MurmurHashNeutral2.h

/*-----------------------------------------------------------------------------
 * MurmurHashNeutral2, by Austin Appleby
 *
 * Same as MurmurHash2, but endian- and alignment-neutral.
 * Half the speed though, alas.
 */
 /* Code released into the public domain. */
 /* C-ification and adaption to perl.h by Steffen Mueller 2009-11-03 */

#include "perl.h"

#ifndef _MurmurHashNeutral2_h_
#define _MurmurHashNeutral2_h_

U32 CXSA_MurmurHashNeutral2(const void* key, STRLEN len, U32 _seed) {
    const unsigned int m = 0x5bd1e995;
    const int r = 24;

    unsigned int h = _seed ^ len;

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

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

        k  = data[0];
        k |= data[1] << 8;
        k |= data[2] << 16;
        k |= data[3] << 24;

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

        h *= m;
        h ^= k;

        data += 4;
        len -= 4;
    }

    switch(len)  {
        case 3:
            h ^= data[2] << 16;
            /* fall through */
        case 2:
            h ^= data[1] << 8;
            /* fall through */
        case 1:
            h ^= data[0];
            h *= m;
    };

    h ^= h >> 13;
    h *= m;
    h ^= h >> 15;

    return (U32)h;
}

#endif