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