/* * 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 , (C) 2005-2007 * Adapted for Bazaar by John Arbash Meinel (C) 2009 * * 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 2 of the License, or * (at your option) any later version. * * NB: The version in GIT is 'version 2 of the Licence only', however Nicolas * has granted permission for use under 'version 2 or later' in private email * to Robert Collins and Karl Fogel on the 6th April 2009. */ #include #include "delta.h" #include #include #include /* maximum hash entry list for the same hash bucket */ #define HASH_LIMIT 64 #define RABIN_SHIFT 23 #define RABIN_WINDOW 16 /* The hash map is sized to put 4 entries per bucket, this gives us ~even room * for more data. Tweaking this number above 4 doesn't seem to help much, * anyway. */ #define EXTRA_NULLS 4 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; const struct source_info *src; unsigned int val; }; struct index_entry_linked_list { struct index_entry *p_entry; struct index_entry_linked_list *next; }; struct unpacked_index_entry { struct index_entry entry; struct unpacked_index_entry *next; }; struct delta_index { unsigned long memsize; /* Total bytes pointed to by this index */ const struct source_info *last_src; /* Information about the referenced source */ unsigned int hash_mask; /* val & hash_mask gives the hash index for a given entry */ unsigned int num_entries; /* The total number of entries in this index */ struct index_entry *last_entry; /* Pointer to the last valid entry */ struct index_entry *hash[]; }; static unsigned int limit_hash_buckets(struct unpacked_index_entry **hash, unsigned int *hash_count, unsigned int hsize, unsigned int entries) { struct unpacked_index_entry *entry; unsigned int 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); } return entries; } static struct delta_index * pack_delta_index(struct unpacked_index_entry **hash, unsigned int hsize, unsigned int num_entries, struct delta_index *old_index) { unsigned int i, j, hmask, memsize, fit_in_old, copied_count; struct unpacked_index_entry *entry; struct delta_index *index; struct index_entry *packed_entry, **packed_hash, *old_entry, *copy_from; struct index_entry null_entry = {0}; void *mem; hmask = hsize - 1; // if (old_index) { // fprintf(stderr, "Packing %d entries into %d for total of %d entries" // " %x => %x\n", // num_entries - old_index->num_entries, // old_index->num_entries, num_entries, // old_index->hash_mask, hmask); // } else { // fprintf(stderr, "Packing %d entries into a new index\n", // num_entries); // } /* First, see if we can squeeze the new items into the existing structure. */ fit_in_old = 0; copied_count = 0; if (old_index && old_index->hash_mask == hmask) { fit_in_old = 1; for (i = 0; i < hsize; ++i) { packed_entry = NULL; for (entry = hash[i]; entry; entry = entry->next) { if (packed_entry == NULL) { /* Find the last open spot */ packed_entry = old_index->hash[i + 1]; --packed_entry; while (packed_entry >= old_index->hash[i] && packed_entry->ptr == NULL) { --packed_entry; } ++packed_entry; } if (packed_entry >= old_index->hash[i+1] || packed_entry->ptr != NULL) { /* There are no free spots here :( */ fit_in_old = 0; break; } /* We found an empty spot to put this entry * Copy it over, and remove it from the linked list, just in * case we end up running out of room later. */ *packed_entry++ = entry->entry; assert(entry == hash[i]); hash[i] = entry->next; copied_count += 1; old_index->num_entries++; } if (!fit_in_old) { break; } } } if (old_index) { if (fit_in_old) { // fprintf(stderr, "Fit all %d entries into old index\n", // copied_count); /* No need to allocate a new buffer */ return NULL; } else { // fprintf(stderr, "Fit only %d entries into old index," // " reallocating\n", copied_count); } } /* * Now create the packed index in array form * rather than linked lists. * Leave a 2-entry gap for inserting more entries between the groups */ memsize = sizeof(*index) + sizeof(*packed_hash) * (hsize+1) + sizeof(*packed_entry) * (num_entries + hsize * EXTRA_NULLS); mem = malloc(memsize); if (!mem) { return NULL; } index = mem; index->memsize = memsize; index->hash_mask = hmask; index->num_entries = num_entries; if (old_index) { if (hmask < old_index->hash_mask) { fprintf(stderr, "hash mask was shrunk %x => %x\n", old_index->hash_mask, hmask); } assert(hmask >= old_index->hash_mask); } 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; /* Old comes earlier as a source, so it always comes first in a given * hash bucket. */ if (old_index) { /* Could we optimize this to use memcpy when hmask == * old_index->hash_mask? Would it make any real difference? */ j = i & old_index->hash_mask; copy_from = old_index->hash[j]; for (old_entry = old_index->hash[j]; old_entry < old_index->hash[j + 1] && old_entry->ptr != NULL; old_entry++) { if ((old_entry->val & hmask) == i) { *packed_entry++ = *old_entry; } } } for (entry = hash[i]; entry; entry = entry->next) { *packed_entry++ = entry->entry; } /* TODO: At this point packed_entry - packed_hash[i] is the number of * records that we have inserted into this hash bucket. * We should *really* consider doing some limiting along the * lines of limit_hash_buckets() to avoid pathological behavior. */ /* Now add extra 'NULL' entries that we can use for future expansion. */ for (j = 0; j < EXTRA_NULLS; ++j ) { *packed_entry++ = null_entry; } } /* Sentinel value to indicate the length of the last hash bucket */ packed_hash[hsize] = packed_entry; if (packed_entry - (struct index_entry *)mem != num_entries + hsize*EXTRA_NULLS) { fprintf(stderr, "We expected %d entries, but created %d\n", num_entries + hsize*EXTRA_NULLS, (int)(packed_entry - (struct index_entry*)mem)); } assert(packed_entry - (struct index_entry *)mem == num_entries + hsize*EXTRA_NULLS); index->last_entry = (packed_entry - 1); return index; } struct delta_index * create_delta_index(const struct source_info *src, struct delta_index *old) { unsigned int i, hsize, hmask, num_entries, prev_val, *hash_count; unsigned int total_num_entries; const unsigned char *data, *buffer; struct delta_index *index; struct unpacked_index_entry *entry, **hash; void *mem; unsigned long memsize; if (!src->buf || !src->size) return NULL; buffer = src->buf; /* Determine index hash size. Note that indexing skips the first byte to allow for optimizing the Rabin's polynomial initialization in create_delta(). */ num_entries = (src->size - 1) / RABIN_WINDOW; if (old != NULL) total_num_entries = num_entries + old->num_entries; else total_num_entries = num_entries; hsize = total_num_entries / 4; for (i = 4; (1u << i) < hsize && i < 31; i++); hsize = 1 << i; hmask = hsize - 1; if (old && old->hash_mask > hmask) { hmask = old->hash_mask; hsize = hmask + 1; } /* allocate lookup index */ memsize = sizeof(*hash) * hsize + sizeof(*entry) * total_num_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 num_entries */ hash_count = calloc(hsize, sizeof(*hash_count)); if (!hash_count) { free(hash); return NULL; } /* then populate the index for the new data */ prev_val = ~0; for (data = buffer + num_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; --num_entries; --total_num_entries; } else { prev_val = val; i = val & hmask; entry->entry.ptr = data + RABIN_WINDOW; entry->entry.val = val; entry->entry.src = src; entry->next = hash[i]; hash[i] = entry++; hash_count[i]++; } } /* TODO: It would be nice to limit_hash_buckets at a better time. */ total_num_entries = limit_hash_buckets(hash, hash_count, hsize, total_num_entries); free(hash_count); if (old) { old->last_src = src; } index = pack_delta_index(hash, hsize, total_num_entries, old); free(hash); if (!index) { return NULL; } index->last_src = src; return index; } /* Take some entries, and put them into a custom hash. * @param entries A list of entries, sorted by position in file * @param num_entries Length of entries * @param out_hsize The maximum size of the hash, the final size will be * returned here */ struct index_entry_linked_list ** _put_entries_into_hash(struct index_entry *entries, unsigned int num_entries, unsigned int hsize) { unsigned int hash_offset, hmask, memsize; struct index_entry *entry, *last_entry; struct index_entry_linked_list *out_entry, **hash; void *mem; hmask = hsize - 1; memsize = sizeof(*hash) * hsize + sizeof(*out_entry) * num_entries; mem = malloc(memsize); if (!mem) return NULL; hash = mem; mem = hash + hsize; out_entry = mem; memset(hash, 0, sizeof(*hash)*(hsize+1)); /* We know that entries are in the order we want in the output, but they * aren't "grouped" by hash bucket yet. */ last_entry = entries + num_entries; for (entry = entries + num_entries - 1; entry >= entries; --entry) { hash_offset = entry->val & hmask; out_entry->p_entry = entry; out_entry->next = hash[hash_offset]; /* TODO: Remove entries that have identical vals, or at least filter * the map a little bit. * if (hash[i] != NULL) { * } */ hash[hash_offset] = out_entry; ++out_entry; } return hash; } struct delta_index * create_index_from_old_and_new_entries(const struct delta_index *old_index, struct index_entry *entries, unsigned int num_entries) { unsigned int i, j, hsize, hmask, total_num_entries; struct delta_index *index; struct index_entry *entry, *packed_entry, **packed_hash; struct index_entry *last_entry, null_entry = {0}; void *mem; unsigned long memsize; struct index_entry_linked_list *unpacked_entry, **mini_hash; /* Determine index hash size. Note that indexing skips the first byte to allow for optimizing the Rabin's polynomial initialization in create_delta(). */ total_num_entries = num_entries + old_index->num_entries; hsize = total_num_entries / 4; for (i = 4; (1u << i) < hsize && i < 31; i++); hsize = 1 << i; if (hsize < old_index->hash_mask) { /* For some reason, there was a code path that would actually *shrink* * the hash size. This screws with some later code, and in general, I * think it better to make the hash bigger, rather than smaller. So * we'll just force the size here. * Possibly done by create_delta_index running into a * limit_hash_buckets call, that ended up transitioning across a * power-of-2. The cause isn't 100% clear, though. */ hsize = old_index->hash_mask + 1; } hmask = hsize - 1; // fprintf(stderr, "resizing index to insert %d entries into array" // " with %d entries: %x => %x\n", // num_entries, old_index->num_entries, old_index->hash_mask, hmask); memsize = sizeof(*index) + sizeof(*packed_hash) * (hsize+1) + sizeof(*packed_entry) * (total_num_entries + hsize*EXTRA_NULLS); mem = malloc(memsize); if (!mem) { return NULL; } index = mem; index->memsize = memsize; index->hash_mask = hmask; index->num_entries = total_num_entries; index->last_src = old_index->last_src; mem = index->hash; packed_hash = mem; mem = packed_hash + (hsize+1); packed_entry = mem; mini_hash = _put_entries_into_hash(entries, num_entries, hsize); if (mini_hash == NULL) { free(index); return NULL; } last_entry = entries + num_entries; for (i = 0; i < hsize; i++) { /* * Coalesce all entries belonging in one hash bucket * into consecutive array entries. * The entries in old_index all come before 'entries'. */ packed_hash[i] = packed_entry; /* Copy any of the old entries across */ /* Would we rather use memcpy? */ if (hmask == old_index->hash_mask) { for (entry = old_index->hash[i]; entry < old_index->hash[i+1] && entry->ptr != NULL; ++entry) { assert((entry->val & hmask) == i); *packed_entry++ = *entry; } } else { /* If we resized the index from this action, all of the old values * will be found in the previous location, but they will end up * spread across the new locations. */ j = i & old_index->hash_mask; for (entry = old_index->hash[j]; entry < old_index->hash[j+1] && entry->ptr != NULL; ++entry) { assert((entry->val & old_index->hash_mask) == j); if ((entry->val & hmask) == i) { /* Any entries not picked up here will be picked up on the * next pass. */ *packed_entry++ = *entry; } } } /* Now see if we need to insert any of the new entries. * Note that loop ends up O(hsize*num_entries), so we expect that * num_entries is always small. * We also help a little bit by collapsing the entry range when the * endpoints are inserted. However, an alternative would be to build a * quick hash lookup for just the new entries. * Testing shows that this list can easily get up to about 100 * entries, the tradeoff is a malloc, 1 pass over the entries, copying * them into a sorted buffer, and a free() when done, */ for (unpacked_entry = mini_hash[i]; unpacked_entry; unpacked_entry = unpacked_entry->next) { assert((unpacked_entry->p_entry->val & hmask) == i); *packed_entry++ = *(unpacked_entry->p_entry); } /* Now insert some extra nulls */ for (j = 0; j < EXTRA_NULLS; ++j) { *packed_entry++ = null_entry; } } free(mini_hash); /* Sentinel value to indicate the length of the last hash bucket */ packed_hash[hsize] = packed_entry; if ((packed_entry - (struct index_entry *)mem) != (total_num_entries + hsize*EXTRA_NULLS)) { fprintf(stderr, "We expected %d entries, but created %d\n", total_num_entries + hsize*EXTRA_NULLS, (int)(packed_entry - (struct index_entry*)mem)); fflush(stderr); } assert((packed_entry - (struct index_entry *)mem) == (total_num_entries + hsize * EXTRA_NULLS)); index->last_entry = (packed_entry - 1); return index; } void get_text(char buff[128], const unsigned char *ptr) { unsigned int i; const unsigned char *start; unsigned char cmd; start = (ptr-RABIN_WINDOW-1); cmd = *(start); if (cmd < 0x80) {// This is likely to be an insert instruction if (cmd < RABIN_WINDOW) { cmd = RABIN_WINDOW; } } else { /* This was either a copy [should never be] or it * was a longer insert so the insert start happened at 16 more * bytes back. */ cmd = RABIN_WINDOW + 1; } if (cmd > 60) { cmd = 60; /* Be friendly to 80char terms */ } /* Copy the 1 byte command, and 4 bytes after the insert */ cmd += 5; memcpy(buff, start, cmd); buff[cmd] = 0; for (i = 0; i < cmd; ++i) { if (buff[i] == '\n') { buff[i] = 'N'; } else if (buff[i] == '\t') { buff[i] = 'T'; } } } struct delta_index * create_delta_index_from_delta(const struct source_info *src, struct delta_index *old_index) { unsigned int i, num_entries, max_num_entries, prev_val, num_inserted; unsigned int hash_offset; const unsigned char *data, *buffer, *top; unsigned char cmd; struct delta_index *new_index; struct index_entry *entry, *entries; if (!src->buf || !src->size) return NULL; buffer = src->buf; top = buffer + src->size; /* Determine index hash size. Note that indexing skips the first byte to allow for optimizing the Rabin's polynomial initialization in create_delta(). This computes the maximum number of entries that could be held. The actual number will be recomputed during processing. */ max_num_entries = (src->size - 1) / RABIN_WINDOW; /* allocate an array to hold whatever entries we find */ entries = malloc(sizeof(*entry) * max_num_entries); if (!entries) /* malloc failure */ return NULL; /* then populate the index for the new data */ prev_val = ~0; data = buffer; /* target size */ /* get_delta_hdr_size doesn't mutate the content, just moves the * start-of-data pointer, so it is safe to do the cast. */ get_delta_hdr_size((unsigned char**)&data, top); entry = entries; /* start at the first slot */ num_entries = 0; /* calculate the real number of entries */ while (data < top) { cmd = *data++; if (cmd & 0x80) { /* Copy instruction, skip it */ if (cmd & 0x01) data++; if (cmd & 0x02) data++; if (cmd & 0x04) data++; if (cmd & 0x08) data++; if (cmd & 0x10) data++; if (cmd & 0x20) data++; if (cmd & 0x40) data++; } else if (cmd) { /* Insert instruction, we want to index these bytes */ if (data + cmd > top) { /* Invalid insert, not enough bytes in the delta */ break; } /* The create_delta code requires a match at least 4 characters * (including only the last char of the RABIN_WINDOW) before it * will consider it something worth copying rather than inserting. * So we don't want to index anything that we know won't ever be a * match. */ for (; cmd > RABIN_WINDOW + 3; cmd -= RABIN_WINDOW, 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) { /* Only keep the first of consecutive data */ prev_val = val; num_entries++; entry->ptr = data + RABIN_WINDOW; entry->val = val; entry->src = src; entry++; if (num_entries > max_num_entries) { /* We ran out of entry room, something is really wrong */ break; } } } /* Move the data pointer by whatever remainder is left */ data += cmd; } else { /* * cmd == 0 is reserved for future encoding * extensions. In the mean time we must fail when * encountering them (might be data corruption). */ break; } } if (data != top) { /* Something was wrong with this delta */ free(entries); return NULL; } if (num_entries == 0) { /** Nothing to index **/ free(entries); return NULL; } assert(old_index != NULL); old_index->last_src = src; /* See if we can fill in these values into the holes in the array */ entry = entries; num_inserted = 0; for (; num_entries > 0; --num_entries, ++entry) { struct index_entry *next_bucket_entry, *cur_entry, *bucket_first_entry; hash_offset = (entry->val & old_index->hash_mask); /* The basic structure is a hash => packed_entries that fit in that * hash bucket. Things are structured such that the hash-pointers are * strictly ordered. So we start by pointing to the next pointer, and * walk back until we stop getting NULL targets, and then go back * forward. If there are no NULL targets, then we know because * entry->ptr will not be NULL. */ // The start of the next bucket, this may point past the end of the // entry table if hash_offset is the last bucket. next_bucket_entry = old_index->hash[hash_offset + 1]; // First entry in this bucket bucket_first_entry = old_index->hash[hash_offset]; cur_entry = next_bucket_entry - 1; while (cur_entry->ptr == NULL && cur_entry >= bucket_first_entry) { cur_entry--; } // cur_entry now either points at the first NULL, or it points to // next_bucket_entry if there were no blank spots. cur_entry++; if (cur_entry >= next_bucket_entry || cur_entry->ptr != NULL) { /* There is no room for this entry, we have to resize */ // char buff[128]; // get_text(buff, entry->ptr); // fprintf(stderr, "Failed to find an opening @%x for %8x:\n '%s'\n", // hash_offset, entry->val, buff); // for (old_entry = old_index->hash[hash_offset]; // old_entry < old_index->hash[hash_offset+1]; // ++old_entry) { // get_text(buff, old_entry->ptr); // fprintf(stderr, " [%2d] %8x %8x: '%s'\n", // (int)(old_entry - old_index->hash[hash_offset]), // old_entry->val, old_entry->ptr, buff); // } break; } num_inserted++; *cur_entry = *entry; /* For entries which we *do* manage to insert into old_index, we don't * want them double copied into the final output. */ old_index->num_entries++; } if (num_entries > 0) { /* We couldn't fit the new entries into the old index, so allocate a * new one, and fill it with stuff. */ // fprintf(stderr, "inserted %d before resize\n", num_inserted); new_index = create_index_from_old_and_new_entries(old_index, entry, num_entries); } else { new_index = NULL; // fprintf(stderr, "inserted %d without resizing\n", num_inserted); } free(entries); return new_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; const struct source_info *msource; int inscnt; const unsigned char *ref_data, *ref_top, *data, *top; unsigned char *out; unsigned long source_size; if (!trg_buf || !trg_size) return NULL; if (index == NULL) 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; source_size = index->last_src->size + index->last_src->agg_offset; /* store target buffer size */ i = trg_size; while (i >= 0x80) { out[outpos++] = i | 0x80; i >>= 7; } out[outpos++] = i; data = trg_buf; top = (const unsigned char *) trg_buf + trg_size; /* Start the matching by filling out with a simple 'insert' instruction, of * the first RABIN_WINDOW bytes of the input. */ outpos++; /* leave a byte for the insert command */ val = 0; for (i = 0; i < RABIN_WINDOW && data < top; i++, data++) { out[outpos++] = *data; val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT]; } /* we are now setup with an insert of 'i' bytes and val contains the RABIN * hash for those bytes, and data points to the RABIN_WINDOW+1 byte of * input. */ inscnt = i; moff = 0; msize = 0; msource = NULL; while (data < top) { if (msize < 4096) { /* we don't have a 'worthy enough' match yet, so let's look for * one. */ struct index_entry *entry; /* Shift the window by one byte. */ val ^= U[data[-RABIN_WINDOW]]; val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT]; i = val & index->hash_mask; /* TODO: When using multiple indexes like this, the hash tables * mapping val => index_entry become less efficient. * You end up getting a lot more collisions in the hash, * which doesn't actually lead to a entry->val match. */ for (entry = index->hash[i]; entry < index->hash[i+1] && entry->src != NULL; entry++) { const unsigned char *ref; const unsigned char *src; unsigned int ref_size; if (entry->val != val) continue; ref = entry->ptr; src = data; ref_data = entry->src->buf; ref_top = ref_data + entry->src->size; ref_size = ref_top - ref; /* ref_size is the longest possible match that we could make * here. If ref_size <= msize, then we know that we cannot * match more bytes with this location that we have already * matched. */ if (ref_size > top - src) ref_size = top - src; if (ref_size <= msize) break; /* See how many bytes actually match at this location. */ while (ref_size-- && *src++ == *ref) ref++; if (msize < ref - entry->ptr) { /* this is our best match so far */ msize = ref - entry->ptr; msource = entry->src; moff = entry->ptr - ref_data; if (msize >= 4096) /* good enough */ break; } } } if (msize < 4) { /* The best match right now is less than 4 bytes long. So just add * the current byte to the insert instruction. Increment the insert * counter, and copy the byte of data into the output buffer. */ if (!inscnt) outpos++; out[outpos++] = *data++; inscnt++; if (inscnt == 0x7f) { /* We have a max length insert instruction, finalize it in the * output. */ out[outpos - inscnt - 1] = inscnt; inscnt = 0; } msize = 0; } else { unsigned int left; unsigned char *op; if (inscnt) { ref_data = msource->buf; 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; /* moff is the offset in the local structure, for encoding, we need * to push it into the global offset */ assert(moff < msource->size); moff += msource->agg_offset; assert(moff + msize <= source_size); 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; /* Put it back into local coordinates, in case we have multiple * copies in a row. */ moff -= msource->agg_offset; 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; } /* vim: et ts=4 sw=4 sts=4 */