File: match.c

package info (click to toggle)
rsync 3.1.3-6
  • links: PTS, VCS
  • area: main
  • in suites: buster, sid
  • size: 3,888 kB
  • sloc: ansic: 40,820; sh: 5,508; perl: 1,932; makefile: 326; python: 83
file content (449 lines) | stat: -rw-r--r-- 12,712 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
/*
 * Block matching used by the file-transfer code.
 *
 * Copyright (C) 1996 Andrew Tridgell
 * Copyright (C) 1996 Paul Mackerras
 * Copyright (C) 2003-2018 Wayne Davison
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, visit the http://fsf.org website.
 */

#include "rsync.h"
#include "inums.h"

extern int checksum_seed;
extern int append_mode;
extern int xfersum_type;

int updating_basis_file;
char sender_file_sum[MAX_DIGEST_LEN];

static int false_alarms;
static int hash_hits;
static int matches;
static int64 data_transfer;

static int total_false_alarms;
static int total_hash_hits;
static int total_matches;

extern struct stats stats;

#define TRADITIONAL_TABLESIZE (1<<16)

static uint32 tablesize;
static int32 *hash_table;

#define SUM2HASH2(s1,s2) (((s1) + (s2)) & 0xFFFF)
#define SUM2HASH(sum) SUM2HASH2((sum)&0xFFFF,(sum)>>16)

#define BIG_SUM2HASH(sum) ((sum)%tablesize)

static void build_hash_table(struct sum_struct *s)
{
	static uint32 alloc_size;
	int32 i;

	/* Dynamically calculate the hash table size so that the hash load
	 * for big files is about 80%.  A number greater than the traditional
	 * size must be odd or s2 will not be able to span the entire set. */
	tablesize = (uint32)(s->count/8) * 10 + 11;
	if (tablesize < TRADITIONAL_TABLESIZE)
		tablesize = TRADITIONAL_TABLESIZE;
	if (tablesize > alloc_size || tablesize < alloc_size - 16*1024) {
		if (hash_table)
			free(hash_table);
		hash_table = new_array(int32, tablesize);
		if (!hash_table)
			out_of_memory("build_hash_table");
		alloc_size = tablesize;
	}

	memset(hash_table, 0xFF, tablesize * sizeof hash_table[0]);

	if (tablesize == TRADITIONAL_TABLESIZE) {
		for (i = 0; i < s->count; i++) {
			uint32 t = SUM2HASH(s->sums[i].sum1);
			s->sums[i].chain = hash_table[t];
			hash_table[t] = i;
		}
	} else {
		for (i = 0; i < s->count; i++) {
			uint32 t = BIG_SUM2HASH(s->sums[i].sum1);
			s->sums[i].chain = hash_table[t];
			hash_table[t] = i;
		}
	}
}


static OFF_T last_match;


/* Transmit a literal and/or match token.
 *
 * This delightfully-named function is called either when we find a
 * match and need to transmit all the unmatched data leading up to it,
 * or when we get bored of accumulating literal data and just need to
 * transmit it.  As a result of this second case, it is called even if
 * we have not matched at all!
 *
 * If i >= 0, the number of a matched token.  If < 0, indicates we have
 * only literal data.  A -1 will send a 0-token-int too, and a -2 sends
 * only literal data, w/o any token-int. */
static void matched(int f, struct sum_struct *s, struct map_struct *buf,
		    OFF_T offset, int32 i)
{
	int32 n = (int32)(offset - last_match); /* max value: block_size (int32) */
	int32 j;

	if (DEBUG_GTE(DELTASUM, 2) && i >= 0) {
		rprintf(FINFO,
			"match at %s last_match=%s j=%d len=%ld n=%ld\n",
			big_num(offset), big_num(last_match), i,
			(long)s->sums[i].len, (long)n);
	}

	send_token(f, i, buf, last_match, n, i < 0 ? 0 : s->sums[i].len);
	data_transfer += n;

	if (i >= 0) {
		stats.matched_data += s->sums[i].len;
		n += s->sums[i].len;
	}

	for (j = 0; j < n; j += CHUNK_SIZE) {
		int32 n1 = MIN(CHUNK_SIZE, n - j);
		sum_update(map_ptr(buf, last_match + j, n1), n1);
	}

	if (i >= 0)
		last_match = offset + s->sums[i].len;
	else
		last_match = offset;

	if (buf && INFO_GTE(PROGRESS, 1))
		show_progress(last_match, buf->file_size);
}


static void hash_search(int f,struct sum_struct *s,
			struct map_struct *buf, OFF_T len)
{
	OFF_T offset, aligned_offset, end;
	int32 k, want_i, aligned_i, backup;
	char sum2[SUM_LENGTH];
	uint32 s1, s2, sum;
	int more;
	schar *map;

	/* want_i is used to encourage adjacent matches, allowing the RLL
	 * coding of the output to work more efficiently. */
	want_i = 0;

	if (DEBUG_GTE(DELTASUM, 2)) {
		rprintf(FINFO, "hash search b=%ld len=%s\n",
			(long)s->blength, big_num(len));
	}

	k = (int32)MIN(len, (OFF_T)s->blength);

	map = (schar *)map_ptr(buf, 0, k);

	sum = get_checksum1((char *)map, k);
	s1 = sum & 0xFFFF;
	s2 = sum >> 16;
	if (DEBUG_GTE(DELTASUM, 3))
		rprintf(FINFO, "sum=%.8x k=%ld\n", sum, (long)k);

	offset = aligned_offset = aligned_i = 0;

	end = len + 1 - s->sums[s->count-1].len;

	if (DEBUG_GTE(DELTASUM, 3)) {
		rprintf(FINFO, "hash search s->blength=%ld len=%s count=%s\n",
			(long)s->blength, big_num(len), big_num(s->count));
	}

	do {
		int done_csum2 = 0;
		uint32 hash_entry;
		int32 i, *prev;

		if (DEBUG_GTE(DELTASUM, 4)) {
			rprintf(FINFO, "offset=%s sum=%04x%04x\n",
				big_num(offset), s2 & 0xFFFF, s1 & 0xFFFF);
		}

		if (tablesize == TRADITIONAL_TABLESIZE) {
			hash_entry = SUM2HASH2(s1,s2);
			if ((i = hash_table[hash_entry]) < 0)
				goto null_hash;
			sum = (s1 & 0xffff) | (s2 << 16);
		} else {
			sum = (s1 & 0xffff) | (s2 << 16);
			hash_entry = BIG_SUM2HASH(sum);
			if ((i = hash_table[hash_entry]) < 0)
				goto null_hash;
		}
		prev = &hash_table[hash_entry];

		hash_hits++;
		do {
			int32 l;

			/* When updating in-place, the chunk's offset must be
			 * either >= our offset or identical data at that offset.
			 * Remove any bypassed entries that we can never use. */
			if (updating_basis_file && s->sums[i].offset < offset
			    && !(s->sums[i].flags & SUMFLG_SAME_OFFSET)) {
				*prev = s->sums[i].chain;
				continue;
			}
			prev = &s->sums[i].chain;

			if (sum != s->sums[i].sum1)
				continue;

			/* also make sure the two blocks are the same length */
			l = (int32)MIN((OFF_T)s->blength, len-offset);
			if (l != s->sums[i].len)
				continue;

			if (DEBUG_GTE(DELTASUM, 3)) {
				rprintf(FINFO,
					"potential match at %s i=%ld sum=%08x\n",
					big_num(offset), (long)i, sum);
			}

			if (!done_csum2) {
				map = (schar *)map_ptr(buf,offset,l);
				get_checksum2((char *)map,l,sum2);
				done_csum2 = 1;
			}

			if (memcmp(sum2,s->sums[i].sum2,s->s2length) != 0) {
				false_alarms++;
				continue;
			}

			/* When updating in-place, the best possible match is
			 * one with an identical offset, so we prefer that over
			 * the adjacent want_i optimization. */
			if (updating_basis_file) {
				/* All the generator's chunks start at blength boundaries. */
				while (aligned_offset < offset) {
					aligned_offset += s->blength;
					aligned_i++;
				}
				if ((offset == aligned_offset
				  || (sum == 0 && l == s->blength && aligned_offset + l <= len))
				 && aligned_i < s->count) {
					if (i != aligned_i) {
						if (sum != s->sums[aligned_i].sum1
						 || l != s->sums[aligned_i].len
						 || memcmp(sum2, s->sums[aligned_i].sum2, s->s2length) != 0)
							goto check_want_i;
						i = aligned_i;
					}
					if (offset != aligned_offset) {
						/* We've matched some zeros in a spot that is also zeros
						 * further along in the basis file, if we find zeros ahead
						 * in the sender's file, we'll output enough literal data
						 * to re-align with the basis file, and get back to seeking
						 * instead of writing. */
						backup = (int32)(aligned_offset - last_match);
						if (backup < 0)
							backup = 0;
						map = (schar *)map_ptr(buf, aligned_offset - backup, l + backup)
						    + backup;
						sum = get_checksum1((char *)map, l);
						if (sum != s->sums[i].sum1)
							goto check_want_i;
						get_checksum2((char *)map, l, sum2);
						if (memcmp(sum2, s->sums[i].sum2, s->s2length) != 0)
							goto check_want_i;
						/* OK, we have a re-alignment match.  Bump the offset
						 * forward to the new match point. */
						offset = aligned_offset;
					}
					/* This identical chunk is in the same spot in the old and new file. */
					s->sums[i].flags |= SUMFLG_SAME_OFFSET;
					want_i = i;
				}
			}

		  check_want_i:
			/* we've found a match, but now check to see
			 * if want_i can hint at a better match. */
			if (i != want_i && want_i < s->count
			    && (!updating_basis_file || s->sums[want_i].offset >= offset
			     || s->sums[want_i].flags & SUMFLG_SAME_OFFSET)
			    && sum == s->sums[want_i].sum1
			    && memcmp(sum2, s->sums[want_i].sum2, s->s2length) == 0) {
				/* we've found an adjacent match - the RLL coder
				 * will be happy */
				i = want_i;
			}
			want_i = i + 1;

			matched(f,s,buf,offset,i);
			offset += s->sums[i].len - 1;
			k = (int32)MIN((OFF_T)s->blength, len-offset);
			map = (schar *)map_ptr(buf, offset, k);
			sum = get_checksum1((char *)map, k);
			s1 = sum & 0xFFFF;
			s2 = sum >> 16;
			matches++;
			break;
		} while ((i = s->sums[i].chain) >= 0);

	  null_hash:
		backup = (int32)(offset - last_match);
		/* We sometimes read 1 byte prior to last_match... */
		if (backup < 0)
			backup = 0;

		/* Trim off the first byte from the checksum */
		more = offset + k < len;
		map = (schar *)map_ptr(buf, offset - backup, k + more + backup)
		    + backup;
		s1 -= map[0] + CHAR_OFFSET;
		s2 -= k * (map[0]+CHAR_OFFSET);

		/* Add on the next byte (if there is one) to the checksum */
		if (more) {
			s1 += map[k] + CHAR_OFFSET;
			s2 += s1;
		} else
			--k;

		/* By matching early we avoid re-reading the
		   data 3 times in the case where a token
		   match comes a long way after last
		   match. The 3 reads are caused by the
		   running match, the checksum update and the
		   literal send. */
		if (backup >= s->blength+CHUNK_SIZE && end-offset > CHUNK_SIZE)
			matched(f, s, buf, offset - s->blength, -2);
	} while (++offset < end);

	matched(f, s, buf, len, -1);
	map_ptr(buf, len-1, 1);
}


/**
 * Scan through a origin file, looking for sections that match
 * checksums from the generator, and transmit either literal or token
 * data.
 *
 * Also calculates the MD4 checksum of the whole file, using the md
 * accumulator.  This is transmitted with the file as protection
 * against corruption on the wire.
 *
 * @param s Checksums received from the generator.  If <tt>s->count ==
 * 0</tt>, then there are actually no checksums for this file.
 *
 * @param len Length of the file to send.
 **/
void match_sums(int f, struct sum_struct *s, struct map_struct *buf, OFF_T len)
{
	int sum_len;

	last_match = 0;
	false_alarms = 0;
	hash_hits = 0;
	matches = 0;
	data_transfer = 0;

	sum_init(xfersum_type, checksum_seed);

	if (append_mode > 0) {
		if (append_mode == 2) {
			OFF_T j = 0;
			for (j = CHUNK_SIZE; j < s->flength; j += CHUNK_SIZE) {
				if (buf && INFO_GTE(PROGRESS, 1))
					show_progress(last_match, buf->file_size);
				sum_update(map_ptr(buf, last_match, CHUNK_SIZE),
					   CHUNK_SIZE);
				last_match = j;
			}
			if (last_match < s->flength) {
				int32 n = (int32)(s->flength - last_match);
				if (buf && INFO_GTE(PROGRESS, 1))
					show_progress(last_match, buf->file_size);
				sum_update(map_ptr(buf, last_match, n), n);
			}
		}
		last_match = s->flength;
		s->count = 0;
	}

	if (len > 0 && s->count > 0) {
		build_hash_table(s);

		if (DEBUG_GTE(DELTASUM, 2))
			rprintf(FINFO,"built hash table\n");

		hash_search(f, s, buf, len);

		if (DEBUG_GTE(DELTASUM, 2))
			rprintf(FINFO,"done hash search\n");
	} else {
		OFF_T j;
		/* by doing this in pieces we avoid too many seeks */
		for (j = last_match + CHUNK_SIZE; j < len; j += CHUNK_SIZE)
			matched(f, s, buf, j, -2);
		matched(f, s, buf, len, -1);
	}

	sum_len = sum_end(sender_file_sum);

	/* If we had a read error, send a bad checksum.  We use all bits
	 * off as long as the checksum doesn't happen to be that, in
	 * which case we turn the last 0 bit into a 1. */
	if (buf && buf->status != 0) {
		int i;
		for (i = 0; i < sum_len && sender_file_sum[i] == 0; i++) {}
		memset(sender_file_sum, 0, sum_len);
		if (i == sum_len)
			sender_file_sum[i-1]++;
	}

	if (DEBUG_GTE(DELTASUM, 2))
		rprintf(FINFO,"sending file_sum\n");
	write_buf(f, sender_file_sum, sum_len);

	if (DEBUG_GTE(DELTASUM, 2)) {
		rprintf(FINFO, "false_alarms=%d hash_hits=%d matches=%d\n",
			false_alarms, hash_hits, matches);
	}

	total_hash_hits += hash_hits;
	total_false_alarms += false_alarms;
	total_matches += matches;
	stats.literal_data += data_transfer;
}

void match_report(void)
{
	if (!DEBUG_GTE(DELTASUM, 1))
		return;

	rprintf(FINFO,
		"total: matches=%d  hash_hits=%d  false_alarms=%d data=%s\n",
		total_matches, total_hash_hits, total_false_alarms,
		big_num(stats.literal_data));
}