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/**
* @file
* @brief Hashes.
**/
#include "AppHdr.h"
#include "hash.h"
#include "endianness.h"
//-----------------------------------------------------------------------------
// MurmurHash2, by Austin Appleby
uint32_t hash32(const void *data, int len)
{
// 'm' and 'r' are mixing constants generated offline.
// They're not really 'magic', they just happen to work well.
const uint32_t m = 0x5bd1e995;
// Initialize the hash to a 'random' value
uint32_t h = len;
const uint8_t *d = (const uint8_t*)data;
// Mix 4 bytes at a time into the hash
while (len >= 4)
{
uint32_t k = htole32(*(uint32_t *)d);
k *= m;
k ^= k >> 24;
k *= m;
h *= m;
h ^= k;
d += 4;
len -= 4;
}
// Handle the last few bytes of the input array
switch (len)
{
case 3: h ^= (uint32_t)d[2] << 16;
case 2: h ^= (uint32_t)d[1] << 8;
case 1: h ^= (uint32_t)d[0];
h *= m;
};
// Do a few final mixes of the hash to ensure the last few
// bytes are well-incorporated.
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
unsigned int hash_rand(int x, uint32_t seed, uint32_t id)
{
if (x < 2)
return 0;
uint32_t data[2] = {seed, id};
return hash32(data, 2 * sizeof(int32_t)) % x;
}
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