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 
32 static 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 
40 static inline unsigned rs_block_sig_hash(const rs_block_sig_t *sig)
41 {
42  return (unsigned)sig->weak_sum;
43 }
44 
45 typedef 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 
52 static 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 
64 static 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. */
90 static 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. */
99 static 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. */
107 static 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 
114 rs_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) {
126  case RS_BLAKE2_SIG_MAGIC:
128  max_strong_len = RS_BLAKE2_SUM_LENGTH;
129  break;
130  case RS_MD4_SIG_MAGIC:
131  case RS_RK_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 
184 rs_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 
216 void 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 
223 rs_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 
243 rs_long_t rs_signature_find_match(rs_signature_t *sig, rs_weak_sum_t weak_sum,
244  void const *buf, size_t len)
245 {
247  rs_block_sig_t *b;
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,
268  t->entrycmp_count,
269  100.0 * (double)t->entrycmp_count / (double)t->find_count,
270  sig->calc_strong_count,
271  100.0 * (double)sig->calc_strong_count / (double)t->find_count);
272 #endif
273 }
274 
276 {
278  rs_block_sig_t *b;
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;
304  rs_block_sig_t *b;
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