comparison: src/hash_map.c
src/hash_map.c
- changeset 549
- d7f0b5a9a985
- child 550
- 89b2a83728b1
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| 548:459bca1cdf8d | 549:d7f0b5a9a985 |
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| 1 /* | |
| 2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER. | |
| 3 * | |
| 4 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved. | |
| 5 * | |
| 6 * Redistribution and use in source and binary forms, with or without | |
| 7 * modification, are permitted provided that the following conditions are met: | |
| 8 * | |
| 9 * 1. Redistributions of source code must retain the above copyright | |
| 10 * notice, this list of conditions and the following disclaimer. | |
| 11 * | |
| 12 * 2. Redistributions in binary form must reproduce the above copyright | |
| 13 * notice, this list of conditions and the following disclaimer in the | |
| 14 * documentation and/or other materials provided with the distribution. | |
| 15 * | |
| 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | |
| 17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE | |
| 20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
| 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF | |
| 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS | |
| 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN | |
| 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
| 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
| 26 * POSSIBILITY OF SUCH DAMAGE. | |
| 27 */ | |
| 28 | |
| 29 #include <string.h> | |
| 30 #include "cx/hash_map.h" | |
| 31 | |
| 32 /** | |
| 33 * Computes a murmur hash-2. | |
| 34 * | |
| 35 * @param data the data to hash | |
| 36 * @param len the length of the data | |
| 37 * @return the murmur hash-2 of the data | |
| 38 */ | |
| 39 static unsigned cx_hash_map_murmur( | |
| 40 unsigned char const *data, | |
| 41 size_t len | |
| 42 ) { | |
| 43 unsigned m = 0x5bd1e995; | |
| 44 unsigned r = 24; | |
| 45 unsigned h = 25 ^ len; | |
| 46 unsigned i = 0; | |
| 47 while (len >= 4) { | |
| 48 unsigned k = data[i + 0] & 0xFF; | |
| 49 k |= (data[i + 1] & 0xFF) << 8; | |
| 50 k |= (data[i + 2] & 0xFF) << 16; | |
| 51 k |= (data[i + 3] & 0xFF) << 24; | |
| 52 | |
| 53 k *= m; | |
| 54 k ^= k >> r; | |
| 55 k *= m; | |
| 56 | |
| 57 h *= m; | |
| 58 h ^= k; | |
| 59 | |
| 60 i += 4; | |
| 61 len -= 4; | |
| 62 } | |
| 63 | |
| 64 switch (len) { | |
| 65 case 3: | |
| 66 h ^= (data[i + 2] & 0xFF) << 16; | |
| 67 __attribute__((__fallthrough__)); | |
| 68 case 2: | |
| 69 h ^= (data[i + 1] & 0xFF) << 8; | |
| 70 __attribute__((__fallthrough__)); | |
| 71 case 1: | |
| 72 h ^= (data[i + 0] & 0xFF); | |
| 73 h *= m; | |
| 74 __attribute__((__fallthrough__)); | |
| 75 default: | |
| 76 /* do nothing */; | |
| 77 } | |
| 78 | |
| 79 h ^= h >> 13; | |
| 80 h *= m; | |
| 81 h ^= h >> 15; | |
| 82 | |
| 83 return h; | |
| 84 } | |
| 85 | |
| 86 | |
| 87 /** | |
| 88 * Creates a hash map key based on the given data. | |
| 89 * | |
| 90 * This function implicitly computes the hash. | |
| 91 * | |
| 92 * @attention The data will be copied to the key structure. | |
| 93 * | |
| 94 * @param data the data for the key | |
| 95 * @return the computed key | |
| 96 */ | |
| 97 static struct cx_hash_map_key_s cx_hash_map_key(CxDataPtr data) { | |
| 98 unsigned char *target = malloc(data.len); | |
| 99 memcpy(target, data.data, data.len); | |
| 100 struct cx_hash_map_key_s key; | |
| 101 key.data.data = target; | |
| 102 key.data.len = data.len; | |
| 103 key.hash = cx_hash_map_murmur(target, data.len); | |
| 104 return key; | |
| 105 } |
