2
* diff-delta.c: generate a delta between two buffers
4
* This code was greatly inspired by parts of LibXDiff from Davide Libenzi
5
* http://www.xmailserver.org/xdiff-lib.html
7
* Rewritten for GIT by Nicolas Pitre <nico@fluxnic.net>, (C) 2005-2007
8
* Adapted for Bazaar by John Arbash Meinel <john@arbash-meinel.com> (C) 2009
10
* This program is free software; you can redistribute it and/or modify
11
* it under the terms of the GNU General Public License as published by
12
* the Free Software Foundation; either version 2 of the License, or
13
* (at your option) any later version.
15
* NB: The version in GIT is 'version 2 of the Licence only', however Nicolas
16
* has granted permission for use under 'version 2 or later' in private email
17
* to Robert Collins and Karl Fogel on the 6th April 2009.
27
/* maximum hash entry list for the same hash bucket */
30
#define RABIN_SHIFT 23
31
#define RABIN_WINDOW 16
33
/* The hash map is sized to put 4 entries per bucket, this gives us ~even room
34
* for more data. Tweaking this number above 4 doesn't seem to help much,
39
static const unsigned int T[256] = {
40
0x00000000, 0xab59b4d1, 0x56b369a2, 0xfdeadd73, 0x063f6795, 0xad66d344,
41
0x508c0e37, 0xfbd5bae6, 0x0c7ecf2a, 0xa7277bfb, 0x5acda688, 0xf1941259,
42
0x0a41a8bf, 0xa1181c6e, 0x5cf2c11d, 0xf7ab75cc, 0x18fd9e54, 0xb3a42a85,
43
0x4e4ef7f6, 0xe5174327, 0x1ec2f9c1, 0xb59b4d10, 0x48719063, 0xe32824b2,
44
0x1483517e, 0xbfdae5af, 0x423038dc, 0xe9698c0d, 0x12bc36eb, 0xb9e5823a,
45
0x440f5f49, 0xef56eb98, 0x31fb3ca8, 0x9aa28879, 0x6748550a, 0xcc11e1db,
46
0x37c45b3d, 0x9c9defec, 0x6177329f, 0xca2e864e, 0x3d85f382, 0x96dc4753,
47
0x6b369a20, 0xc06f2ef1, 0x3bba9417, 0x90e320c6, 0x6d09fdb5, 0xc6504964,
48
0x2906a2fc, 0x825f162d, 0x7fb5cb5e, 0xd4ec7f8f, 0x2f39c569, 0x846071b8,
49
0x798aaccb, 0xd2d3181a, 0x25786dd6, 0x8e21d907, 0x73cb0474, 0xd892b0a5,
50
0x23470a43, 0x881ebe92, 0x75f463e1, 0xdeadd730, 0x63f67950, 0xc8afcd81,
51
0x354510f2, 0x9e1ca423, 0x65c91ec5, 0xce90aa14, 0x337a7767, 0x9823c3b6,
52
0x6f88b67a, 0xc4d102ab, 0x393bdfd8, 0x92626b09, 0x69b7d1ef, 0xc2ee653e,
53
0x3f04b84d, 0x945d0c9c, 0x7b0be704, 0xd05253d5, 0x2db88ea6, 0x86e13a77,
54
0x7d348091, 0xd66d3440, 0x2b87e933, 0x80de5de2, 0x7775282e, 0xdc2c9cff,
55
0x21c6418c, 0x8a9ff55d, 0x714a4fbb, 0xda13fb6a, 0x27f92619, 0x8ca092c8,
56
0x520d45f8, 0xf954f129, 0x04be2c5a, 0xafe7988b, 0x5432226d, 0xff6b96bc,
57
0x02814bcf, 0xa9d8ff1e, 0x5e738ad2, 0xf52a3e03, 0x08c0e370, 0xa39957a1,
58
0x584ced47, 0xf3155996, 0x0eff84e5, 0xa5a63034, 0x4af0dbac, 0xe1a96f7d,
59
0x1c43b20e, 0xb71a06df, 0x4ccfbc39, 0xe79608e8, 0x1a7cd59b, 0xb125614a,
60
0x468e1486, 0xedd7a057, 0x103d7d24, 0xbb64c9f5, 0x40b17313, 0xebe8c7c2,
61
0x16021ab1, 0xbd5bae60, 0x6cb54671, 0xc7ecf2a0, 0x3a062fd3, 0x915f9b02,
62
0x6a8a21e4, 0xc1d39535, 0x3c394846, 0x9760fc97, 0x60cb895b, 0xcb923d8a,
63
0x3678e0f9, 0x9d215428, 0x66f4eece, 0xcdad5a1f, 0x3047876c, 0x9b1e33bd,
64
0x7448d825, 0xdf116cf4, 0x22fbb187, 0x89a20556, 0x7277bfb0, 0xd92e0b61,
65
0x24c4d612, 0x8f9d62c3, 0x7836170f, 0xd36fa3de, 0x2e857ead, 0x85dcca7c,
66
0x7e09709a, 0xd550c44b, 0x28ba1938, 0x83e3ade9, 0x5d4e7ad9, 0xf617ce08,
67
0x0bfd137b, 0xa0a4a7aa, 0x5b711d4c, 0xf028a99d, 0x0dc274ee, 0xa69bc03f,
68
0x5130b5f3, 0xfa690122, 0x0783dc51, 0xacda6880, 0x570fd266, 0xfc5666b7,
69
0x01bcbbc4, 0xaae50f15, 0x45b3e48d, 0xeeea505c, 0x13008d2f, 0xb85939fe,
70
0x438c8318, 0xe8d537c9, 0x153feaba, 0xbe665e6b, 0x49cd2ba7, 0xe2949f76,
71
0x1f7e4205, 0xb427f6d4, 0x4ff24c32, 0xe4abf8e3, 0x19412590, 0xb2189141,
72
0x0f433f21, 0xa41a8bf0, 0x59f05683, 0xf2a9e252, 0x097c58b4, 0xa225ec65,
73
0x5fcf3116, 0xf49685c7, 0x033df00b, 0xa86444da, 0x558e99a9, 0xfed72d78,
74
0x0502979e, 0xae5b234f, 0x53b1fe3c, 0xf8e84aed, 0x17bea175, 0xbce715a4,
75
0x410dc8d7, 0xea547c06, 0x1181c6e0, 0xbad87231, 0x4732af42, 0xec6b1b93,
76
0x1bc06e5f, 0xb099da8e, 0x4d7307fd, 0xe62ab32c, 0x1dff09ca, 0xb6a6bd1b,
77
0x4b4c6068, 0xe015d4b9, 0x3eb80389, 0x95e1b758, 0x680b6a2b, 0xc352defa,
78
0x3887641c, 0x93ded0cd, 0x6e340dbe, 0xc56db96f, 0x32c6cca3, 0x999f7872,
79
0x6475a501, 0xcf2c11d0, 0x34f9ab36, 0x9fa01fe7, 0x624ac294, 0xc9137645,
80
0x26459ddd, 0x8d1c290c, 0x70f6f47f, 0xdbaf40ae, 0x207afa48, 0x8b234e99,
81
0x76c993ea, 0xdd90273b, 0x2a3b52f7, 0x8162e626, 0x7c883b55, 0xd7d18f84,
82
0x2c043562, 0x875d81b3, 0x7ab75cc0, 0xd1eee811
85
static const unsigned int U[256] = {
86
0x00000000, 0x7eb5200d, 0x5633f4cb, 0x2886d4c6, 0x073e5d47, 0x798b7d4a,
87
0x510da98c, 0x2fb88981, 0x0e7cba8e, 0x70c99a83, 0x584f4e45, 0x26fa6e48,
88
0x0942e7c9, 0x77f7c7c4, 0x5f711302, 0x21c4330f, 0x1cf9751c, 0x624c5511,
89
0x4aca81d7, 0x347fa1da, 0x1bc7285b, 0x65720856, 0x4df4dc90, 0x3341fc9d,
90
0x1285cf92, 0x6c30ef9f, 0x44b63b59, 0x3a031b54, 0x15bb92d5, 0x6b0eb2d8,
91
0x4388661e, 0x3d3d4613, 0x39f2ea38, 0x4747ca35, 0x6fc11ef3, 0x11743efe,
92
0x3eccb77f, 0x40799772, 0x68ff43b4, 0x164a63b9, 0x378e50b6, 0x493b70bb,
93
0x61bda47d, 0x1f088470, 0x30b00df1, 0x4e052dfc, 0x6683f93a, 0x1836d937,
94
0x250b9f24, 0x5bbebf29, 0x73386bef, 0x0d8d4be2, 0x2235c263, 0x5c80e26e,
95
0x740636a8, 0x0ab316a5, 0x2b7725aa, 0x55c205a7, 0x7d44d161, 0x03f1f16c,
96
0x2c4978ed, 0x52fc58e0, 0x7a7a8c26, 0x04cfac2b, 0x73e5d470, 0x0d50f47d,
97
0x25d620bb, 0x5b6300b6, 0x74db8937, 0x0a6ea93a, 0x22e87dfc, 0x5c5d5df1,
98
0x7d996efe, 0x032c4ef3, 0x2baa9a35, 0x551fba38, 0x7aa733b9, 0x041213b4,
99
0x2c94c772, 0x5221e77f, 0x6f1ca16c, 0x11a98161, 0x392f55a7, 0x479a75aa,
100
0x6822fc2b, 0x1697dc26, 0x3e1108e0, 0x40a428ed, 0x61601be2, 0x1fd53bef,
101
0x3753ef29, 0x49e6cf24, 0x665e46a5, 0x18eb66a8, 0x306db26e, 0x4ed89263,
102
0x4a173e48, 0x34a21e45, 0x1c24ca83, 0x6291ea8e, 0x4d29630f, 0x339c4302,
103
0x1b1a97c4, 0x65afb7c9, 0x446b84c6, 0x3adea4cb, 0x1258700d, 0x6ced5000,
104
0x4355d981, 0x3de0f98c, 0x15662d4a, 0x6bd30d47, 0x56ee4b54, 0x285b6b59,
105
0x00ddbf9f, 0x7e689f92, 0x51d01613, 0x2f65361e, 0x07e3e2d8, 0x7956c2d5,
106
0x5892f1da, 0x2627d1d7, 0x0ea10511, 0x7014251c, 0x5facac9d, 0x21198c90,
107
0x099f5856, 0x772a785b, 0x4c921c31, 0x32273c3c, 0x1aa1e8fa, 0x6414c8f7,
108
0x4bac4176, 0x3519617b, 0x1d9fb5bd, 0x632a95b0, 0x42eea6bf, 0x3c5b86b2,
109
0x14dd5274, 0x6a687279, 0x45d0fbf8, 0x3b65dbf5, 0x13e30f33, 0x6d562f3e,
110
0x506b692d, 0x2ede4920, 0x06589de6, 0x78edbdeb, 0x5755346a, 0x29e01467,
111
0x0166c0a1, 0x7fd3e0ac, 0x5e17d3a3, 0x20a2f3ae, 0x08242768, 0x76910765,
112
0x59298ee4, 0x279caee9, 0x0f1a7a2f, 0x71af5a22, 0x7560f609, 0x0bd5d604,
113
0x235302c2, 0x5de622cf, 0x725eab4e, 0x0ceb8b43, 0x246d5f85, 0x5ad87f88,
114
0x7b1c4c87, 0x05a96c8a, 0x2d2fb84c, 0x539a9841, 0x7c2211c0, 0x029731cd,
115
0x2a11e50b, 0x54a4c506, 0x69998315, 0x172ca318, 0x3faa77de, 0x411f57d3,
116
0x6ea7de52, 0x1012fe5f, 0x38942a99, 0x46210a94, 0x67e5399b, 0x19501996,
117
0x31d6cd50, 0x4f63ed5d, 0x60db64dc, 0x1e6e44d1, 0x36e89017, 0x485db01a,
118
0x3f77c841, 0x41c2e84c, 0x69443c8a, 0x17f11c87, 0x38499506, 0x46fcb50b,
119
0x6e7a61cd, 0x10cf41c0, 0x310b72cf, 0x4fbe52c2, 0x67388604, 0x198da609,
120
0x36352f88, 0x48800f85, 0x6006db43, 0x1eb3fb4e, 0x238ebd5d, 0x5d3b9d50,
121
0x75bd4996, 0x0b08699b, 0x24b0e01a, 0x5a05c017, 0x728314d1, 0x0c3634dc,
122
0x2df207d3, 0x534727de, 0x7bc1f318, 0x0574d315, 0x2acc5a94, 0x54797a99,
123
0x7cffae5f, 0x024a8e52, 0x06852279, 0x78300274, 0x50b6d6b2, 0x2e03f6bf,
124
0x01bb7f3e, 0x7f0e5f33, 0x57888bf5, 0x293dabf8, 0x08f998f7, 0x764cb8fa,
125
0x5eca6c3c, 0x207f4c31, 0x0fc7c5b0, 0x7172e5bd, 0x59f4317b, 0x27411176,
126
0x1a7c5765, 0x64c97768, 0x4c4fa3ae, 0x32fa83a3, 0x1d420a22, 0x63f72a2f,
127
0x4b71fee9, 0x35c4dee4, 0x1400edeb, 0x6ab5cde6, 0x42331920, 0x3c86392d,
128
0x133eb0ac, 0x6d8b90a1, 0x450d4467, 0x3bb8646a
132
const unsigned char *ptr;
133
const struct source_info *src;
137
struct index_entry_linked_list {
138
struct index_entry *p_entry;
139
struct index_entry_linked_list *next;
142
struct unpacked_index_entry {
143
struct index_entry entry;
144
struct unpacked_index_entry *next;
148
unsigned long memsize; /* Total bytes pointed to by this index */
149
const struct source_info *last_src; /* Information about the referenced source */
150
unsigned int hash_mask; /* val & hash_mask gives the hash index for a given
152
unsigned int num_entries; /* The total number of entries in this index */
153
struct index_entry *last_entry; /* Pointer to the last valid entry */
154
struct index_entry *hash[];
158
limit_hash_buckets(struct unpacked_index_entry **hash,
159
unsigned int *hash_count, unsigned int hsize,
160
unsigned int entries)
162
struct unpacked_index_entry *entry;
165
* Determine a limit on the number of entries in the same hash
166
* bucket. This guards us against pathological data sets causing
167
* really bad hash distribution with most entries in the same hash
168
* bucket that would bring us to O(m*n) computing costs (m and n
169
* corresponding to reference and target buffer sizes).
171
* Make sure none of the hash buckets has more entries than
172
* we're willing to test. Otherwise we cull the entry list
173
* uniformly to still preserve a good repartition across
174
* the reference buffer.
176
for (i = 0; i < hsize; i++) {
179
if (hash_count[i] <= HASH_LIMIT)
182
/* We leave exactly HASH_LIMIT entries in the bucket */
183
entries -= hash_count[i] - HASH_LIMIT;
189
* Assume that this loop is gone through exactly
190
* HASH_LIMIT times and is entered and left with
191
* acc==0. So the first statement in the loop
192
* contributes (hash_count[i]-HASH_LIMIT)*HASH_LIMIT
193
* to the accumulator, and the inner loop consequently
194
* is run (hash_count[i]-HASH_LIMIT) times, removing
195
* one element from the list each time. Since acc
196
* balances out to 0 at the final run, the inner loop
197
* body can't be left with entry==NULL. So we indeed
198
* encounter entry==NULL in the outer loop only.
201
acc += hash_count[i] - HASH_LIMIT;
203
struct unpacked_index_entry *keep = entry;
208
keep->next = entry->next;
216
static struct delta_index *
217
pack_delta_index(struct unpacked_index_entry **hash, unsigned int hsize,
218
unsigned int num_entries, struct delta_index *old_index)
220
unsigned int i, j, hmask, memsize, fit_in_old, copied_count;
221
struct unpacked_index_entry *entry;
222
struct delta_index *index;
223
struct index_entry *packed_entry, **packed_hash, *old_entry, *copy_from;
224
struct index_entry null_entry = {0};
230
// fprintf(stderr, "Packing %d entries into %d for total of %d entries"
232
// num_entries - old_index->num_entries,
233
// old_index->num_entries, num_entries,
234
// old_index->hash_mask, hmask);
236
// fprintf(stderr, "Packing %d entries into a new index\n",
239
/* First, see if we can squeeze the new items into the existing structure.
243
if (old_index && old_index->hash_mask == hmask) {
245
for (i = 0; i < hsize; ++i) {
247
for (entry = hash[i]; entry; entry = entry->next) {
248
if (packed_entry == NULL) {
249
/* Find the last open spot */
250
packed_entry = old_index->hash[i + 1];
252
while (packed_entry >= old_index->hash[i]
253
&& packed_entry->ptr == NULL) {
258
if (packed_entry >= old_index->hash[i+1]
259
|| packed_entry->ptr != NULL) {
260
/* There are no free spots here :( */
264
/* We found an empty spot to put this entry
265
* Copy it over, and remove it from the linked list, just in
266
* case we end up running out of room later.
268
*packed_entry++ = entry->entry;
269
assert(entry == hash[i]);
270
hash[i] = entry->next;
272
old_index->num_entries++;
281
// fprintf(stderr, "Fit all %d entries into old index\n",
284
* No need to allocate a new buffer, but return old_index ptr so
285
* callers can distinguish this from an OOM failure.
289
// fprintf(stderr, "Fit only %d entries into old index,"
290
// " reallocating\n", copied_count);
294
* Now create the packed index in array form
295
* rather than linked lists.
296
* Leave a 2-entry gap for inserting more entries between the groups
298
memsize = sizeof(*index)
299
+ sizeof(*packed_hash) * (hsize+1)
300
+ sizeof(*packed_entry) * (num_entries + hsize * EXTRA_NULLS);
301
mem = malloc(memsize);
307
index->memsize = memsize;
308
index->hash_mask = hmask;
309
index->num_entries = num_entries;
311
if (hmask < old_index->hash_mask) {
312
fprintf(stderr, "hash mask was shrunk %x => %x\n",
313
old_index->hash_mask, hmask);
315
assert(hmask >= old_index->hash_mask);
320
mem = packed_hash + (hsize+1);
323
for (i = 0; i < hsize; i++) {
325
* Coalesce all entries belonging to one linked list
326
* into consecutive array entries.
328
packed_hash[i] = packed_entry;
329
/* Old comes earlier as a source, so it always comes first in a given
333
/* Could we optimize this to use memcpy when hmask ==
334
* old_index->hash_mask? Would it make any real difference?
336
j = i & old_index->hash_mask;
337
copy_from = old_index->hash[j];
338
for (old_entry = old_index->hash[j];
339
old_entry < old_index->hash[j + 1] && old_entry->ptr != NULL;
341
if ((old_entry->val & hmask) == i) {
342
*packed_entry++ = *old_entry;
346
for (entry = hash[i]; entry; entry = entry->next) {
347
*packed_entry++ = entry->entry;
349
/* TODO: At this point packed_entry - packed_hash[i] is the number of
350
* records that we have inserted into this hash bucket.
351
* We should *really* consider doing some limiting along the
352
* lines of limit_hash_buckets() to avoid pathological behavior.
354
/* Now add extra 'NULL' entries that we can use for future expansion. */
355
for (j = 0; j < EXTRA_NULLS; ++j ) {
356
*packed_entry++ = null_entry;
360
/* Sentinel value to indicate the length of the last hash bucket */
361
packed_hash[hsize] = packed_entry;
363
if (packed_entry - (struct index_entry *)mem
364
!= num_entries + hsize*EXTRA_NULLS) {
365
fprintf(stderr, "We expected %d entries, but created %d\n",
366
num_entries + hsize*EXTRA_NULLS,
367
(int)(packed_entry - (struct index_entry*)mem));
369
assert(packed_entry - (struct index_entry *)mem
370
== num_entries + hsize*EXTRA_NULLS);
371
index->last_entry = (packed_entry - 1);
377
create_delta_index(const struct source_info *src,
378
struct delta_index *old,
379
struct delta_index **fresh)
381
unsigned int i, hsize, hmask, num_entries, prev_val, *hash_count;
382
unsigned int total_num_entries;
383
const unsigned char *data, *buffer;
384
struct delta_index *index;
385
struct unpacked_index_entry *entry, **hash;
387
unsigned long memsize;
389
if (!src->buf || !src->size)
390
return DELTA_SOURCE_EMPTY;
393
/* Determine index hash size. Note that indexing skips the
394
first byte to allow for optimizing the Rabin's polynomial
395
initialization in create_delta(). */
396
num_entries = (src->size - 1) / RABIN_WINDOW;
398
total_num_entries = num_entries + old->num_entries;
400
total_num_entries = num_entries;
401
hsize = total_num_entries / 4;
402
for (i = 4; (1u << i) < hsize && i < 31; i++);
405
if (old && old->hash_mask > hmask) {
406
hmask = old->hash_mask;
410
/* allocate lookup index */
411
memsize = sizeof(*hash) * hsize +
412
sizeof(*entry) * total_num_entries;
413
mem = malloc(memsize);
415
return DELTA_OUT_OF_MEMORY;
420
memset(hash, 0, hsize * sizeof(*hash));
422
/* allocate an array to count hash num_entries */
423
hash_count = calloc(hsize, sizeof(*hash_count));
426
return DELTA_OUT_OF_MEMORY;
429
/* then populate the index for the new data */
431
for (data = buffer + num_entries * RABIN_WINDOW - RABIN_WINDOW;
433
data -= RABIN_WINDOW) {
434
unsigned int val = 0;
435
for (i = 1; i <= RABIN_WINDOW; i++)
436
val = ((val << 8) | data[i]) ^ T[val >> RABIN_SHIFT];
437
if (val == prev_val) {
438
/* keep the lowest of consecutive identical blocks */
439
entry[-1].entry.ptr = data + RABIN_WINDOW;
445
entry->entry.ptr = data + RABIN_WINDOW;
446
entry->entry.val = val;
447
entry->entry.src = src;
448
entry->next = hash[i];
453
/* TODO: It would be nice to limit_hash_buckets at a better time. */
454
total_num_entries = limit_hash_buckets(hash, hash_count, hsize,
457
index = pack_delta_index(hash, hsize, total_num_entries, old);
459
/* pack_delta_index only returns NULL on malloc failure */
461
return DELTA_OUT_OF_MEMORY;
463
index->last_src = src;
468
/* Take some entries, and put them into a custom hash.
469
* @param entries A list of entries, sorted by position in file
470
* @param num_entries Length of entries
471
* @param out_hsize The maximum size of the hash, the final size will be
474
struct index_entry_linked_list **
475
_put_entries_into_hash(struct index_entry *entries, unsigned int num_entries,
478
unsigned int hash_offset, hmask, memsize;
479
struct index_entry *entry, *last_entry;
480
struct index_entry_linked_list *out_entry, **hash;
485
memsize = sizeof(*hash) * hsize +
486
sizeof(*out_entry) * num_entries;
487
mem = malloc(memsize);
494
memset(hash, 0, sizeof(*hash)*(hsize+1));
496
/* We know that entries are in the order we want in the output, but they
497
* aren't "grouped" by hash bucket yet.
499
last_entry = entries + num_entries;
500
for (entry = entries + num_entries - 1; entry >= entries; --entry) {
501
hash_offset = entry->val & hmask;
502
out_entry->p_entry = entry;
503
out_entry->next = hash[hash_offset];
504
/* TODO: Remove entries that have identical vals, or at least filter
505
* the map a little bit.
506
* if (hash[i] != NULL) {
509
hash[hash_offset] = out_entry;
517
create_index_from_old_and_new_entries(const struct delta_index *old_index,
518
struct index_entry *entries,
519
unsigned int num_entries)
521
unsigned int i, j, hsize, hmask, total_num_entries;
522
struct delta_index *index;
523
struct index_entry *entry, *packed_entry, **packed_hash;
524
struct index_entry *last_entry, null_entry = {0};
526
unsigned long memsize;
527
struct index_entry_linked_list *unpacked_entry, **mini_hash;
529
/* Determine index hash size. Note that indexing skips the
530
first byte to allow for optimizing the Rabin's polynomial
531
initialization in create_delta(). */
532
total_num_entries = num_entries + old_index->num_entries;
533
hsize = total_num_entries / 4;
534
for (i = 4; (1u << i) < hsize && i < 31; i++);
536
if (hsize < old_index->hash_mask) {
537
/* For some reason, there was a code path that would actually *shrink*
538
* the hash size. This screws with some later code, and in general, I
539
* think it better to make the hash bigger, rather than smaller. So
540
* we'll just force the size here.
541
* Possibly done by create_delta_index running into a
542
* limit_hash_buckets call, that ended up transitioning across a
543
* power-of-2. The cause isn't 100% clear, though.
545
hsize = old_index->hash_mask + 1;
548
// fprintf(stderr, "resizing index to insert %d entries into array"
549
// " with %d entries: %x => %x\n",
550
// num_entries, old_index->num_entries, old_index->hash_mask, hmask);
552
memsize = sizeof(*index)
553
+ sizeof(*packed_hash) * (hsize+1)
554
+ sizeof(*packed_entry) * (total_num_entries + hsize*EXTRA_NULLS);
555
mem = malloc(memsize);
560
index->memsize = memsize;
561
index->hash_mask = hmask;
562
index->num_entries = total_num_entries;
563
index->last_src = old_index->last_src;
567
mem = packed_hash + (hsize+1);
570
mini_hash = _put_entries_into_hash(entries, num_entries, hsize);
571
if (mini_hash == NULL) {
575
last_entry = entries + num_entries;
576
for (i = 0; i < hsize; i++) {
578
* Coalesce all entries belonging in one hash bucket
579
* into consecutive array entries.
580
* The entries in old_index all come before 'entries'.
582
packed_hash[i] = packed_entry;
583
/* Copy any of the old entries across */
584
/* Would we rather use memcpy? */
585
if (hmask == old_index->hash_mask) {
586
for (entry = old_index->hash[i];
587
entry < old_index->hash[i+1] && entry->ptr != NULL;
589
assert((entry->val & hmask) == i);
590
*packed_entry++ = *entry;
593
/* If we resized the index from this action, all of the old values
594
* will be found in the previous location, but they will end up
595
* spread across the new locations.
597
j = i & old_index->hash_mask;
598
for (entry = old_index->hash[j];
599
entry < old_index->hash[j+1] && entry->ptr != NULL;
601
assert((entry->val & old_index->hash_mask) == j);
602
if ((entry->val & hmask) == i) {
603
/* Any entries not picked up here will be picked up on the
606
*packed_entry++ = *entry;
610
/* Now see if we need to insert any of the new entries.
611
* Note that loop ends up O(hsize*num_entries), so we expect that
612
* num_entries is always small.
613
* We also help a little bit by collapsing the entry range when the
614
* endpoints are inserted. However, an alternative would be to build a
615
* quick hash lookup for just the new entries.
616
* Testing shows that this list can easily get up to about 100
617
* entries, the tradeoff is a malloc, 1 pass over the entries, copying
618
* them into a sorted buffer, and a free() when done,
620
for (unpacked_entry = mini_hash[i];
622
unpacked_entry = unpacked_entry->next) {
623
assert((unpacked_entry->p_entry->val & hmask) == i);
624
*packed_entry++ = *(unpacked_entry->p_entry);
626
/* Now insert some extra nulls */
627
for (j = 0; j < EXTRA_NULLS; ++j) {
628
*packed_entry++ = null_entry;
633
/* Sentinel value to indicate the length of the last hash bucket */
634
packed_hash[hsize] = packed_entry;
636
if ((packed_entry - (struct index_entry *)mem)
637
!= (total_num_entries + hsize*EXTRA_NULLS)) {
638
fprintf(stderr, "We expected %d entries, but created %d\n",
639
total_num_entries + hsize*EXTRA_NULLS,
640
(int)(packed_entry - (struct index_entry*)mem));
643
assert((packed_entry - (struct index_entry *)mem)
644
== (total_num_entries + hsize * EXTRA_NULLS));
645
index->last_entry = (packed_entry - 1);
651
get_text(char buff[128], const unsigned char *ptr)
654
const unsigned char *start;
656
start = (ptr-RABIN_WINDOW-1);
658
if (cmd < 0x80) {// This is likely to be an insert instruction
659
if (cmd < RABIN_WINDOW) {
663
/* This was either a copy [should never be] or it
664
* was a longer insert so the insert start happened at 16 more
667
cmd = RABIN_WINDOW + 1;
670
cmd = 60; /* Be friendly to 80char terms */
672
/* Copy the 1 byte command, and 4 bytes after the insert */
674
memcpy(buff, start, cmd);
676
for (i = 0; i < cmd; ++i) {
677
if (buff[i] == '\n') {
679
} else if (buff[i] == '\t') {
686
create_delta_index_from_delta(const struct source_info *src,
687
struct delta_index *old_index,
688
struct delta_index **fresh)
690
unsigned int i, num_entries, max_num_entries, prev_val, num_inserted;
691
unsigned int hash_offset;
692
const unsigned char *data, *buffer, *top;
694
struct delta_index *new_index;
695
struct index_entry *entry, *entries;
698
return DELTA_INDEX_NEEDED;
699
if (!src->buf || !src->size)
700
return DELTA_SOURCE_EMPTY;
702
top = buffer + src->size;
704
/* Determine index hash size. Note that indexing skips the
705
first byte to allow for optimizing the Rabin's polynomial
706
initialization in create_delta().
707
This computes the maximum number of entries that could be held. The
708
actual number will be recomputed during processing.
711
max_num_entries = (src->size - 1) / RABIN_WINDOW;
713
/* allocate an array to hold whatever entries we find */
714
entries = malloc(sizeof(*entry) * max_num_entries);
715
if (!entries) /* malloc failure */
716
return DELTA_OUT_OF_MEMORY;
718
/* then populate the index for the new data */
722
/* get_delta_hdr_size doesn't mutate the content, just moves the
723
* start-of-data pointer, so it is safe to do the cast.
725
get_delta_hdr_size((unsigned char**)&data, top);
726
entry = entries; /* start at the first slot */
727
num_entries = 0; /* calculate the real number of entries */
731
/* Copy instruction, skip it */
732
if (cmd & 0x01) data++;
733
if (cmd & 0x02) data++;
734
if (cmd & 0x04) data++;
735
if (cmd & 0x08) data++;
736
if (cmd & 0x10) data++;
737
if (cmd & 0x20) data++;
738
if (cmd & 0x40) data++;
740
/* Insert instruction, we want to index these bytes */
741
if (data + cmd > top) {
742
/* Invalid insert, not enough bytes in the delta */
745
/* The create_delta code requires a match at least 4 characters
746
* (including only the last char of the RABIN_WINDOW) before it
747
* will consider it something worth copying rather than inserting.
748
* So we don't want to index anything that we know won't ever be a
751
for (; cmd > RABIN_WINDOW + 3; cmd -= RABIN_WINDOW,
752
data += RABIN_WINDOW) {
753
unsigned int val = 0;
754
for (i = 1; i <= RABIN_WINDOW; i++)
755
val = ((val << 8) | data[i]) ^ T[val >> RABIN_SHIFT];
756
if (val != prev_val) {
757
/* Only keep the first of consecutive data */
760
entry->ptr = data + RABIN_WINDOW;
764
if (num_entries > max_num_entries) {
765
/* We ran out of entry room, something is really wrong
771
/* Move the data pointer by whatever remainder is left */
775
* cmd == 0 is reserved for future encoding
776
* extensions. In the mean time we must fail when
777
* encountering them (might be data corruption).
783
/* The source_info data passed was corrupted or otherwise invalid */
785
return DELTA_SOURCE_BAD;
787
if (num_entries == 0) {
788
/** Nothing to index **/
793
old_index->last_src = src;
794
/* See if we can fill in these values into the holes in the array */
797
for (; num_entries > 0; --num_entries, ++entry) {
798
struct index_entry *next_bucket_entry, *cur_entry, *bucket_first_entry;
799
hash_offset = (entry->val & old_index->hash_mask);
800
/* The basic structure is a hash => packed_entries that fit in that
801
* hash bucket. Things are structured such that the hash-pointers are
802
* strictly ordered. So we start by pointing to the next pointer, and
803
* walk back until we stop getting NULL targets, and then go back
804
* forward. If there are no NULL targets, then we know because
805
* entry->ptr will not be NULL.
807
// The start of the next bucket, this may point past the end of the
808
// entry table if hash_offset is the last bucket.
809
next_bucket_entry = old_index->hash[hash_offset + 1];
810
// First entry in this bucket
811
bucket_first_entry = old_index->hash[hash_offset];
812
cur_entry = next_bucket_entry - 1;
813
while (cur_entry->ptr == NULL && cur_entry >= bucket_first_entry) {
816
// cur_entry now either points at the first NULL, or it points to
817
// next_bucket_entry if there were no blank spots.
819
if (cur_entry >= next_bucket_entry || cur_entry->ptr != NULL) {
820
/* There is no room for this entry, we have to resize */
822
// get_text(buff, entry->ptr);
823
// fprintf(stderr, "Failed to find an opening @%x for %8x:\n '%s'\n",
824
// hash_offset, entry->val, buff);
825
// for (old_entry = old_index->hash[hash_offset];
826
// old_entry < old_index->hash[hash_offset+1];
828
// get_text(buff, old_entry->ptr);
829
// fprintf(stderr, " [%2d] %8x %8x: '%s'\n",
830
// (int)(old_entry - old_index->hash[hash_offset]),
831
// old_entry->val, old_entry->ptr, buff);
837
/* For entries which we *do* manage to insert into old_index, we don't
838
* want them double copied into the final output.
840
old_index->num_entries++;
842
if (num_entries > 0) {
843
/* We couldn't fit the new entries into the old index, so allocate a
844
* new one, and fill it with stuff.
846
// fprintf(stderr, "inserted %d before resize\n", num_inserted);
847
new_index = create_index_from_old_and_new_entries(old_index,
850
new_index = old_index;
851
// fprintf(stderr, "inserted %d without resizing\n", num_inserted);
854
/* create_index_from_old_and_new_entries returns NULL on malloc failure */
856
return DELTA_OUT_OF_MEMORY;
861
void free_delta_index(struct delta_index *index)
867
sizeof_delta_index(struct delta_index *index)
870
return index->memsize;
876
* The maximum size for any opcode sequence, including the initial header
877
* plus Rabin window plus biggest copy.
879
#define MAX_OP_SIZE (5 + 5 + 1 + RABIN_WINDOW + 7)
882
create_delta(const struct delta_index *index,
883
const void *trg_buf, unsigned long trg_size,
884
unsigned long *delta_size, unsigned long max_size,
887
unsigned int i, outpos, outsize, moff, val;
889
const struct source_info *msource;
891
const unsigned char *ref_data, *ref_top, *data, *top;
893
unsigned long source_size;
895
if (!trg_buf || !trg_size)
896
return DELTA_BUFFER_EMPTY;
898
return DELTA_INDEX_NEEDED;
902
if (max_size && outsize >= max_size)
903
outsize = max_size + MAX_OP_SIZE + 1;
904
out = malloc(outsize);
906
return DELTA_OUT_OF_MEMORY;
908
source_size = index->last_src->size + index->last_src->agg_offset;
910
/* store target buffer size */
913
out[outpos++] = i | 0x80;
919
top = (const unsigned char *) trg_buf + trg_size;
921
/* Start the matching by filling out with a simple 'insert' instruction, of
922
* the first RABIN_WINDOW bytes of the input.
924
outpos++; /* leave a byte for the insert command */
926
for (i = 0; i < RABIN_WINDOW && data < top; i++, data++) {
927
out[outpos++] = *data;
928
val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT];
930
/* we are now setup with an insert of 'i' bytes and val contains the RABIN
931
* hash for those bytes, and data points to the RABIN_WINDOW+1 byte of
941
/* we don't have a 'worthy enough' match yet, so let's look for
944
struct index_entry *entry;
945
/* Shift the window by one byte. */
946
val ^= U[data[-RABIN_WINDOW]];
947
val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT];
948
i = val & index->hash_mask;
949
/* TODO: When using multiple indexes like this, the hash tables
950
* mapping val => index_entry become less efficient.
951
* You end up getting a lot more collisions in the hash,
952
* which doesn't actually lead to a entry->val match.
954
for (entry = index->hash[i];
955
entry < index->hash[i+1] && entry->src != NULL;
957
const unsigned char *ref;
958
const unsigned char *src;
960
if (entry->val != val)
964
ref_data = entry->src->buf;
965
ref_top = ref_data + entry->src->size;
966
ref_size = ref_top - ref;
967
/* ref_size is the longest possible match that we could make
968
* here. If ref_size <= msize, then we know that we cannot
969
* match more bytes with this location that we have already
972
if (ref_size > (top - src))
973
ref_size = top - src;
974
if (ref_size <= msize)
976
/* See how many bytes actually match at this location. */
977
while (ref_size-- && *src++ == *ref)
979
if (msize < (ref - entry->ptr)) {
980
/* this is our best match so far */
981
msize = ref - entry->ptr;
982
msource = entry->src;
983
moff = entry->ptr - ref_data;
984
if (msize >= 4096) /* good enough */
991
/* The best match right now is less than 4 bytes long. So just add
992
* the current byte to the insert instruction. Increment the insert
993
* counter, and copy the byte of data into the output buffer.
997
out[outpos++] = *data++;
999
if (inscnt == 0x7f) {
1000
/* We have a max length insert instruction, finalize it in the
1003
out[outpos - inscnt - 1] = inscnt;
1012
ref_data = msource->buf;
1013
while (moff && ref_data[moff-1] == data[-1]) {
1014
/* we can match one byte back */
1021
outpos--; /* remove count slot */
1022
inscnt--; /* make it -1 */
1025
out[outpos - inscnt - 1] = inscnt;
1029
/* A copy op is currently limited to 64KB (pack v2) */
1030
left = (msize < 0x10000) ? 0 : (msize - 0x10000);
1033
op = out + outpos++;
1036
/* moff is the offset in the local structure, for encoding, we need
1037
* to push it into the global offset
1039
assert(moff < msource->size);
1040
moff += msource->agg_offset;
1041
assert(moff + msize <= source_size);
1042
if (moff & 0x000000ff)
1043
out[outpos++] = moff >> 0, i |= 0x01;
1044
if (moff & 0x0000ff00)
1045
out[outpos++] = moff >> 8, i |= 0x02;
1046
if (moff & 0x00ff0000)
1047
out[outpos++] = moff >> 16, i |= 0x04;
1048
if (moff & 0xff000000)
1049
out[outpos++] = moff >> 24, i |= 0x08;
1050
/* Put it back into local coordinates, in case we have multiple
1053
moff -= msource->agg_offset;
1056
out[outpos++] = msize >> 0, i |= 0x10;
1058
out[outpos++] = msize >> 8, i |= 0x20;
1069
for (j = -RABIN_WINDOW; j < 0; j++)
1070
val = ((val << 8) | data[j])
1071
^ T[val >> RABIN_SHIFT];
1075
if (outpos >= outsize - MAX_OP_SIZE) {
1077
outsize = outsize * 3 / 2;
1078
if (max_size && outsize >= max_size)
1079
outsize = max_size + MAX_OP_SIZE + 1;
1080
if (max_size && outpos > max_size)
1082
out = realloc(out, outsize);
1085
return DELTA_OUT_OF_MEMORY;
1091
out[outpos - inscnt - 1] = inscnt;
1093
if (max_size && outpos > max_size) {
1095
return DELTA_SIZE_TOO_BIG;
1098
*delta_size = outpos;
1103
/* vim: et ts=4 sw=4 sts=4
added
removed
bzrlib/diff-delta.c
