/*= -*- 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; }