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-rw-r--r--bloom.c276
1 files changed, 276 insertions, 0 deletions
diff --git a/bloom.c b/bloom.c
new file mode 100644
index 0000000000..dd9bab9bbd
--- /dev/null
+++ b/bloom.c
@@ -0,0 +1,276 @@
+#include "git-compat-util.h"
+#include "bloom.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "revision.h"
+#include "hashmap.h"
+#include "commit-graph.h"
+#include "commit.h"
+
+define_commit_slab(bloom_filter_slab, struct bloom_filter);
+
+struct bloom_filter_slab bloom_filters;
+
+struct pathmap_hash_entry {
+ struct hashmap_entry entry;
+ const char path[FLEX_ARRAY];
+};
+
+static uint32_t rotate_left(uint32_t value, int32_t count)
+{
+ uint32_t mask = 8 * sizeof(uint32_t) - 1;
+ count &= mask;
+ return ((value << count) | (value >> ((-count) & mask)));
+}
+
+static inline unsigned char get_bitmask(uint32_t pos)
+{
+ return ((unsigned char)1) << (pos & (BITS_PER_WORD - 1));
+}
+
+static int load_bloom_filter_from_graph(struct commit_graph *g,
+ struct bloom_filter *filter,
+ struct commit *c)
+{
+ uint32_t lex_pos, start_index, end_index;
+
+ while (c->graph_pos < g->num_commits_in_base)
+ g = g->base_graph;
+
+ /* The commit graph commit 'c' lives in doesn't carry bloom filters. */
+ if (!g->chunk_bloom_indexes)
+ return 0;
+
+ lex_pos = c->graph_pos - g->num_commits_in_base;
+
+ end_index = get_be32(g->chunk_bloom_indexes + 4 * lex_pos);
+
+ if (lex_pos > 0)
+ start_index = get_be32(g->chunk_bloom_indexes + 4 * (lex_pos - 1));
+ else
+ start_index = 0;
+
+ filter->len = end_index - start_index;
+ filter->data = (unsigned char *)(g->chunk_bloom_data +
+ sizeof(unsigned char) * start_index +
+ BLOOMDATA_CHUNK_HEADER_SIZE);
+
+ return 1;
+}
+
+/*
+ * Calculate the murmur3 32-bit hash value for the given data
+ * using the given seed.
+ * Produces a uniformly distributed hash value.
+ * Not considered to be cryptographically secure.
+ * Implemented as described in https://en.wikipedia.org/wiki/MurmurHash#Algorithm
+ */
+uint32_t murmur3_seeded(uint32_t seed, const char *data, size_t len)
+{
+ const uint32_t c1 = 0xcc9e2d51;
+ const uint32_t c2 = 0x1b873593;
+ const uint32_t r1 = 15;
+ const uint32_t r2 = 13;
+ const uint32_t m = 5;
+ const uint32_t n = 0xe6546b64;
+ int i;
+ uint32_t k1 = 0;
+ const char *tail;
+
+ int len4 = len / sizeof(uint32_t);
+
+ uint32_t k;
+ for (i = 0; i < len4; i++) {
+ uint32_t byte1 = (uint32_t)data[4*i];
+ uint32_t byte2 = ((uint32_t)data[4*i + 1]) << 8;
+ uint32_t byte3 = ((uint32_t)data[4*i + 2]) << 16;
+ uint32_t byte4 = ((uint32_t)data[4*i + 3]) << 24;
+ k = byte1 | byte2 | byte3 | byte4;
+ k *= c1;
+ k = rotate_left(k, r1);
+ k *= c2;
+
+ seed ^= k;
+ seed = rotate_left(seed, r2) * m + n;
+ }
+
+ tail = (data + len4 * sizeof(uint32_t));
+
+ switch (len & (sizeof(uint32_t) - 1)) {
+ case 3:
+ k1 ^= ((uint32_t)tail[2]) << 16;
+ /*-fallthrough*/
+ case 2:
+ k1 ^= ((uint32_t)tail[1]) << 8;
+ /*-fallthrough*/
+ case 1:
+ k1 ^= ((uint32_t)tail[0]) << 0;
+ k1 *= c1;
+ k1 = rotate_left(k1, r1);
+ k1 *= c2;
+ seed ^= k1;
+ break;
+ }
+
+ seed ^= (uint32_t)len;
+ seed ^= (seed >> 16);
+ seed *= 0x85ebca6b;
+ seed ^= (seed >> 13);
+ seed *= 0xc2b2ae35;
+ seed ^= (seed >> 16);
+
+ return seed;
+}
+
+void fill_bloom_key(const char *data,
+ size_t len,
+ struct bloom_key *key,
+ const struct bloom_filter_settings *settings)
+{
+ int i;
+ const uint32_t seed0 = 0x293ae76f;
+ const uint32_t seed1 = 0x7e646e2c;
+ const uint32_t hash0 = murmur3_seeded(seed0, data, len);
+ const uint32_t hash1 = murmur3_seeded(seed1, data, len);
+
+ key->hashes = (uint32_t *)xcalloc(settings->num_hashes, sizeof(uint32_t));
+ for (i = 0; i < settings->num_hashes; i++)
+ key->hashes[i] = hash0 + i * hash1;
+}
+
+void add_key_to_filter(const struct bloom_key *key,
+ struct bloom_filter *filter,
+ const struct bloom_filter_settings *settings)
+{
+ int i;
+ uint64_t mod = filter->len * BITS_PER_WORD;
+
+ for (i = 0; i < settings->num_hashes; i++) {
+ uint64_t hash_mod = key->hashes[i] % mod;
+ uint64_t block_pos = hash_mod / BITS_PER_WORD;
+
+ filter->data[block_pos] |= get_bitmask(hash_mod);
+ }
+}
+
+void init_bloom_filters(void)
+{
+ init_bloom_filter_slab(&bloom_filters);
+}
+
+struct bloom_filter *get_bloom_filter(struct repository *r,
+ struct commit *c,
+ int compute_if_not_present)
+{
+ struct bloom_filter *filter;
+ struct bloom_filter_settings settings = DEFAULT_BLOOM_FILTER_SETTINGS;
+ int i;
+ struct diff_options diffopt;
+ int max_changes = 512;
+
+ if (bloom_filters.slab_size == 0)
+ return NULL;
+
+ filter = bloom_filter_slab_at(&bloom_filters, c);
+
+ if (!filter->data) {
+ load_commit_graph_info(r, c);
+ if (c->graph_pos != COMMIT_NOT_FROM_GRAPH &&
+ r->objects->commit_graph->chunk_bloom_indexes) {
+ if (load_bloom_filter_from_graph(r->objects->commit_graph, filter, c))
+ return filter;
+ else
+ return NULL;
+ }
+ }
+
+ if (filter->data || !compute_if_not_present)
+ return filter;
+
+ repo_diff_setup(r, &diffopt);
+ diffopt.flags.recursive = 1;
+ diffopt.detect_rename = 0;
+ diffopt.max_changes = max_changes;
+ diff_setup_done(&diffopt);
+
+ if (c->parents)
+ diff_tree_oid(&c->parents->item->object.oid, &c->object.oid, "", &diffopt);
+ else
+ diff_tree_oid(NULL, &c->object.oid, "", &diffopt);
+ diffcore_std(&diffopt);
+
+ if (diff_queued_diff.nr <= max_changes) {
+ struct hashmap pathmap;
+ struct pathmap_hash_entry *e;
+ struct hashmap_iter iter;
+ hashmap_init(&pathmap, NULL, NULL, 0);
+
+ for (i = 0; i < diff_queued_diff.nr; i++) {
+ const char *path = diff_queued_diff.queue[i]->two->path;
+
+ /*
+ * Add each leading directory of the changed file, i.e. for
+ * 'dir/subdir/file' add 'dir' and 'dir/subdir' as well, so
+ * the Bloom filter could be used to speed up commands like
+ * 'git log dir/subdir', too.
+ *
+ * Note that directories are added without the trailing '/'.
+ */
+ do {
+ char *last_slash = strrchr(path, '/');
+
+ FLEX_ALLOC_STR(e, path, path);
+ hashmap_entry_init(&e->entry, strhash(path));
+ hashmap_add(&pathmap, &e->entry);
+
+ if (!last_slash)
+ last_slash = (char*)path;
+ *last_slash = '\0';
+
+ } while (*path);
+
+ diff_free_filepair(diff_queued_diff.queue[i]);
+ }
+
+ filter->len = (hashmap_get_size(&pathmap) * settings.bits_per_entry + BITS_PER_WORD - 1) / BITS_PER_WORD;
+ filter->data = xcalloc(filter->len, sizeof(unsigned char));
+
+ hashmap_for_each_entry(&pathmap, &iter, e, entry) {
+ struct bloom_key key;
+ fill_bloom_key(e->path, strlen(e->path), &key, &settings);
+ add_key_to_filter(&key, filter, &settings);
+ }
+
+ hashmap_free_entries(&pathmap, struct pathmap_hash_entry, entry);
+ } else {
+ for (i = 0; i < diff_queued_diff.nr; i++)
+ diff_free_filepair(diff_queued_diff.queue[i]);
+ filter->data = NULL;
+ filter->len = 0;
+ }
+
+ free(diff_queued_diff.queue);
+ DIFF_QUEUE_CLEAR(&diff_queued_diff);
+
+ return filter;
+}
+
+int bloom_filter_contains(const struct bloom_filter *filter,
+ const struct bloom_key *key,
+ const struct bloom_filter_settings *settings)
+{
+ int i;
+ uint64_t mod = filter->len * BITS_PER_WORD;
+
+ if (!mod)
+ return -1;
+
+ for (i = 0; i < settings->num_hashes; i++) {
+ uint64_t hash_mod = key->hashes[i] % mod;
+ uint64_t block_pos = hash_mod / BITS_PER_WORD;
+ if (!(filter->data[block_pos] & get_bitmask(hash_mod)))
+ return 0;
+ }
+
+ return 1;
+} \ No newline at end of file