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| author | Grigori Goronzy <greg@chown.ath.cx> | 2014-01-29 05:25:40 +0100 |
|---|---|---|
| committer | Grigori Goronzy <greg@chown.ath.cx> | 2014-01-29 05:27:29 +0100 |
| commit | f466b9678b4b68e56d7374dea51218348d628b06 (patch) | |
| tree | 3e130afc1a9ff88d32fb826549afdb4b0a9e1344 | |
| parent | 8adee493913fbf21c285f15717270757e87b4779 (diff) | |
| download | libass-f466b9678b4b68e56d7374dea51218348d628b06.tar.bz2 libass-f466b9678b4b68e56d7374dea51218348d628b06.tar.xz | |
Unroll FNV-1A hash function
Unroll the hash function with Duff's device for improved performance.
| -rw-r--r-- | libass/ass_utils.h | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/libass/ass_utils.h b/libass/ass_utils.h index 6d795f0..4e2ba6c 100644 --- a/libass/ass_utils.h +++ b/libass/ass_utils.h @@ -132,11 +132,16 @@ static inline int rot_key(double a) static inline unsigned fnv_32a_buf(void *buf, size_t len, unsigned hval) { unsigned char *bp = buf; - unsigned char *be = bp + len; - while (bp < be) { - hval ^= (unsigned) *bp++; - hval *= FNV1_32A_PRIME; + size_t n = (len + 3) / 4; + + switch (len % 4) { + case 0: do { hval ^= (unsigned) *bp++; hval *= FNV1_32A_PRIME; + case 3: hval ^= (unsigned) *bp++; hval *= FNV1_32A_PRIME; + case 2: hval ^= (unsigned) *bp++; hval *= FNV1_32A_PRIME; + case 1: hval ^= (unsigned) *bp++; hval *= FNV1_32A_PRIME; + } while (--n > 0); } + return hval; } static inline unsigned fnv_32a_str(char *str, unsigned hval) |