librsync  2.3.2
sumset.c
1/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*-
2 *
3 * librsync -- library for network deltas
4 *
5 * Copyright (C) 1999, 2000, 2001 by Martin Pool <mbp@sourcefrog.net>
6 * Copyright (C) 1999 by Andrew Tridgell
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU Lesser General Public License as published by
10 * the Free Software Foundation; either version 2.1 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 */
22
23#include "config.h"
24#include <assert.h>
25#include <stdlib.h>
26#include <string.h>
27#include "librsync.h"
28#include "sumset.h"
29#include "trace.h"
30#include "util.h"
31
32static void rs_block_sig_init(rs_block_sig_t *sig, rs_weak_sum_t weak_sum,
33 rs_strong_sum_t *strong_sum, int strong_len)
34{
35 sig->weak_sum = weak_sum;
36 if (strong_sum)
37 memcpy(sig->strong_sum, strong_sum, (size_t)strong_len);
38}
39
40static inline unsigned rs_block_sig_hash(const rs_block_sig_t *sig)
41{
42 return (unsigned)sig->weak_sum;
43}
44
45typedef struct rs_block_match {
46 rs_block_sig_t block_sig;
47 rs_signature_t *signature;
48 const void *buf;
49 size_t len;
51
52static void rs_block_match_init(rs_block_match_t *match, rs_signature_t *sig,
53 rs_weak_sum_t weak_sum,
54 rs_strong_sum_t *strong_sum, const void *buf,
55 size_t len)
56{
57 rs_block_sig_init(&match->block_sig, weak_sum, strong_sum,
58 sig->strong_sum_len);
59 match->signature = sig;
60 match->buf = buf;
61 match->len = len;
62}
63
64static inline int rs_block_match_cmp(rs_block_match_t *match,
65 const rs_block_sig_t *block_sig)
66{
67 /* If buf is not NULL, the strong sum is yet to be calculated. */
68 if (match->buf) {
69#ifndef HASHTABLE_NSTATS
70 match->signature->calc_strong_count++;
71#endif
72 rs_signature_calc_strong_sum(match->signature, match->buf, match->len,
73 &(match->block_sig.strong_sum));
74 match->buf = NULL;
75 }
76 return memcmp(&match->block_sig.strong_sum, &block_sig->strong_sum,
77 (size_t)match->signature->strong_sum_len);
78}
79
80/* Disable mix32() in the hashtable because RabinKarp doesn't need it. We
81 manually apply mix32() to rollsums before using them in the hashtable. */
82#define HASHTABLE_NMIX32
83/* Instantiate hashtable for rs_block_sig and rs_block_match. */
84#define ENTRY rs_block_sig
85#define MATCH rs_block_match
86#define NAME hashtable
87#include "hashtable.h"
88
89/* Get the size of a packed rs_block_sig_t. */
90static inline size_t rs_block_sig_size(const rs_signature_t *sig)
91{
92 /* Round up to multiple of sizeof(weak_sum) to align memory correctly. */
93 const size_t mask = sizeof(rs_weak_sum_t)- 1;
94 return (offsetof(rs_block_sig_t, strong_sum) +
95 (((size_t)sig->strong_sum_len + mask) & ~mask));
96}
97
98/* Get the pointer to the block_sig_t from a block index. */
99static inline rs_block_sig_t *rs_block_sig_ptr(const rs_signature_t *sig,
100 int block_idx)
101{
102 return (rs_block_sig_t *)((char *)sig->block_sigs +
103 block_idx * rs_block_sig_size(sig));
104}
105
106/* Get the index of a block from a block_sig_t pointer. */
107static inline int rs_block_sig_idx(const rs_signature_t *sig,
108 rs_block_sig_t *block_sig)
109{
110 return (int)(((char *)block_sig -
111 (char *)sig->block_sigs) / rs_block_sig_size(sig));
112}
113
114rs_result rs_sig_args(rs_long_t old_fsize, rs_magic_number * magic,
115 size_t *block_len, size_t *strong_len)
116{
117 size_t rec_block_len; /* the recomended block_len for the given
118 old_fsize. */
119 size_t min_strong_len; /* the minimum strong_len for the given
120 old_fsize and block_len. */
121 size_t max_strong_len; /* the maximum strong_len for the given magic. */
122
123 /* Check and set default arguments. */
124 *magic = *magic ? *magic : RS_RK_BLAKE2_SIG_MAGIC;
125 switch (*magic) {
128 max_strong_len = RS_BLAKE2_SUM_LENGTH;
129 break;
130 case RS_MD4_SIG_MAGIC:
132 max_strong_len = RS_MD4_SUM_LENGTH;
133 break;
134 default:
135 rs_error("invalid magic %#x", *magic);
136 return RS_BAD_MAGIC;
137 }
138 /* The recommended block_len is sqrt(old_fsize) with a 256 min size rounded
139 down to a multiple of the 128 byte blake2b blocksize to give a
140 reasonable compromise between signature size, delta size, and
141 performance. If the old_fsize is unknown, we use the default. */
142 if (old_fsize < 0) {
143 rec_block_len = RS_DEFAULT_BLOCK_LEN;
144 } else {
145 rec_block_len =
146 old_fsize <= 256 * 256 ? 256 : rs_long_sqrt(old_fsize) & ~127;
147 }
148 if (*block_len == 0)
149 *block_len = rec_block_len;
150 /* The recommended strong_len assumes the worst case new_fsize = old_fsize
151 + 16MB with no matches. This results in comparing a block at every byte
152 offset against all the blocks in the signature, or new_fsize*block_num
153 comparisons. With N bits in the blocksig, there is a 1/2^N chance per
154 comparison of a hash colision. So with 2^N attempts there would be a
155 fair chance of having a collision. So we want to round up to the next
156 byte, add an extra 2 bytes (16 bits) in the strongsum, and assume the
157 weaksum is worth another 16 bits, for at least 32 bits extra, giving a
158 worst case 1/2^32 chance of having a hash collision per delta. If
159 old_fsize is unknown we use a conservative default. */
160 if (old_fsize < 0) {
161 min_strong_len = RS_DEFAULT_MIN_STRONG_LEN;
162 } else {
163 min_strong_len =
164 2 + (rs_long_ln2(old_fsize + ((rs_long_t)1 << 24)) +
165 rs_long_ln2(old_fsize / *block_len + 1) + 7) / 8;
166 }
167 if (*strong_len == 0)
168 *strong_len = max_strong_len;
169 else if (*strong_len == -1)
170 *strong_len = min_strong_len;
171 else if (old_fsize >= 0 && *strong_len < min_strong_len) {
172 rs_warn("strong_len=" FMT_SIZE " smaller than recommended minimum "
173 FMT_SIZE " for old_fsize=" FMT_LONG " with block_len=" FMT_SIZE,
174 *strong_len, min_strong_len, old_fsize, *block_len);
175 } else if (*strong_len > max_strong_len) {
176 rs_error("invalid strong_len=" FMT_SIZE " for magic=%#x", *strong_len,
177 (int)*magic);
178 return RS_PARAM_ERROR;
179 }
180 rs_sig_args_check(*magic, *block_len, *strong_len);
181 return RS_DONE;
182}
183
184rs_result rs_signature_init(rs_signature_t *sig, rs_magic_number magic,
185 size_t block_len, size_t strong_len,
186 rs_long_t sig_fsize)
187{
188 rs_result result;
189
190 /* Check and set default arguments, using old_fsize=-1 for unknown. */
191 if ((result = rs_sig_args(-1, &magic, &block_len, &strong_len)) != RS_DONE)
192 return result;
193 /* Set attributes from args. */
194 sig->magic = magic;
195 sig->block_len = (int)block_len;
196 sig->strong_sum_len = (int)strong_len;
197 sig->count = 0;
198 /* Calculate the number of blocks if we have the signature file size. */
199 /* Magic+header is 12 bytes, each block thereafter is 4 bytes
200 weak_sum+strong_sum_len bytes */
201 sig->size = (int)(sig_fsize < 12 ? 0 : (sig_fsize - 12) / (4 + strong_len));
202 if (sig->size)
203 sig->block_sigs =
204 rs_alloc(sig->size * rs_block_sig_size(sig),
205 "signature->block_sigs");
206 else
207 sig->block_sigs = NULL;
208 sig->hashtable = NULL;
209#ifndef HASHTABLE_NSTATS
210 sig->calc_strong_count = 0;
211#endif
212 rs_signature_check(sig);
213 return RS_DONE;
214}
215
216void rs_signature_done(rs_signature_t *sig)
217{
218 hashtable_free(sig->hashtable);
219 free(sig->block_sigs);
220 rs_bzero(sig, sizeof(*sig));
221}
222
223rs_block_sig_t *rs_signature_add_block(rs_signature_t *sig,
224 rs_weak_sum_t weak_sum,
225 rs_strong_sum_t *strong_sum)
226{
227 rs_signature_check(sig);
228 /* Apply mix32() to rollsum weaksums to improve their distribution. */
229 if (rs_signature_weaksum_kind(sig) == RS_ROLLSUM)
230 weak_sum = mix32(weak_sum);
231 /* If block_sigs is full, allocate more space. */
232 if (sig->count == sig->size) {
233 sig->size = sig->size ? sig->size * 2 : 16;
234 sig->block_sigs =
235 rs_realloc(sig->block_sigs, sig->size * rs_block_sig_size(sig),
236 "signature->block_sigs");
237 }
238 rs_block_sig_t *b = rs_block_sig_ptr(sig, sig->count++);
239 rs_block_sig_init(b, weak_sum, strong_sum, sig->strong_sum_len);
240 return b;
241}
242
243rs_long_t rs_signature_find_match(rs_signature_t *sig, rs_weak_sum_t weak_sum,
244 void const *buf, size_t len)
245{
248
249 rs_signature_check(sig);
250 rs_block_match_init(&m, sig, weak_sum, NULL, buf, len);
251 if ((b = hashtable_find(sig->hashtable, &m))) {
252 return (rs_long_t)rs_block_sig_idx(sig, b) * sig->block_len;
253 }
254 return -1;
255}
256
258{
259#ifndef HASHTABLE_NSTATS
260 hashtable_t *t = sig->hashtable;
261
262 rs_log(RS_LOG_INFO | RS_LOG_NONAME,
263 "match statistics: signature[%ld searches, %ld (%.3f%%) matches, "
264 "%ld (%.3fx) weak sum compares, %ld (%.3f%%) strong sum compares, "
265 "%ld (%.3f%%) strong sum calcs]", t->find_count, t->match_count,
266 100.0 * (double)t->match_count / (double)t->find_count,
267 t->hashcmp_count, (double)t->hashcmp_count / (double)t->find_count,
269 100.0 * (double)t->entrycmp_count / (double)t->find_count,
271 100.0 * (double)sig->calc_strong_count / (double)t->find_count);
272#endif
273}
274
276{
279 int i;
280
281 rs_signature_check(sig);
282 sig->hashtable = hashtable_new(sig->count);
283 if (!sig->hashtable)
284 return RS_MEM_ERROR;
285 for (i = 0; i < sig->count; i++) {
286 b = rs_block_sig_ptr(sig, i);
287 rs_block_match_init(&m, sig, b->weak_sum, &b->strong_sum, NULL, 0);
288 if (!hashtable_find(sig->hashtable, &m))
289 hashtable_add(sig->hashtable, b);
290 }
291 hashtable_stats_init(sig->hashtable);
292 return RS_DONE;
293}
294
296{
297 rs_signature_done(psums);
298 free(psums);
299}
300
302{
303 int i;
305 char strong_hex[RS_MAX_STRONG_SUM_LENGTH * 3];
306
307 rs_log(RS_LOG_INFO | RS_LOG_NONAME,
308 "sumset info: magic=%#x, block_len=%d, block_num=%d", sums->magic,
309 sums->block_len, sums->count);
310
311 for (i = 0; i < sums->count; i++) {
312 b = rs_block_sig_ptr(sums, i);
313 rs_hexify(strong_hex, b->strong_sum, sums->strong_sum_len);
314 rs_log(RS_LOG_INFO | RS_LOG_NONAME,
315 "sum %6d: weak=" FMT_WEAKSUM ", strong=%s", i, b->weak_sum,
316 strong_hex);
317 }
318}
A generic open addressing hashtable.
static unsigned mix32(unsigned h)
MurmurHash3 finalization mix function.
Definition: hashtable.h:172
Public header for librsync.
LIBRSYNC_EXPORT rs_result rs_build_hash_table(rs_signature_t *sums)
Call this after loading a signature to index it.
Definition: sumset.c:275
LIBRSYNC_EXPORT void rs_signature_log_stats(rs_signature_t const *sig)
Log the rs_signature_delta match stats.
Definition: sumset.c:257
LIBRSYNC_EXPORT rs_result rs_sig_args(rs_long_t old_fsize, rs_magic_number *magic, size_t *block_len, size_t *strong_len)
Get or check signature arguments for a given file size.
Definition: sumset.c:114
LIBRSYNC_EXPORT void rs_free_sumset(rs_signature_t *)
Deep deallocation of checksums.
Definition: sumset.c:295
rs_result
Return codes from nonblocking rsync operations.
Definition: librsync.h:180
@ RS_MEM_ERROR
Out of memory.
Definition: librsync.h:189
@ RS_DONE
Completed successfully.
Definition: librsync.h:181
@ RS_PARAM_ERROR
Bad value passed in to library, probably an application bug.
Definition: librsync.h:200
@ RS_BAD_MAGIC
Bad magic number at start of stream.
Definition: librsync.h:193
#define RS_DEFAULT_BLOCK_LEN
Default block length, if not determined by any other factors.
Definition: librsync.h:361
@ RS_LOG_INFO
Informational.
Definition: librsync.h:125
rs_magic_number
A uint32 magic number, emitted in bigendian/network order at the start of librsync files.
Definition: librsync.h:65
@ RS_BLAKE2_SIG_MAGIC
A signature file using the BLAKE2 hash.
Definition: librsync.h:89
@ RS_MD4_SIG_MAGIC
A signature file with MD4 signatures.
Definition: librsync.h:82
@ RS_RK_BLAKE2_SIG_MAGIC
A signature file with RabinKarp rollsum and BLAKE2 hash.
Definition: librsync.h:109
@ RS_RK_MD4_SIG_MAGIC
A signature file with RabinKarp rollsum and MD4 hash.
Definition: librsync.h:99
#define RS_DEFAULT_MIN_STRONG_LEN
Default minimum strong sum length, if the filesize is unknown.
Definition: librsync.h:367
LIBRSYNC_EXPORT void rs_sumset_dump(rs_signature_t const *)
Dump signatures to the log.
Definition: sumset.c:301
LIBRSYNC_EXPORT void rs_hexify(char *to_buf, void const *from_buf, int from_len)
Convert from_len bytes at from_buf into a hex representation in to_buf, which must be twice as long p...
Definition: hex.c:23
The hashtable type.
Definition: hashtable.h:130
long find_count
The count of finds tried.
Definition: hashtable.h:139
long match_count
The count of matches found.
Definition: hashtable.h:140
long entrycmp_count
The count of entry compares done.
Definition: hashtable.h:142
long hashcmp_count
The count of hash compares done.
Definition: hashtable.h:141
Signature of a single block.
Definition: sumset.h:28
rs_strong_sum_t strong_sum
Block's strong checksum.
Definition: sumset.h:30
rs_weak_sum_t weak_sum
Block's weak checksum.
Definition: sumset.h:29
Signature of a whole file.
Definition: sumset.h:37
int count
Total number of blocks.
Definition: sumset.h:41
int size
Total number of blocks allocated.
Definition: sumset.h:42
int magic
The signature magic value.
Definition: sumset.h:38
hashtable_t * hashtable
The hashtable for finding matches.
Definition: sumset.h:44
int block_len
The block length.
Definition: sumset.h:39
void * block_sigs
The packed block_sigs for all blocks.
Definition: sumset.h:43
long calc_strong_count
The count of strongsum calcs done.
Definition: sumset.h:47
int strong_sum_len
The block strong sum length.
Definition: sumset.h:40
logging functions.
@ RS_LOG_NONAME
Don't show function name in message.
Definition: trace.h:83