92 lines
2.4 KiB
C
92 lines
2.4 KiB
C
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/*
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* The MIT License (MIT)
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*
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* Copyright (c) 2014 Joseph Werle
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <stdint.h>
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#include "murmurhash.h"
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uint32_t
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murmurhash (const char *key, uint32_t len, uint32_t seed) {
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uint32_t c1 = 0xcc9e2d51;
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uint32_t c2 = 0x1b873593;
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uint32_t r1 = 15;
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uint32_t r2 = 13;
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uint32_t m = 5;
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uint32_t n = 0xe6546b64;
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uint32_t h = 0;
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uint32_t k = 0;
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uint8_t *d = (uint8_t *) key; // 32 bit extract from `key'
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const uint32_t *chunks = NULL;
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const uint8_t *tail = NULL; // tail - last 8 bytes
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int i = 0;
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int l = len / 4; // chunk length
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h = seed;
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chunks = (const uint32_t *) (d + l * 4); // body
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tail = (const uint8_t *) (d + l * 4); // last 8 byte chunk of `key'
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// for each 4 byte chunk of `key'
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for (i = -l; i != 0; ++i) {
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// next 4 byte chunk of `key'
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k = chunks[i];
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// encode next 4 byte chunk of `key'
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k *= c1;
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k = (k << r1) | (k >> (32 - r1));
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k *= c2;
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// append to hash
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h ^= k;
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h = (h << r2) | (h >> (32 - r2));
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h = h * m + n;
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}
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k = 0;
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// remainder
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switch (len & 3) { // `len % 4'
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case 3: k ^= (tail[2] << 16);
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case 2: k ^= (tail[1] << 8);
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case 1:
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k ^= tail[0];
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k *= c1;
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k = (k << r1) | (k >> (32 - r1));
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k *= c2;
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h ^= k;
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}
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h ^= len;
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h ^= (h >> 16);
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h *= 0x85ebca6b;
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h ^= (h >> 13);
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h *= 0xc2b2ae35;
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h ^= (h >> 16);
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return h;
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}
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