/*

 *  MurmurHash.c

 *  MYUtilities

 *

 *  This file created by Jens Alfke on 3/17/08.

 *  Algorithm & source code by Austin Appleby, released to public domain.

 *  <http://murmurhash.googlepages.com/>

 *  Downloaded 3/16/2008.

 *  Modified slightly by Jens Alfke (use standard uint32_t and size_t types;

 *  change 'm' and 'r' to #defines for better C compatibility.)

 *

 */

#include "MurmurHash.h"

//-----------------------------------------------------------------------------

// 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      **Jens: I fixed this by changing 'unsigned int' to 'uint32_t'**

// 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.

uint32_t MurmurHash2 ( const void * key, size_t len, uint32_t seed )

{

    // 'm' and 'r' are mixing constants generated offline.

    // They're not really 'magic', they just happen to work well.

    #define m 0x5bd1e995

    #define r 24

    // Initialize the hash to a 'random' value

    uint32_t h = seed ^ len;

    // Mix 4 bytes at a time into the hash

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

    while(len >= 4)

    {

        uint32_t k = *(uint32_t *)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;

}