bloom.c - git - Git at Google

 #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);

 static 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;
 	uint32_t graph_pos = commit_graph_position(c);

 	while (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 = 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 clear_bloom_key(struct bloom_key *key)
 {
 	FREE_AND_NULL(key->hashes);
 }

 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);
 }

 static int pathmap_cmp(const void *hashmap_cmp_fn_data,
 		       const struct hashmap_entry *eptr,
 		       const struct hashmap_entry *entry_or_key,
 		       const void *keydata)
 {
 	const struct pathmap_hash_entry *e1, *e2;

 	e1 = container_of(eptr, const struct pathmap_hash_entry, entry);
 	e2 = container_of(entry_or_key, const struct pathmap_hash_entry, entry);

 	return strcmp(e1->path, e2->path);
 }

 static void init_truncated_large_filter(struct bloom_filter *filter)
 {
 	filter->data = xmalloc(1);
 	filter->data[0] = 0xFF;
 	filter->len = 1;
 }

 struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
 						 struct commit *c,
 						 int compute_if_not_present,
 						 const struct bloom_filter_settings *settings,
 						 enum bloom_filter_computed *computed)
 {
 	struct bloom_filter *filter;
 	int i;
 	struct diff_options diffopt;

 	if (computed)
 		*computed = BLOOM_NOT_COMPUTED;

 	if (!bloom_filters.slab_size)
 		return NULL;

 	filter = bloom_filter_slab_at(&bloom_filters, c);

 	if (!filter->data) {
 		load_commit_graph_info(r, c);
 		if (commit_graph_position(c) != COMMIT_NOT_FROM_GRAPH)
 			load_bloom_filter_from_graph(r->objects->commit_graph, filter, c);
 	}

 	if (filter->data && filter->len)
 		return filter;
 	if (!compute_if_not_present)
 		return NULL;

 	repo_diff_setup(r, &diffopt);
 	diffopt.flags.recursive = 1;
 	diffopt.detect_rename = 0;
 	diffopt.max_changes = settings->max_changed_paths;
 	diff_setup_done(&diffopt);

 	/* ensure commit is parsed so we have parent information */
 	repo_parse_commit(r, c);

 	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 <= settings->max_changed_paths) {
 		struct hashmap pathmap = HASHMAP_INIT(pathmap_cmp, NULL);
 		struct pathmap_hash_entry *e;
 		struct hashmap_iter iter;

 		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));

 				if (!hashmap_get(&pathmap, &e->entry, NULL))
 					hashmap_add(&pathmap, &e->entry);
 				else
 					free(e);

 				if (!last_slash)
 					last_slash = (char*)path;
 				*last_slash = '\0';

 			} while (*path);

 			diff_free_filepair(diff_queued_diff.queue[i]);
 		}

 		if (hashmap_get_size(&pathmap) > settings->max_changed_paths) {
 			init_truncated_large_filter(filter);
 			if (computed)
 				*computed |= BLOOM_TRUNC_LARGE;
 			goto cleanup;
 		}

 		filter->len = (hashmap_get_size(&pathmap) * settings->bits_per_entry + BITS_PER_WORD - 1) / BITS_PER_WORD;
 		if (!filter->len) {
 			if (computed)
 				*computed |= BLOOM_TRUNC_EMPTY;
 			filter->len = 1;
 		}
 		CALLOC_ARRAY(filter->data, filter->len);

 		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);
 			clear_bloom_key(&key);
 		}

 	cleanup:
 		hashmap_clear_and_free(&pathmap, struct pathmap_hash_entry, entry);
 	} else {
 		for (i = 0; i < diff_queued_diff.nr; i++)
 			diff_free_filepair(diff_queued_diff.queue[i]);
 		init_truncated_large_filter(filter);

 		if (computed)
 			*computed |= BLOOM_TRUNC_LARGE;
 	}

 	if (computed)
 		*computed |= BLOOM_COMPUTED;

 	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;
 }
	#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);

	static 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;
	uint32_t graph_pos = commit_graph_position(c);

	while (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 = 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 clear_bloom_key(struct bloom_key *key)
	{
	FREE_AND_NULL(key->hashes);
	}

	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);
	}

	static int pathmap_cmp(const void *hashmap_cmp_fn_data,
	const struct hashmap_entry *eptr,
	const struct hashmap_entry *entry_or_key,
	const void *keydata)
	{
	const struct pathmap_hash_entry e1, e2;

	e1 = container_of(eptr, const struct pathmap_hash_entry, entry);
	e2 = container_of(entry_or_key, const struct pathmap_hash_entry, entry);

	return strcmp(e1->path, e2->path);
	}

	static void init_truncated_large_filter(struct bloom_filter *filter)
	{
	filter->data = xmalloc(1);
	filter->data[0] = 0xFF;
	filter->len = 1;
	}

	struct bloom_filter get_or_compute_bloom_filter(struct repository r,
	struct commit *c,
	int compute_if_not_present,
	const struct bloom_filter_settings *settings,
	enum bloom_filter_computed *computed)
	{
	struct bloom_filter *filter;
	int i;
	struct diff_options diffopt;

	if (computed)
	*computed = BLOOM_NOT_COMPUTED;

	if (!bloom_filters.slab_size)
	return NULL;

	filter = bloom_filter_slab_at(&bloom_filters, c);

	if (!filter->data) {
	load_commit_graph_info(r, c);
	if (commit_graph_position(c) != COMMIT_NOT_FROM_GRAPH)
	load_bloom_filter_from_graph(r->objects->commit_graph, filter, c);
	}

	if (filter->data && filter->len)
	return filter;
	if (!compute_if_not_present)
	return NULL;

	repo_diff_setup(r, &diffopt);
	diffopt.flags.recursive = 1;
	diffopt.detect_rename = 0;
	diffopt.max_changes = settings->max_changed_paths;
	diff_setup_done(&diffopt);

	/* ensure commit is parsed so we have parent information */
	repo_parse_commit(r, c);

	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 <= settings->max_changed_paths) {
	struct hashmap pathmap = HASHMAP_INIT(pathmap_cmp, NULL);
	struct pathmap_hash_entry *e;
	struct hashmap_iter iter;

	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));

	if (!hashmap_get(&pathmap, &e->entry, NULL))
	hashmap_add(&pathmap, &e->entry);
	else
	free(e);

	if (!last_slash)
	last_slash = (char*)path;
	*last_slash = '\0';

	} while (*path);

	diff_free_filepair(diff_queued_diff.queue[i]);
	}

	if (hashmap_get_size(&pathmap) > settings->max_changed_paths) {
	init_truncated_large_filter(filter);
	if (computed)
	*computed \|= BLOOM_TRUNC_LARGE;
	goto cleanup;
	}

	filter->len = (hashmap_get_size(&pathmap) * settings->bits_per_entry + BITS_PER_WORD - 1) / BITS_PER_WORD;
	if (!filter->len) {
	if (computed)
	*computed \|= BLOOM_TRUNC_EMPTY;
	filter->len = 1;
	}
	CALLOC_ARRAY(filter->data, filter->len);

	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);
	clear_bloom_key(&key);
	}

	cleanup:
	hashmap_clear_and_free(&pathmap, struct pathmap_hash_entry, entry);
	} else {
	for (i = 0; i < diff_queued_diff.nr; i++)
	diff_free_filepair(diff_queued_diff.queue[i]);
	init_truncated_large_filter(filter);

	if (computed)
	*computed \|= BLOOM_TRUNC_LARGE;
	}

	if (computed)
	*computed \|= BLOOM_COMPUTED;

	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;
	}