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/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*-
*
* librsync -- the library for network deltas
*
* Copyright (C) 1999, 2000, 2001, 2014 by Martin Pool <mbp@sourcefrog.net>
* 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.h>
#include <string.h>
#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include "librsync.h"
#include "trace.h"
#include "util.h"
#include "sumset.h"
#include "search.h"
#include "checksum.h"
#define TABLE_SIZE (1<<16)
#define NULL_TAG (-1)
#define gettag2(s1,s2) (((s1) + (s2)) & 0xFFFF)
#define gettag(sum) gettag2((sum)&0xFFFF,(sum)>>16)
static void swap(rs_target_t *t1, rs_target_t *t2) {
unsigned short ts = t1->t;
t1->t = t2->t;
t2->t = ts;
int ti = t1->i;
t1->i = t2->i;
t2->i = ti;
}
int rs_compare_targets(rs_target_t const *t1, rs_target_t const *t2, rs_signature_t * sums) {
int v = (int) t1->t - (int) t2->t;
if (v != 0)
return v;
rs_weak_sum_t w1 = sums->block_sigs[t1->i].weak_sum;
rs_weak_sum_t w2 = sums->block_sigs[t2->i].weak_sum;
v = (w1 > w2) - (w1 < w2);
if (v != 0)
return v;
return memcmp(sums->block_sigs[t1->i].strong_sum,
sums->block_sigs[t2->i].strong_sum,
sums->strong_sum_len);
}
static int heap_sort(rs_signature_t * sums) {
unsigned int i, j, c, n, k, p;
for (i = 1; i < sums->count; ++i) {
for (j = i; j > 0;) {
p = (j - 1) >> 1;
if (rs_compare_targets(&sums->targets[j], &sums->targets[p], sums) > 0)
swap(&sums->targets[j], &sums->targets[p]);
else
break;
j = p;
}
}
for (n = sums->count - 1; n > 0;) {
swap(&sums->targets[0], &sums->targets[n]);
--n;
for (i = 0; ((i << 1) + 1) <= n;) {
k = (i << 1) + 1;
if ((k + 1 <= n) && (rs_compare_targets(&sums->targets[k], &sums->targets[k + 1], sums) < 0))
k = k + 1;
if (rs_compare_targets(&sums->targets[k], &sums->targets[i], sums) > 0)
swap(&sums->targets[k], &sums->targets[i]);
else
break;
i = k;
}
}
}
rs_result
rs_build_hash_table(rs_signature_t * sums)
{
int i;
sums->tag_table = calloc(TABLE_SIZE, 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) {
free(sums->tag_table);
sums->tag_table = NULL;
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);
}
heap_sort(sums);
}
for (i = 0; i < TABLE_SIZE; i++) {
sums->tag_table[i].l = NULL_TAG;
sums->tag_table[i].r = NULL_TAG;
}
for (i = sums->count - 1; i >= 0; i--) {
sums->tag_table[sums->targets[i].t].l = i;
}
for (i = 0; i < sums->count; i++) {
sums->tag_table[sums->targets[i].t].r = i;
}
rs_trace("rs_build_hash_table 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,
const rs_byte_t *inbuf,
size_t block_len,
rs_signature_t const *sig, rs_stats_t * stats,
rs_long_t * match_where)
{
rs_strong_sum_t strong_sum;
int got_strong = 0;
int hash_tag = gettag(weak_sum);
rs_tag_table_entry_t *bucket = &(sig->tag_table[hash_tag]);
int l = bucket->l;
int r = bucket->r + 1;
int v = 1;
if (l == NULL_TAG)
return 0;
while (l < r) {
int m = (l + r) >> 1;
int i = sig->targets[m].i;
rs_block_sig_t *b = &(sig->block_sigs[i]);
v = (weak_sum > b->weak_sum) - (weak_sum < b->weak_sum); // v < 0 - weak_sum < b->weak_sum
// v == 0 - weak_sum == b->weak_sum
// v > 0 - weak_sum > b->weak_sum
if (v == 0) {
if (!got_strong) {
if(sig->magic == RS_BLAKE2_SIG_MAGIC) {
rs_calc_blake2_sum(inbuf, block_len, &strong_sum);
} else if (sig->magic == RS_MD4_SIG_MAGIC) {
rs_calc_md4_sum(inbuf, block_len, &strong_sum);
} else {
rs_error("Unknown signature algorithm - this is a BUG");
return 0; /* FIXME: Is this the best way to handle this? */
}
got_strong = 1;
}
v = memcmp(strong_sum, b->strong_sum, sig->strong_sum_len);
if (v == 0) {
l = m;
r = m;
break;
}
}
if (v > 0)
l = m + 1;
else
r = m;
}
if (l == r) {
int i = sig->targets[l].i;
rs_block_sig_t *b = &(sig->block_sigs[i]);
if (weak_sum != b->weak_sum)
return 0;
if (!got_strong) {
if(sig->magic == RS_BLAKE2_SIG_MAGIC) {
rs_calc_blake2_sum(inbuf, block_len, &strong_sum);
} else if (sig->magic == RS_MD4_SIG_MAGIC) {
rs_calc_md4_sum(inbuf, block_len, &strong_sum);
} else {
rs_error("Unknown signature algorithm - this is a BUG");
return 0; /* FIXME: Is this the best way to handle this? */
}
got_strong = 1;
}
v = memcmp(strong_sum, b->strong_sum, sig->strong_sum_len);
int token = b->i;
*match_where = (rs_long_t)(token - 1) * sig->block_len;
}
return !v;
}
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