diff options
Diffstat (limited to 'source/blender/blenlib/intern/hash_mm2a.c')
| -rw-r--r-- | source/blender/blenlib/intern/hash_mm2a.c | 44 |
1 files changed, 41 insertions, 3 deletions
diff --git a/source/blender/blenlib/intern/hash_mm2a.c b/source/blender/blenlib/intern/hash_mm2a.c index 8b4242fa5be..80c92e735c1 100644 --- a/source/blender/blenlib/intern/hash_mm2a.c +++ b/source/blender/blenlib/intern/hash_mm2a.c @@ -49,6 +49,13 @@ (h) = ((h) * MM2A_M) ^ (k); \ } (void)0 +#define MM2A_MIX_FINALIZE(h) \ +{ \ + (h) ^= (h) >> 13; \ + (h) *= MM2A_M; \ + (h) ^= (h) >> 15; \ +} (void)0 + static void mm2a_mix_tail(BLI_HashMurmur2A *mm2, const unsigned char **data, size_t *len) { while (*len && ((*len < 4) || mm2->count)) { @@ -99,9 +106,40 @@ uint32_t BLI_hash_mm2a_end(BLI_HashMurmur2A *mm2) MM2A_MIX(mm2->hash, mm2->tail); MM2A_MIX(mm2->hash, mm2->size); - mm2->hash ^= mm2->hash >> 13; - mm2->hash *= MM2A_M; - mm2->hash ^= mm2->hash >> 15; + MM2A_MIX_FINALIZE(mm2->hash); return mm2->hash; } + +/* Non-incremental version, quicker for small keys. */ +uint32_t BLI_hash_mm2(const unsigned char *data, size_t len, uint32_t seed) +{ + /* Initialize the hash to a 'random' value */ + uint32_t h = seed ^ len; + + /* Mix 4 bytes at a time into the hash */ + for (; len >= 4; data += 4, len -= 4) { + uint32_t k = *(uint32_t *)data; + + MM2A_MIX(h, k); + } + + /* Handle the last few bytes of the input array */ + switch (len) { + case 3: + h ^= data[2] << 16; + /* fall through */ + case 2: + h ^= data[1] << 8; + /* fall through */ + case 1: + h ^= data[0]; + h *= MM2A_M; + }; + + /* Do a few final mixes of the hash to ensure the last few bytes are well-incorporated. */ + MM2A_MIX_FINALIZE(h); + + return h; +} + |