diff options
Diffstat (limited to 'drivers/staging/batman-adv/bitarray.c')
| -rw-r--r-- | drivers/staging/batman-adv/bitarray.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/drivers/staging/batman-adv/bitarray.c b/drivers/staging/batman-adv/bitarray.c new file mode 100644 index 000000000000..3c67f5f42b2b --- /dev/null +++ b/drivers/staging/batman-adv/bitarray.c @@ -0,0 +1,177 @@ +/* + * Copyright (C) 2006-2009 B.A.T.M.A.N. contributors: + * + * Simon Wunderlich, Marek Lindner + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA + * + */ + +#include "main.h" +#include "bitarray.h" +#include "log.h" + +/* returns true if the corresponding bit in the given seq_bits indicates true + * and curr_seqno is within range of last_seqno */ +uint8_t get_bit_status(TYPE_OF_WORD *seq_bits, uint16_t last_seqno, + uint16_t curr_seqno) +{ + int16_t diff, word_offset, word_num; + + diff = last_seqno - curr_seqno; + if (diff < 0 || diff >= TQ_LOCAL_WINDOW_SIZE) { + return 0; + } else { + /* which word */ + word_num = (last_seqno - curr_seqno) / WORD_BIT_SIZE; + /* which position in the selected word */ + word_offset = (last_seqno - curr_seqno) % WORD_BIT_SIZE; + + if (seq_bits[word_num] & 1 << word_offset) + return 1; + else + return 0; + } +} + +/* turn corresponding bit on, so we can remember that we got the packet */ +void bit_mark(TYPE_OF_WORD *seq_bits, int32_t n) +{ + int32_t word_offset, word_num; + + /* if too old, just drop it */ + if (n < 0 || n >= TQ_LOCAL_WINDOW_SIZE) + return; + + /* which word */ + word_num = n / WORD_BIT_SIZE; + /* which position in the selected word */ + word_offset = n % WORD_BIT_SIZE; + + seq_bits[word_num] |= 1 << word_offset; /* turn the position on */ +} + +/* shift the packet array by n places. */ +void bit_shift(TYPE_OF_WORD *seq_bits, int32_t n) +{ + int32_t word_offset, word_num; + int32_t i; + + if (n <= 0) + return; + + word_offset = n % WORD_BIT_SIZE;/* shift how much inside each word */ + word_num = n / WORD_BIT_SIZE; /* shift over how much (full) words */ + + for (i = NUM_WORDS - 1; i > word_num; i--) { + /* going from old to new, so we don't overwrite the data we copy + * from. + * + * left is high, right is low: FEDC BA98 7654 3210 + * ^^ ^^ + * vvvv + * ^^^^ = from, vvvvv =to, we'd have word_num==1 and + * word_offset==WORD_BIT_SIZE/2 ????? in this example. + * (=24 bits) + * + * our desired output would be: 9876 5432 1000 0000 + * */ + + seq_bits[i] = + (seq_bits[i - word_num] << word_offset) + + /* take the lower port from the left half, shift it left + * to its final position */ + (seq_bits[i - word_num - 1] >> + (WORD_BIT_SIZE-word_offset)); + /* and the upper part of the right half and shift it left to + * it's position */ + /* for our example that would be: word[0] = 9800 + 0076 = + * 9876 */ + } + /* now for our last word, i==word_num, we only have the it's "left" + * half. that's the 1000 word in our example.*/ + + seq_bits[i] = (seq_bits[i - word_num] << word_offset); + + /* pad the rest with 0, if there is anything */ + i--; + + for (; i >= 0; i--) + seq_bits[i] = 0; +} + + +/* receive and process one packet, returns 1 if received seq_num is considered + * new, 0 if old */ +char bit_get_packet(TYPE_OF_WORD *seq_bits, int16_t seq_num_diff, + int8_t set_mark) +{ + int i; + + /* we already got a sequence number higher than this one, so we just + * mark it. this should wrap around the integer just fine */ + if ((seq_num_diff < 0) && (seq_num_diff >= -TQ_LOCAL_WINDOW_SIZE)) { + if (set_mark) + bit_mark(seq_bits, -seq_num_diff); + return 0; + } + + /* it seems we missed a lot of packets or the other host restarted */ + if ((seq_num_diff > TQ_LOCAL_WINDOW_SIZE) || + (seq_num_diff < -TQ_LOCAL_WINDOW_SIZE)) { + + if (seq_num_diff > TQ_LOCAL_WINDOW_SIZE) + debug_log(LOG_TYPE_BATMAN, + "We missed a lot of packets (%i) !\n", + seq_num_diff-1); + + if (-seq_num_diff > TQ_LOCAL_WINDOW_SIZE) + debug_log(LOG_TYPE_BATMAN, + "Other host probably restarted !\n"); + + for (i = 0; i < NUM_WORDS; i++) + seq_bits[i] = 0; + + if (set_mark) + seq_bits[0] = 1; /* we only have the latest packet */ + } else { + bit_shift(seq_bits, seq_num_diff); + + if (set_mark) + bit_mark(seq_bits, 0); + } + + return 1; +} + +/* count the hamming weight, how many good packets did we receive? just count + * the 1's. The inner loop uses the Kernighan algorithm, see + * http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan + */ +int bit_packet_count(TYPE_OF_WORD *seq_bits) +{ + int i, hamming = 0; + TYPE_OF_WORD word; + + for (i = 0; i < NUM_WORDS; i++) { + word = seq_bits[i]; + + while (word) { + word &= word-1; + hamming++; + } + } + return hamming; +} |