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/**
* Seccomp Library hash code
*
*/
/*
* This code is based on MurmurHash3.cpp from Austin Appleby and is placed in
* the public domain.
*
* https://github.com/aappleby/smhasher
*
*/
#include <stdlib.h>
#include <inttypes.h>
#include "hash.h"
static inline uint32_t getblock32(const uint32_t *p, int i)
{
return p[i];
}
static inline uint32_t rotl32(uint32_t x, int8_t r)
{
return (x << r) | (x >> (32 - r));
}
static inline uint32_t fmix32(uint32_t h)
{
h ^= h >> 16;
h *= 0x85ebca6b;
h ^= h >> 13;
h *= 0xc2b2ae35;
h ^= h >> 16;
return h;
}
/* NOTE: this is an implementation of MurmurHash3_x86_32 */
uint32_t hash(const void *key, size_t length)
{
const uint8_t *data = (const uint8_t *)key;
const uint32_t *blocks;
const uint8_t *tail;
const int nblocks = length / 4;
const uint32_t c1 = 0xcc9e2d51;
const uint32_t c2 = 0x1b873593;
uint32_t k1;
uint32_t k2 = 0;
int i;
/* NOTE: we always force a seed of 0 */
uint32_t h1 = 0;
/* body */
blocks = (const uint32_t *)(data + nblocks * 4);
for(i = -nblocks; i; i++) {
k1 = getblock32(blocks, i);
k1 *= c1;
k1 = rotl32(k1, 15);
k1 *= c2;
h1 ^= k1;
h1 = rotl32(h1, 13);
h1 = h1 * 5 + 0xe6546b64;
}
/* tail */
tail = (const uint8_t *)(data + nblocks * 4);
switch(length & 3) {
case 3:
k2 ^= tail[2] << 16;
case 2:
k2 ^= tail[1] << 8;
case 1:
k2 ^= tail[0];
k2 *= c1;
k2 = rotl32(k2, 15);
k2 *= c2;
h1 ^= k2;
};
/* finalization */
h1 ^= length;
h1 = fmix32(h1);
return h1;
}
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