src/hash_key.c

Thu, 23 Feb 2023 22:24:26 +0100

author
Mike Becker <universe@uap-core.de>
date
Thu, 23 Feb 2023 22:24:26 +0100
changeset 660
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parent 628
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child 678
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permissions
-rw-r--r--

add some asserts

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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 "cx/hash_key.h"
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30 #include <string.h>
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31
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32 void cx_hash_murmur(CxHashKey *key) {
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33 unsigned char const *data = key->data.cbytes;
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34 if (data == NULL) {
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35 // extension: special value for NULL
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36 key->hash = 1574210520u;
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37 return;
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38 }
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39 size_t len = key->len;
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40
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41 unsigned m = 0x5bd1e995;
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42 unsigned r = 24;
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43 unsigned h = 25 ^ len;
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44 unsigned i = 0;
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45 while (len >= 4) {
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46 unsigned k = data[i + 0] & 0xFF;
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47 k |= (data[i + 1] & 0xFF) << 8;
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48 k |= (data[i + 2] & 0xFF) << 16;
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49 k |= (data[i + 3] & 0xFF) << 24;
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50
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51 k *= m;
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52 k ^= k >> r;
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53 k *= m;
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54
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55 h *= m;
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56 h ^= k;
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57
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58 i += 4;
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59 len -= 4;
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60 }
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61
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62 switch (len) {
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63 case 3:
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64 h ^= (data[i + 2] & 0xFF) << 16;
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65 __attribute__((__fallthrough__));
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66 case 2:
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67 h ^= (data[i + 1] & 0xFF) << 8;
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68 __attribute__((__fallthrough__));
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69 case 1:
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70 h ^= (data[i + 0] & 0xFF);
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71 h *= m;
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72 __attribute__((__fallthrough__));
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73 default: // do nothing
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74 ;
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75 }
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76
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77 h ^= h >> 13;
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78 h *= m;
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79 h ^= h >> 15;
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80
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81 key->hash = h;
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82 }
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83
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84 CxHashKey cx_hash_key_str(char const *str) {
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85 CxHashKey key;
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86 key.data.cstr = str;
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87 key.len = str == NULL ? 0 : strlen(str);
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88 cx_hash_murmur(&key);
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89 return key;
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90 }
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91
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92 CxHashKey cx_hash_key_bytes(
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93 unsigned char const *bytes,
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94 size_t len
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95 ) {
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96 CxHashKey key;
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97 key.data.cbytes = bytes;
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98 key.len = len;
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99 cx_hash_murmur(&key);
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100 return key;
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101 }
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102
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103 CxHashKey cx_hash_key(
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104 void const *obj,
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105 size_t len
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106 ) {
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107 CxHashKey key;
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108 key.data.cobj = obj;
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109 key.len = len;
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110 cx_hash_murmur(&key);
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111 return key;
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112 }

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