diff options
Diffstat (limited to 'bloom.c')
| -rw-r--r-- | bloom.c | 38 |
1 files changed, 37 insertions, 1 deletions
@@ -8,6 +8,11 @@ static uint32_t rotate_left(uint32_t value, int32_t count) return ((value << count) | (value >> ((-count) & mask))); } +static inline unsigned char get_bitmask(uint32_t pos) +{ + return ((unsigned char)1) << (pos & (BITS_PER_WORD - 1)); +} + /* * Calculate the murmur3 32-bit hash value for the given data * using the given seed. @@ -70,4 +75,35 @@ uint32_t murmur3_seeded(uint32_t seed, const char *data, size_t len) seed ^= (seed >> 16); return seed; -}
\ No newline at end of file +} + +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); + } +} |