

#ifndef MURMURHASH2_C
#define MURMURHASH2_C

#define     MURMURHASH2_DIGEST_LENGTH   4

/*
 * -----------------------------------------------------------------------------
 * MurmurHash2, by Austin Appleby

 * Note - This code makes a few assumptions about how your machine behaves -

 * 1. We can read a 4-byte value from any address without crashing
 * 2. sizeof(int) == 4

 * And it has a few limitations -

 * 1. It will not work incrementally.
 * 2. It will not produce the same results on little-endian and big-endian
 *    machines.
 */

unsigned int MurmurHash2 ( const void * key, int len, unsigned int seed )
{
	/*
         * 'm' and 'r' are mixing constants generated offline.
	 * They're not really 'magic', they just happen to work well.
         */

	const unsigned int m = 0x5bd1e995;
	const int r = 24;

	/* Initialize the hash to a 'random' value */

	unsigned int h = seed ^ len;

	/* Mix 4 bytes at a time into the hash */

	const unsigned char * data = (const unsigned char *)key;

	while(len >= 4)
	{
		unsigned int k = *(unsigned int *)data;

		k *= m;
		k ^= k >> r;
		k *= m;

		h *= m;
		h ^= k;

		data += 4;
		len -= 4;
	}

	/* Handle the last few bytes of the input array */

	switch(len)
	{
	case 3: h ^= data[2] << 16;
	case 2: h ^= data[1] << 8;
	case 1: h ^= data[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;
}

#endif
