt to open it now. If successful,
-** return SQLITE_OK. If an error occurs or the VFS used by the pager does 
-** not support the xShmXXX() methods, return an error code. *pbOpen is
-** not modified in either case.
-**
-** If the pager is open on a temp-file (or in-memory database), or if
-** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK
-** without doing anything.
-*/
-int sqlite3PagerOpenWal(
-  Pager *pPager,                  /* Pager object */
-  int *pbOpen                     /* OUT: Set to true if call is a no-op */
-){
-  int rc = SQLITE_OK;             /* Return code */
-
-  assert( assert_pager_state(pPager) );
-  assert( pPager->eState==PAGER_OPEN   || pbOpen );
-  assert( pPager->eState==PAGER_READER || !pbOpen );
-  assert( pbOpen==0 || *pbOpen==0 );
-  assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) );
-
-  if( !pPager->tempFile && !pPager->pWal ){
-    if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;
-
-    /* Close any rollback journal previously open */
-    sqlite3OsClose(pPager->jfd);
-
-    rc = pagerOpenWal(pPager);
-    if( rc==SQLITE_OK ){
-      pPager->journalMode = PAGER_JOURNALMODE_WAL;
-      pPager->eState = PAGER_OPEN;
-    }
-  }else{
-    *pbOpen = 1;
-  }
-
-  return rc;
-}
-
-/*
-** This function is called to close the connection to the log file prior
-** to switching from WAL to rollback mode.
-**
-** Before closing the log file, this function attempts to take an 
-** EXCLUSIVE lock on the database file. If this cannot be obtained, an
-** error (SQLITE_BUSY) is returned and the log connection is not closed.
-** If successful, the EXCLUSIVE lock is not released before returning.
-*/
-int sqlite3PagerCloseWal(Pager *pPager){
-  int rc = SQLITE_OK;
-
-  assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
-
-  /* If the log file is not already open, but does exist in the file-system,
-  ** it may need to be checkpointed before the connection can switch to
-  ** rollback mode. Open it now so this can happen.
-  */
-  if( !pPager->pWal ){
-    int logexists = 0;
-    rc = pagerLockDb(pPager, SHARED_LOCK);
-    if( rc==SQLITE_OK ){
-      rc = sqlite3OsAccess(
-          pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &logexists
-      );
-    }
-    if( rc==SQLITE_OK && logexists ){
-      rc = pagerOpenWal(pPager);
-    }
-  }
-    
-  /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on
-  ** the database file, the log and log-summary files will be deleted.
-  */
-  if( rc==SQLITE_OK && pPager->pWal ){
-    rc = pagerExclusiveLock(pPager);
-    if( rc==SQLITE_OK ){
-      rc = sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags,
-                           pPager->pageSize, (u8*)pPager->pTmpSpace);
-      pPager->pWal = 0;
-      pagerFixMaplimit(pPager);
-    }
-  }
-  return rc;
-}
-
-#endif /* !SQLITE_OMIT_WAL */
-
-#ifdef SQLITE_ENABLE_ZIPVFS
-/*
-** A read-lock must be held on the pager when this function is called. If
-** the pager is in WAL mode and the WAL file currently contains one or more
-** frames, return the size in bytes of the page images stored within the
-** WAL frames. Otherwise, if this is not a WAL database or the WAL file
-** is empty, return 0.
-*/
-int sqlite3PagerWalFramesize(Pager *pPager){
-  assert( pPager->eState>=PAGER_READER );
-  return sqlite3WalFramesize(pPager->pWal);
-}
-#endif
-
-
-#endif /* SQLITE_OMIT_DISKIO */