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Fix SipHash-2-4 performance for non multiple of 8 buffers.

Browse source 
Code cribbed from Andrew Moon's Public Domain SipHash-2-4
implementation (which IMO is also cleaner).

Fixes bug 17544.
This commit is contained in:
Yawning Angel 2015-11-05 18:21:43 +00:00
parent 5a37061885
commit b71f6d6a47
2 changed files with 24 additions and 37 deletions
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4
changes/bug17544 Normal file
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@ -0,0 +1,4 @@
o Minor bugfix (SipHash-2-4 performance):
- Improve performance when hashing non-multiple of 8 sized buffers,
based on Andrew Moon's Public Domain SipHash-2-4 implementation.
Fixes bug 17544; bugfix on 0.2.5.3-alpha.

57
src/ext/csiphash.c
View file

@ -97,65 +97,48 @@
#endif
uint64_t siphash24(const void *src, unsigned long src_sz, const struct sipkey *key) {
const uint8_t *m = src;
uint64_t k0 = key->k0;
uint64_t k1 = key->k1;
uint64_t b = (uint64_t)src_sz << 56;
#ifdef UNALIGNED_OK
const uint64_t *in = (uint64_t*)src;
#else
/* On platforms where alignment matters, if 'in' is a pointer to a
* datatype that must be aligned, the compiler is allowed to
* generate code that assumes that it is aligned as such.
*/
const uint8_t *in = (uint8_t *)src;
#endif
uint64_t t;
uint8_t *pt, *m;
uint64_t last7 = (uint64_t)(src_sz & 0xff) << 56;
size_t i, blocks;
uint64_t v0 = k0 ^ 0x736f6d6570736575ULL;
uint64_t v1 = k1 ^ 0x646f72616e646f6dULL;
uint64_t v2 = k0 ^ 0x6c7967656e657261ULL;
uint64_t v3 = k1 ^ 0x7465646279746573ULL;
while (src_sz >= 8) {
for (i = 0, blocks = (src_sz & ~7); i < blocks; i+= 8) {
#ifdef UNALIGNED_OK
uint64_t mi = _le64toh(*in);
in += 1;
uint64_t mi = _le64toh(*(m + i));
#else
uint64_t mi;
memcpy(&mi, in, 8);
memcpy(&mi, m + i, 8);
mi = _le64toh(mi);
in += 8;
#endif
src_sz -= 8;
v3 ^= mi;
DOUBLE_ROUND(v0,v1,v2,v3);
v0 ^= mi;
}
t = 0; pt = (uint8_t*)&t; m = (uint8_t*)in;
switch (src_sz) {
case 7: pt[6] = m[6];
case 6: pt[5] = m[5];
case 5: pt[4] = m[4];
#ifdef UNALIGNED_OK
case 4: *((uint32_t*)&pt[0]) = *((uint32_t*)&m[0]); break;
#else
case 4: pt[3] = m[3];
#endif
case 3: pt[2] = m[2];
case 2: pt[1] = m[1];
case 1: pt[0] = m[0];
switch (src_sz - blocks) {
case 7: last7 |= (uint64_t)m[i + 6] << 48;
case 6: last7 |= (uint64_t)m[i + 5] << 40;
case 5: last7 |= (uint64_t)m[i + 4] << 32;
case 4: last7 |= (uint64_t)m[i + 3] << 24;
case 3: last7 |= (uint64_t)m[i + 2] << 16;
case 2: last7 |= (uint64_t)m[i + 1] << 8;
case 1: last7 |= (uint64_t)m[i + 0] ;
case 0:
default:;
}
b |= _le64toh(t);
v3 ^= b;
v3 ^= last7;
DOUBLE_ROUND(v0,v1,v2,v3);
v0 ^= b; v2 ^= 0xff;
v0 ^= last7;
v2 ^= 0xff;
DOUBLE_ROUND(v0,v1,v2,v3);
DOUBLE_ROUND(v0,v1,v2,v3);
return (v0 ^ v1) ^ (v2 ^ v3);
return v0 ^ v1 ^ v2 ^ v3;
}