diff options
Diffstat (limited to 'diff-delta.c')
| -rw-r--r-- | diff-delta.c | 482 |
1 files changed, 482 insertions, 0 deletions
diff --git a/diff-delta.c b/diff-delta.c new file mode 100644 index 0000000000..a4e28df714 --- /dev/null +++ b/diff-delta.c @@ -0,0 +1,482 @@ +/* + * diff-delta.c: generate a delta between two buffers + * + * This code was greatly inspired by parts of LibXDiff from Davide Libenzi + * http://www.xmailserver.org/xdiff-lib.html + * + * Rewritten for GIT by Nicolas Pitre <nico@cam.org>, (C) 2005-2007 + * + * This code is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include "git-compat-util.h" +#include "delta.h" + +/* maximum hash entry list for the same hash bucket */ +#define HASH_LIMIT 64 + +#define RABIN_SHIFT 23 +#define RABIN_WINDOW 16 + +static const unsigned int T[256] = { + 0x00000000, 0xab59b4d1, 0x56b369a2, 0xfdeadd73, 0x063f6795, 0xad66d344, + 0x508c0e37, 0xfbd5bae6, 0x0c7ecf2a, 0xa7277bfb, 0x5acda688, 0xf1941259, + 0x0a41a8bf, 0xa1181c6e, 0x5cf2c11d, 0xf7ab75cc, 0x18fd9e54, 0xb3a42a85, + 0x4e4ef7f6, 0xe5174327, 0x1ec2f9c1, 0xb59b4d10, 0x48719063, 0xe32824b2, + 0x1483517e, 0xbfdae5af, 0x423038dc, 0xe9698c0d, 0x12bc36eb, 0xb9e5823a, + 0x440f5f49, 0xef56eb98, 0x31fb3ca8, 0x9aa28879, 0x6748550a, 0xcc11e1db, + 0x37c45b3d, 0x9c9defec, 0x6177329f, 0xca2e864e, 0x3d85f382, 0x96dc4753, + 0x6b369a20, 0xc06f2ef1, 0x3bba9417, 0x90e320c6, 0x6d09fdb5, 0xc6504964, + 0x2906a2fc, 0x825f162d, 0x7fb5cb5e, 0xd4ec7f8f, 0x2f39c569, 0x846071b8, + 0x798aaccb, 0xd2d3181a, 0x25786dd6, 0x8e21d907, 0x73cb0474, 0xd892b0a5, + 0x23470a43, 0x881ebe92, 0x75f463e1, 0xdeadd730, 0x63f67950, 0xc8afcd81, + 0x354510f2, 0x9e1ca423, 0x65c91ec5, 0xce90aa14, 0x337a7767, 0x9823c3b6, + 0x6f88b67a, 0xc4d102ab, 0x393bdfd8, 0x92626b09, 0x69b7d1ef, 0xc2ee653e, + 0x3f04b84d, 0x945d0c9c, 0x7b0be704, 0xd05253d5, 0x2db88ea6, 0x86e13a77, + 0x7d348091, 0xd66d3440, 0x2b87e933, 0x80de5de2, 0x7775282e, 0xdc2c9cff, + 0x21c6418c, 0x8a9ff55d, 0x714a4fbb, 0xda13fb6a, 0x27f92619, 0x8ca092c8, + 0x520d45f8, 0xf954f129, 0x04be2c5a, 0xafe7988b, 0x5432226d, 0xff6b96bc, + 0x02814bcf, 0xa9d8ff1e, 0x5e738ad2, 0xf52a3e03, 0x08c0e370, 0xa39957a1, + 0x584ced47, 0xf3155996, 0x0eff84e5, 0xa5a63034, 0x4af0dbac, 0xe1a96f7d, + 0x1c43b20e, 0xb71a06df, 0x4ccfbc39, 0xe79608e8, 0x1a7cd59b, 0xb125614a, + 0x468e1486, 0xedd7a057, 0x103d7d24, 0xbb64c9f5, 0x40b17313, 0xebe8c7c2, + 0x16021ab1, 0xbd5bae60, 0x6cb54671, 0xc7ecf2a0, 0x3a062fd3, 0x915f9b02, + 0x6a8a21e4, 0xc1d39535, 0x3c394846, 0x9760fc97, 0x60cb895b, 0xcb923d8a, + 0x3678e0f9, 0x9d215428, 0x66f4eece, 0xcdad5a1f, 0x3047876c, 0x9b1e33bd, + 0x7448d825, 0xdf116cf4, 0x22fbb187, 0x89a20556, 0x7277bfb0, 0xd92e0b61, + 0x24c4d612, 0x8f9d62c3, 0x7836170f, 0xd36fa3de, 0x2e857ead, 0x85dcca7c, + 0x7e09709a, 0xd550c44b, 0x28ba1938, 0x83e3ade9, 0x5d4e7ad9, 0xf617ce08, + 0x0bfd137b, 0xa0a4a7aa, 0x5b711d4c, 0xf028a99d, 0x0dc274ee, 0xa69bc03f, + 0x5130b5f3, 0xfa690122, 0x0783dc51, 0xacda6880, 0x570fd266, 0xfc5666b7, + 0x01bcbbc4, 0xaae50f15, 0x45b3e48d, 0xeeea505c, 0x13008d2f, 0xb85939fe, + 0x438c8318, 0xe8d537c9, 0x153feaba, 0xbe665e6b, 0x49cd2ba7, 0xe2949f76, + 0x1f7e4205, 0xb427f6d4, 0x4ff24c32, 0xe4abf8e3, 0x19412590, 0xb2189141, + 0x0f433f21, 0xa41a8bf0, 0x59f05683, 0xf2a9e252, 0x097c58b4, 0xa225ec65, + 0x5fcf3116, 0xf49685c7, 0x033df00b, 0xa86444da, 0x558e99a9, 0xfed72d78, + 0x0502979e, 0xae5b234f, 0x53b1fe3c, 0xf8e84aed, 0x17bea175, 0xbce715a4, + 0x410dc8d7, 0xea547c06, 0x1181c6e0, 0xbad87231, 0x4732af42, 0xec6b1b93, + 0x1bc06e5f, 0xb099da8e, 0x4d7307fd, 0xe62ab32c, 0x1dff09ca, 0xb6a6bd1b, + 0x4b4c6068, 0xe015d4b9, 0x3eb80389, 0x95e1b758, 0x680b6a2b, 0xc352defa, + 0x3887641c, 0x93ded0cd, 0x6e340dbe, 0xc56db96f, 0x32c6cca3, 0x999f7872, + 0x6475a501, 0xcf2c11d0, 0x34f9ab36, 0x9fa01fe7, 0x624ac294, 0xc9137645, + 0x26459ddd, 0x8d1c290c, 0x70f6f47f, 0xdbaf40ae, 0x207afa48, 0x8b234e99, + 0x76c993ea, 0xdd90273b, 0x2a3b52f7, 0x8162e626, 0x7c883b55, 0xd7d18f84, + 0x2c043562, 0x875d81b3, 0x7ab75cc0, 0xd1eee811 +}; + +static const unsigned int U[256] = { + 0x00000000, 0x7eb5200d, 0x5633f4cb, 0x2886d4c6, 0x073e5d47, 0x798b7d4a, + 0x510da98c, 0x2fb88981, 0x0e7cba8e, 0x70c99a83, 0x584f4e45, 0x26fa6e48, + 0x0942e7c9, 0x77f7c7c4, 0x5f711302, 0x21c4330f, 0x1cf9751c, 0x624c5511, + 0x4aca81d7, 0x347fa1da, 0x1bc7285b, 0x65720856, 0x4df4dc90, 0x3341fc9d, + 0x1285cf92, 0x6c30ef9f, 0x44b63b59, 0x3a031b54, 0x15bb92d5, 0x6b0eb2d8, + 0x4388661e, 0x3d3d4613, 0x39f2ea38, 0x4747ca35, 0x6fc11ef3, 0x11743efe, + 0x3eccb77f, 0x40799772, 0x68ff43b4, 0x164a63b9, 0x378e50b6, 0x493b70bb, + 0x61bda47d, 0x1f088470, 0x30b00df1, 0x4e052dfc, 0x6683f93a, 0x1836d937, + 0x250b9f24, 0x5bbebf29, 0x73386bef, 0x0d8d4be2, 0x2235c263, 0x5c80e26e, + 0x740636a8, 0x0ab316a5, 0x2b7725aa, 0x55c205a7, 0x7d44d161, 0x03f1f16c, + 0x2c4978ed, 0x52fc58e0, 0x7a7a8c26, 0x04cfac2b, 0x73e5d470, 0x0d50f47d, + 0x25d620bb, 0x5b6300b6, 0x74db8937, 0x0a6ea93a, 0x22e87dfc, 0x5c5d5df1, + 0x7d996efe, 0x032c4ef3, 0x2baa9a35, 0x551fba38, 0x7aa733b9, 0x041213b4, + 0x2c94c772, 0x5221e77f, 0x6f1ca16c, 0x11a98161, 0x392f55a7, 0x479a75aa, + 0x6822fc2b, 0x1697dc26, 0x3e1108e0, 0x40a428ed, 0x61601be2, 0x1fd53bef, + 0x3753ef29, 0x49e6cf24, 0x665e46a5, 0x18eb66a8, 0x306db26e, 0x4ed89263, + 0x4a173e48, 0x34a21e45, 0x1c24ca83, 0x6291ea8e, 0x4d29630f, 0x339c4302, + 0x1b1a97c4, 0x65afb7c9, 0x446b84c6, 0x3adea4cb, 0x1258700d, 0x6ced5000, + 0x4355d981, 0x3de0f98c, 0x15662d4a, 0x6bd30d47, 0x56ee4b54, 0x285b6b59, + 0x00ddbf9f, 0x7e689f92, 0x51d01613, 0x2f65361e, 0x07e3e2d8, 0x7956c2d5, + 0x5892f1da, 0x2627d1d7, 0x0ea10511, 0x7014251c, 0x5facac9d, 0x21198c90, + 0x099f5856, 0x772a785b, 0x4c921c31, 0x32273c3c, 0x1aa1e8fa, 0x6414c8f7, + 0x4bac4176, 0x3519617b, 0x1d9fb5bd, 0x632a95b0, 0x42eea6bf, 0x3c5b86b2, + 0x14dd5274, 0x6a687279, 0x45d0fbf8, 0x3b65dbf5, 0x13e30f33, 0x6d562f3e, + 0x506b692d, 0x2ede4920, 0x06589de6, 0x78edbdeb, 0x5755346a, 0x29e01467, + 0x0166c0a1, 0x7fd3e0ac, 0x5e17d3a3, 0x20a2f3ae, 0x08242768, 0x76910765, + 0x59298ee4, 0x279caee9, 0x0f1a7a2f, 0x71af5a22, 0x7560f609, 0x0bd5d604, + 0x235302c2, 0x5de622cf, 0x725eab4e, 0x0ceb8b43, 0x246d5f85, 0x5ad87f88, + 0x7b1c4c87, 0x05a96c8a, 0x2d2fb84c, 0x539a9841, 0x7c2211c0, 0x029731cd, + 0x2a11e50b, 0x54a4c506, 0x69998315, 0x172ca318, 0x3faa77de, 0x411f57d3, + 0x6ea7de52, 0x1012fe5f, 0x38942a99, 0x46210a94, 0x67e5399b, 0x19501996, + 0x31d6cd50, 0x4f63ed5d, 0x60db64dc, 0x1e6e44d1, 0x36e89017, 0x485db01a, + 0x3f77c841, 0x41c2e84c, 0x69443c8a, 0x17f11c87, 0x38499506, 0x46fcb50b, + 0x6e7a61cd, 0x10cf41c0, 0x310b72cf, 0x4fbe52c2, 0x67388604, 0x198da609, + 0x36352f88, 0x48800f85, 0x6006db43, 0x1eb3fb4e, 0x238ebd5d, 0x5d3b9d50, + 0x75bd4996, 0x0b08699b, 0x24b0e01a, 0x5a05c017, 0x728314d1, 0x0c3634dc, + 0x2df207d3, 0x534727de, 0x7bc1f318, 0x0574d315, 0x2acc5a94, 0x54797a99, + 0x7cffae5f, 0x024a8e52, 0x06852279, 0x78300274, 0x50b6d6b2, 0x2e03f6bf, + 0x01bb7f3e, 0x7f0e5f33, 0x57888bf5, 0x293dabf8, 0x08f998f7, 0x764cb8fa, + 0x5eca6c3c, 0x207f4c31, 0x0fc7c5b0, 0x7172e5bd, 0x59f4317b, 0x27411176, + 0x1a7c5765, 0x64c97768, 0x4c4fa3ae, 0x32fa83a3, 0x1d420a22, 0x63f72a2f, + 0x4b71fee9, 0x35c4dee4, 0x1400edeb, 0x6ab5cde6, 0x42331920, 0x3c86392d, + 0x133eb0ac, 0x6d8b90a1, 0x450d4467, 0x3bb8646a +}; + +struct index_entry { + const unsigned char *ptr; + unsigned int val; +}; + +struct unpacked_index_entry { + struct index_entry entry; + struct unpacked_index_entry *next; +}; + +struct delta_index { + unsigned long memsize; + const void *src_buf; + unsigned long src_size; + unsigned int hash_mask; + struct index_entry *hash[FLEX_ARRAY]; +}; + +struct delta_index * create_delta_index(const void *buf, unsigned long bufsize) +{ + unsigned int i, hsize, hmask, entries, prev_val, *hash_count; + const unsigned char *data, *buffer = buf; + struct delta_index *index; + struct unpacked_index_entry *entry, **hash; + struct index_entry *packed_entry, **packed_hash; + void *mem; + unsigned long memsize; + + if (!buf || !bufsize) + return NULL; + + /* Determine index hash size. Note that indexing skips the + first byte to allow for optimizing the Rabin's polynomial + initialization in create_delta(). */ + entries = (bufsize - 1) / RABIN_WINDOW; + hsize = entries / 4; + for (i = 4; (1u << i) < hsize && i < 31; i++); + hsize = 1 << i; + hmask = hsize - 1; + + /* allocate lookup index */ + memsize = sizeof(*hash) * hsize + + sizeof(*entry) * entries; + mem = malloc(memsize); + if (!mem) + return NULL; + hash = mem; + mem = hash + hsize; + entry = mem; + + memset(hash, 0, hsize * sizeof(*hash)); + + /* allocate an array to count hash entries */ + hash_count = calloc(hsize, sizeof(*hash_count)); + if (!hash_count) { + free(hash); + return NULL; + } + + /* then populate the index */ + prev_val = ~0; + for (data = buffer + entries * RABIN_WINDOW - RABIN_WINDOW; + data >= buffer; + data -= RABIN_WINDOW) { + unsigned int val = 0; + for (i = 1; i <= RABIN_WINDOW; i++) + val = ((val << 8) | data[i]) ^ T[val >> RABIN_SHIFT]; + if (val == prev_val) { + /* keep the lowest of consecutive identical blocks */ + entry[-1].entry.ptr = data + RABIN_WINDOW; + --entries; + } else { + prev_val = val; + i = val & hmask; + entry->entry.ptr = data + RABIN_WINDOW; + entry->entry.val = val; + entry->next = hash[i]; + hash[i] = entry++; + hash_count[i]++; + } + } + + /* + * Determine a limit on the number of entries in the same hash + * bucket. This guards us against pathological data sets causing + * really bad hash distribution with most entries in the same hash + * bucket that would bring us to O(m*n) computing costs (m and n + * corresponding to reference and target buffer sizes). + * + * Make sure none of the hash buckets has more entries than + * we're willing to test. Otherwise we cull the entry list + * uniformly to still preserve a good repartition across + * the reference buffer. + */ + for (i = 0; i < hsize; i++) { + int acc; + + if (hash_count[i] <= HASH_LIMIT) + continue; + + /* We leave exactly HASH_LIMIT entries in the bucket */ + entries -= hash_count[i] - HASH_LIMIT; + + entry = hash[i]; + acc = 0; + + /* + * Assume that this loop is gone through exactly + * HASH_LIMIT times and is entered and left with + * acc==0. So the first statement in the loop + * contributes (hash_count[i]-HASH_LIMIT)*HASH_LIMIT + * to the accumulator, and the inner loop consequently + * is run (hash_count[i]-HASH_LIMIT) times, removing + * one element from the list each time. Since acc + * balances out to 0 at the final run, the inner loop + * body can't be left with entry==NULL. So we indeed + * encounter entry==NULL in the outer loop only. + */ + do { + acc += hash_count[i] - HASH_LIMIT; + if (acc > 0) { + struct unpacked_index_entry *keep = entry; + do { + entry = entry->next; + acc -= HASH_LIMIT; + } while (acc > 0); + keep->next = entry->next; + } + entry = entry->next; + } while (entry); + } + free(hash_count); + + /* + * Now create the packed index in array form + * rather than linked lists. + */ + memsize = sizeof(*index) + + sizeof(*packed_hash) * (hsize+1) + + sizeof(*packed_entry) * entries; + mem = malloc(memsize); + if (!mem) { + free(hash); + return NULL; + } + + index = mem; + index->memsize = memsize; + index->src_buf = buf; + index->src_size = bufsize; + index->hash_mask = hmask; + + mem = index->hash; + packed_hash = mem; + mem = packed_hash + (hsize+1); + packed_entry = mem; + + for (i = 0; i < hsize; i++) { + /* + * Coalesce all entries belonging to one linked list + * into consecutive array entries. + */ + packed_hash[i] = packed_entry; + for (entry = hash[i]; entry; entry = entry->next) + *packed_entry++ = entry->entry; + } + + /* Sentinel value to indicate the length of the last hash bucket */ + packed_hash[hsize] = packed_entry; + + assert(packed_entry - (struct index_entry *)mem == entries); + free(hash); + + return index; +} + +void free_delta_index(struct delta_index *index) +{ + free(index); +} + +unsigned long sizeof_delta_index(struct delta_index *index) +{ + if (index) + return index->memsize; + else + return 0; +} + +/* + * The maximum size for any opcode sequence, including the initial header + * plus Rabin window plus biggest copy. + */ +#define MAX_OP_SIZE (5 + 5 + 1 + RABIN_WINDOW + 7) + +void * +create_delta(const struct delta_index *index, + const void *trg_buf, unsigned long trg_size, + unsigned long *delta_size, unsigned long max_size) +{ + unsigned int i, outpos, outsize, moff, msize, val; + int inscnt; + const unsigned char *ref_data, *ref_top, *data, *top; + unsigned char *out; + + if (!trg_buf || !trg_size) + return NULL; + + outpos = 0; + outsize = 8192; + if (max_size && outsize >= max_size) + outsize = max_size + MAX_OP_SIZE + 1; + out = malloc(outsize); + if (!out) + return NULL; + + /* store reference buffer size */ + i = index->src_size; + while (i >= 0x80) { + out[outpos++] = i | 0x80; + i >>= 7; + } + out[outpos++] = i; + + /* store target buffer size */ + i = trg_size; + while (i >= 0x80) { + out[outpos++] = i | 0x80; + i >>= 7; + } + out[outpos++] = i; + + ref_data = index->src_buf; + ref_top = ref_data + index->src_size; + data = trg_buf; + top = (const unsigned char *) trg_buf + trg_size; + + outpos++; + val = 0; + for (i = 0; i < RABIN_WINDOW && data < top; i++, data++) { + out[outpos++] = *data; + val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT]; + } + inscnt = i; + + moff = 0; + msize = 0; + while (data < top) { + if (msize < 4096) { + struct index_entry *entry; + val ^= U[data[-RABIN_WINDOW]]; + val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT]; + i = val & index->hash_mask; + for (entry = index->hash[i]; entry < index->hash[i+1]; entry++) { + const unsigned char *ref = entry->ptr; + const unsigned char *src = data; + unsigned int ref_size = ref_top - ref; + if (entry->val != val) + continue; + if (ref_size > top - src) + ref_size = top - src; + if (ref_size <= msize) + break; + while (ref_size-- && *src++ == *ref) + ref++; + if (msize < ref - entry->ptr) { + /* this is our best match so far */ + msize = ref - entry->ptr; + moff = entry->ptr - ref_data; + if (msize >= 4096) /* good enough */ + break; + } + } + } + + if (msize < 4) { + if (!inscnt) + outpos++; + out[outpos++] = *data++; + inscnt++; + if (inscnt == 0x7f) { + out[outpos - inscnt - 1] = inscnt; + inscnt = 0; + } + msize = 0; + } else { + unsigned int left; + unsigned char *op; + + if (inscnt) { + while (moff && ref_data[moff-1] == data[-1]) { + /* we can match one byte back */ + msize++; + moff--; + data--; + outpos--; + if (--inscnt) + continue; + outpos--; /* remove count slot */ + inscnt--; /* make it -1 */ + break; + } + out[outpos - inscnt - 1] = inscnt; + inscnt = 0; + } + + /* A copy op is currently limited to 64KB (pack v2) */ + left = (msize < 0x10000) ? 0 : (msize - 0x10000); + msize -= left; + + op = out + outpos++; + i = 0x80; + + if (moff & 0x000000ff) + out[outpos++] = moff >> 0, i |= 0x01; + if (moff & 0x0000ff00) + out[outpos++] = moff >> 8, i |= 0x02; + if (moff & 0x00ff0000) + out[outpos++] = moff >> 16, i |= 0x04; + if (moff & 0xff000000) + out[outpos++] = moff >> 24, i |= 0x08; + + if (msize & 0x00ff) + out[outpos++] = msize >> 0, i |= 0x10; + if (msize & 0xff00) + out[outpos++] = msize >> 8, i |= 0x20; + + *op = i; + + data += msize; + moff += msize; + msize = left; + + if (msize < 4096) { + int j; + val = 0; + for (j = -RABIN_WINDOW; j < 0; j++) + val = ((val << 8) | data[j]) + ^ T[val >> RABIN_SHIFT]; + } + } + + if (outpos >= outsize - MAX_OP_SIZE) { + void *tmp = out; + outsize = outsize * 3 / 2; + if (max_size && outsize >= max_size) + outsize = max_size + MAX_OP_SIZE + 1; + if (max_size && outpos > max_size) + break; + out = realloc(out, outsize); + if (!out) { + free(tmp); + return NULL; + } + } + } + + if (inscnt) + out[outpos - inscnt - 1] = inscnt; + + if (max_size && outpos > max_size) { + free(out); + return NULL; + } + + *delta_size = outpos; + return out; +} |