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