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/*-
* Copyright (c) 2014 Dag-Erling Smørgrav
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <sys/hash.h>
#include <sys/endian.h>
#include <sys/stdint.h>
#include <sys/types.h>
#define rol32(i32, n) ((i32) << (n) | (i32) >> (32 - (n)))
/*
* Simple implementation of the Murmur3-32 hash function.
*
* This implementation is slow but safe. It can be made significantly
* faster if the caller guarantees that the input is correctly aligned for
* 32-bit reads, and slightly faster yet if the caller guarantees that the
* length of the input is always a multiple of 4 bytes.
*/
uint32_t
murmur3_32_hash(const void *data, size_t len, uint32_t seed)
{
const uint8_t *bytes;
uint32_t hash, k;
size_t res;
/* initialization */
bytes = data;
res = len;
hash = seed;
/* main loop */
while (res >= 4) {
/* replace with le32toh() if input is aligned */
k = le32dec(bytes);
bytes += 4;
res -= 4;
k *= 0xcc9e2d51;
k = rol32(k, 15);
k *= 0x1b873593;
hash ^= k;
hash = rol32(hash, 13);
hash *= 5;
hash += 0xe6546b64;
}
/* remainder */
/* remove if input length is a multiple of 4 */
if (res > 0) {
k = 0;
switch (res) {
case 3:
k |= bytes[2] << 16;
case 2:
k |= bytes[1] << 8;
case 1:
k |= bytes[0];
k *= 0xcc9e2d51;
k = rol32(k, 15);
k *= 0x1b873593;
hash ^= k;
break;
}
}
/* finalize */
hash ^= (uint32_t)len;
hash ^= hash >> 16;
hash *= 0x85ebca6b;
hash ^= hash >> 13;
hash *= 0xc2b2ae35;
hash ^= hash >> 16;
return (hash);
}
/*
* Simplified version of the above optimized for aligned sequences of
* 32-bit words. The count argument is the number of words, not the
* length in bytes.
*/
uint32_t
murmur3_32_hash32(const uint32_t *data, size_t count, uint32_t seed)
{
uint32_t hash, k;
size_t res;
/* iterate */
for (res = count, hash = seed; res > 0; res--, data++) {
k = le32toh(*data);
k *= 0xcc9e2d51;
k = rol32(k, 15);
k *= 0x1b873593;
hash ^= k;
hash = rol32(hash, 13);
hash *= 5;
hash += 0xe6546b64;
}
/* finalize */
hash ^= (uint32_t)count;
hash ^= hash >> 16;
hash *= 0x85ebca6b;
hash ^= hash >> 13;
hash *= 0xc2b2ae35;
hash ^= hash >> 16;
return (hash);
}
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