diff options
Diffstat (limited to 'lib/libsqlite3/src/random.c')
-rw-r--r-- | lib/libsqlite3/src/random.c | 51 |
1 files changed, 14 insertions, 37 deletions
diff --git a/lib/libsqlite3/src/random.c b/lib/libsqlite3/src/random.c index d371e446672..ba71245c9eb 100644 --- a/lib/libsqlite3/src/random.c +++ b/lib/libsqlite3/src/random.c @@ -33,24 +33,11 @@ static SQLITE_WSD struct sqlite3PrngType { } sqlite3Prng; /* -** Get a single 8-bit random value from the RC4 PRNG. The Mutex -** must be held while executing this routine. -** -** Why not just use a library random generator like lrand48() for this? -** Because the OP_NewRowid opcode in the VDBE depends on having a very -** good source of random numbers. The lrand48() library function may -** well be good enough. But maybe not. Or maybe lrand48() has some -** subtle problems on some systems that could cause problems. It is hard -** to know. To minimize the risk of problems due to bad lrand48() -** implementations, SQLite uses this random number generator based -** on RC4, which we know works very well. -** -** (Later): Actually, OP_NewRowid does not depend on a good source of -** randomness any more. But we will leave this code in all the same. +** Return N random bytes. */ -static u8 randomByte(void){ +void sqlite3_randomness(int N, void *pBuf){ unsigned char t; - + unsigned char *zBuf = pBuf; /* The "wsdPrng" macro will resolve to the pseudo-random number generator ** state vector. If writable static data is unsupported on the target, @@ -65,6 +52,10 @@ static u8 randomByte(void){ # define wsdPrng sqlite3Prng #endif +#if SQLITE_THREADSAFE + sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG); + sqlite3_mutex_enter(mutex); +#endif /* Initialize the state of the random number generator once, ** the first time this routine is called. The seed value does @@ -93,28 +84,14 @@ static u8 randomByte(void){ wsdPrng.isInit = 1; } - /* Generate and return single random byte - */ - wsdPrng.i++; - t = wsdPrng.s[wsdPrng.i]; - wsdPrng.j += t; - wsdPrng.s[wsdPrng.i] = wsdPrng.s[wsdPrng.j]; - wsdPrng.s[wsdPrng.j] = t; - t += wsdPrng.s[wsdPrng.i]; - return wsdPrng.s[t]; -} - -/* -** Return N random bytes. -*/ -void sqlite3_randomness(int N, void *pBuf){ - unsigned char *zBuf = pBuf; -#if SQLITE_THREADSAFE - sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG); -#endif - sqlite3_mutex_enter(mutex); while( N-- ){ - *(zBuf++) = randomByte(); + wsdPrng.i++; + t = wsdPrng.s[wsdPrng.i]; + wsdPrng.j += t; + wsdPrng.s[wsdPrng.i] = wsdPrng.s[wsdPrng.j]; + wsdPrng.s[wsdPrng.j] = t; + t += wsdPrng.s[wsdPrng.i]; + *(zBuf++) = wsdPrng.s[t]; } sqlite3_mutex_leave(mutex); } |