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Merge branch 'jt/binsearch-with-fanout'
Refactor the code to binary search starting from a fan-out table (which is how the packfile is indexed with object names) into a reusable helper. * jt/binsearch-with-fanout: packfile: refactor hash search with fanout table packfile: remove GIT_DEBUG_LOOKUP log statements
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commit
f2fcbeb3bf
29
packfile.c
29
packfile.c
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@ -1722,11 +1722,8 @@ off_t find_pack_entry_one(const unsigned char *sha1,
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{
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const uint32_t *level1_ofs = p->index_data;
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const unsigned char *index = p->index_data;
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unsigned hi, lo, stride;
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static int debug_lookup = -1;
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if (debug_lookup < 0)
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debug_lookup = !!getenv("GIT_DEBUG_LOOKUP");
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unsigned stride;
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uint32_t result;
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if (!index) {
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if (open_pack_index(p))
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@ -1739,8 +1736,6 @@ off_t find_pack_entry_one(const unsigned char *sha1,
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index += 8;
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}
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index += 4 * 256;
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hi = ntohl(level1_ofs[*sha1]);
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lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
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if (p->index_version > 1) {
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stride = 20;
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} else {
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@ -1748,24 +1743,8 @@ off_t find_pack_entry_one(const unsigned char *sha1,
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index += 4;
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}
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if (debug_lookup)
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printf("%02x%02x%02x... lo %u hi %u nr %"PRIu32"\n",
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sha1[0], sha1[1], sha1[2], lo, hi, p->num_objects);
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while (lo < hi) {
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unsigned mi = lo + (hi - lo) / 2;
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int cmp = hashcmp(index + mi * stride, sha1);
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if (debug_lookup)
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printf("lo %u hi %u rg %u mi %u\n",
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lo, hi, hi - lo, mi);
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if (!cmp)
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return nth_packed_object_offset(p, mi);
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if (cmp > 0)
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hi = mi;
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else
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lo = mi+1;
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}
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if (bsearch_hash(sha1, level1_ofs, index, stride, &result))
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return nth_packed_object_offset(p, result);
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return 0;
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}
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@ -99,3 +99,31 @@ int sha1_pos(const unsigned char *sha1, void *table, size_t nr,
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} while (lo < hi);
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return -lo-1;
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}
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int bsearch_hash(const unsigned char *sha1, const uint32_t *fanout_nbo,
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const unsigned char *table, size_t stride, uint32_t *result)
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{
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uint32_t hi, lo;
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hi = ntohl(fanout_nbo[*sha1]);
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lo = ((*sha1 == 0x0) ? 0 : ntohl(fanout_nbo[*sha1 - 1]));
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while (lo < hi) {
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unsigned mi = lo + (hi - lo) / 2;
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int cmp = hashcmp(table + mi * stride, sha1);
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if (!cmp) {
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if (result)
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*result = mi;
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return 1;
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}
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if (cmp > 0)
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hi = mi;
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else
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lo = mi + 1;
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}
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if (result)
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*result = lo;
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return 0;
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}
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@ -7,4 +7,26 @@ extern int sha1_pos(const unsigned char *sha1,
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void *table,
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size_t nr,
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sha1_access_fn fn);
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/*
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* Searches for sha1 in table, using the given fanout table to determine the
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* interval to search, then using binary search. Returns 1 if found, 0 if not.
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*
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* Takes the following parameters:
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*
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* - sha1: the hash to search for
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* - fanout_nbo: a 256-element array of NETWORK-order 32-bit integers; the
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* integer at position i represents the number of elements in table whose
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* first byte is less than or equal to i
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* - table: a sorted list of hashes with optional extra information in between
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* - stride: distance between two consecutive elements in table (should be
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* GIT_MAX_RAWSZ or greater)
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* - result: if not NULL, this function stores the element index of the
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* position found (if the search is successful) or the index of the least
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* element that is greater than sha1 (if the search is not successful)
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*
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* This function does not verify the validity of the fanout table.
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*/
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int bsearch_hash(const unsigned char *sha1, const uint32_t *fanout_nbo,
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const unsigned char *table, size_t stride, uint32_t *result);
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#endif
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