Something like GLib but tiny
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// Code taken from https://github.com/floodyberry/siphash with some edits.
//
// To the extent possible under law, the author(s) have dedicated all copyright
// and related and neighboring rights to this software to the public domain
// worldwide. This software is distributed without any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication along
// with this software. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
inline static uint64_t
u8to64_le (const unsigned char *p)
{
return
(uint64_t) p[0] |
(uint64_t) p[1] << 8 |
(uint64_t) p[2] << 16 |
(uint64_t) p[3] << 24 |
(uint64_t) p[4] << 32 |
(uint64_t) p[5] << 40 |
(uint64_t) p[6] << 48 |
(uint64_t) p[7] << 56 ;
}
static uint64_t
siphash (const unsigned char key[16], const unsigned char *m, size_t len)
{
uint64_t v0, v1, v2, v3;
uint64_t mi, k0, k1;
uint64_t last7;
size_t i, blocks;
k0 = u8to64_le (key + 0);
k1 = u8to64_le (key + 8);
v0 = k0 ^ 0x736f6d6570736575ull;
v1 = k1 ^ 0x646f72616e646f6dull;
v2 = k0 ^ 0x6c7967656e657261ull;
v3 = k1 ^ 0x7465646279746573ull;
last7 = (uint64_t) (len & 0xff) << 56;
#define ROTL64(a,b) (((a)<<(b))|((a)>>(64-b)))
#define COMPRESS \
v0 += v1; v2 += v3; \
v1 = ROTL64 (v1,13); v3 = ROTL64 (v3,16); \
v1 ^= v0; v3 ^= v2; \
v0 = ROTL64 (v0,32); \
v2 += v1; v0 += v3; \
v1 = ROTL64 (v1,17); v3 = ROTL64 (v3,21); \
v1 ^= v2; v3 ^= v0; \
v2 = ROTL64(v2,32);
for (i = 0, blocks = (len & ~(size_t) 7); i < blocks; i += 8)
{
mi = u8to64_le (m + i);
v3 ^= mi;
COMPRESS
COMPRESS
v0 ^= mi;
}
switch (len - blocks)
{
case 7: last7 |= (uint64_t) m[i + 6] << 48; // Fall-through
case 6: last7 |= (uint64_t) m[i + 5] << 40; // Fall-through
case 5: last7 |= (uint64_t) m[i + 4] << 32; // Fall-through
case 4: last7 |= (uint64_t) m[i + 3] << 24; // Fall-through
case 3: last7 |= (uint64_t) m[i + 2] << 16; // Fall-through
case 2: last7 |= (uint64_t) m[i + 1] << 8; // Fall-through
case 1: last7 |= (uint64_t) m[i + 0] ; // Fall-through
default:;
};
v3 ^= last7;
COMPRESS
COMPRESS
v0 ^= last7;
v2 ^= 0xff;
COMPRESS
COMPRESS
COMPRESS
COMPRESS
return v0 ^ v1 ^ v2 ^ v3;
}