| -rw-r--r-- | rsync/search.c | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/rsync/search.c b/rsync/search.c new file mode 100644 index 0000000..3e0c5e2 --- a/dev/null +++ b/rsync/search.c @@ -0,0 +1,162 @@ +/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*- + * + * librsync -- the library for network deltas + * $Id$ + * + * Copyright (C) 1999, 2000, 2001 by Martin Pool <mbp@samba.org> + * Copyright (C) 1999 by Andrew Tridgell + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation; either version 2.1 of the License, or + * (at your option) any later version. + * + * 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 Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +/* + * This file contains code for searching the sumset for matching + * values. + */ + +/* + * TODO: The common case is that the next block in both streams + * match. Can we make that a bit faster at all? We'd need to perhaps + * add a link forward between blocks in the sum_struct corresponding + * to the order they're found in the input; then before doing a search + * we can just check that pointer. + */ + +#include <config_rsync.h> + +#include <string.h> +#include <assert.h> +#include <stdlib.h> +#include <stdio.h> + +#include "rsync.h" +#include "trace.h" +#include "util.h" +#include "sumset.h" +#include "search.h" +#include "checksum.h" + + +#define TABLESIZE (1<<16) +#define NULL_TAG (-1) + + +#define gettag2(s1,s2) (((s1) + (s2)) & 0xFFFF) +#define gettag(sum) gettag2((sum)&0xFFFF,(sum)>>16) + + +static int +rs_compare_targets(rs_target_t const *t1, rs_target_t const *t2) +{ + return ((int) t1->t - (int) t2->t); +} + + +rs_result +rs_build_hash_table(rs_signature_t * sums) +{ + int i; + + sums->tag_table = calloc(TABLESIZE, sizeof sums->tag_table[0]); + if (!sums->tag_table) + return RS_MEM_ERROR; + + if (sums->count > 0) { + sums->targets = calloc(sums->count, sizeof(rs_target_t)); + if (!sums->targets) + return RS_MEM_ERROR; + + for (i = 0; i < sums->count; i++) { + sums->targets[i].i = i; + sums->targets[i].t = gettag(sums->block_sigs[i].weak_sum); + } + + /* FIXME: Perhaps if this operating system has comparison_fn_t + * like GNU, then use it in the cast. But really does anyone + * care? */ + qsort(sums->targets, sums->count, + sizeof(sums->targets[0]), + (int (*)(const void *, const void *)) rs_compare_targets); + } + + for (i = 0; i < TABLESIZE; i++) + sums->tag_table[i] = NULL_TAG; + + for (i = sums->count - 1; i >= 0; i--) { + sums->tag_table[sums->targets[i].t] = i; + } + + rs_trace("done"); + return RS_DONE; +} + + + +/* + * See if there is a match for the specified block INBUF..BLOCK_LEN in + * the checksum set, using precalculated WEAK_SUM. + * + * If we don't find a match on the weak checksum, then we just give + * up. If we do find a weak match, then we proceed to calculate the + * strong checksum for the current block, and see if it will match + * anything. + */ +int +rs_search_for_block(rs_weak_sum_t weak_sum, + char const *inbuf, size_t block_len, + rs_signature_t const *sig, rs_stats_t * stats, + rs_long_t * match_where) +{ + int hash_tag = gettag(weak_sum); + int j = sig->tag_table[hash_tag]; + rs_strong_sum_t strong_sum; + int got_strong = 0; + + if (j == NULL_TAG) { + return 0; + } + + for (; j < sig->count && sig->targets[j].t == hash_tag; j++) { + int i = sig->targets[j].i; + int token; + + if (weak_sum != sig->block_sigs[i].weak_sum) + continue; + + token = sig->block_sigs[i].i; + + rs_trace("found weak match for %08x in token %d", weak_sum, token); + + if (!got_strong) { + rs_calc_strong_sum(inbuf, block_len, &strong_sum); + got_strong = 1; + } + + /* FIXME: Use correct dynamic sum length! */ + if (memcmp(strong_sum, sig->block_sigs[i].strong_sum, + sig->strong_sum_len) == 0) { + /* XXX: This is a remnant of rsync: token number 1 is the + * block at offset 0. It would be good to clear this + * up. */ + *match_where = (token - 1) * sig->block_len; + return 1; + } else { + rs_trace("this was a false positive, the strong sig doesn't match"); + stats->false_matches++; + } + } + + return 0; +} |