src/cx/hash_key.h

Wed, 08 Feb 2023 20:26:26 +0100

author
Mike Becker <universe@uap-core.de>
date
Wed, 08 Feb 2023 20:26:26 +0100
changeset 654
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Automated merge

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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 * \file hash_key.h
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30 * \brief Interface for map implementations.
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31 * \author Mike Becker
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32 * \author Olaf Wintermann
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33 * \version 3.0
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34 * \copyright 2-Clause BSD License
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35 */
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36
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37
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38 #ifndef UCX_HASH_KEY_H
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39 #define UCX_HASH_KEY_H
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40
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41 #include "stddef.h"
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42
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43 #ifdef __cplusplus
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44 extern "C" {
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45 #endif
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46
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47 /** Internal structure for a key within a hash map. */
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48 struct cx_hash_key_s {
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49 /** The key data. */
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50 union {
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51 unsigned char *bytes;
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52 unsigned char const *cbytes;
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53 char *str;
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54 char const *cstr;
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55 void *obj;
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56 void const *cobj;
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57 } data;
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58 /**
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59 * The key data length.
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60 */
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61 size_t len;
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62 /** The hash value of the key data. */
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63 unsigned hash;
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64 };
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65
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66 /**
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67 * Type for a hash key.
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68 */
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69 typedef struct cx_hash_key_s CxHashKey;
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70
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71 /**
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72 * Computes a murmur2 32 bit hash.
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73 *
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74 * You need to initialize \c data and \c len in the key struct.
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75 * The hash is then directly written to that struct.
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76 *
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77 * \note If \c data is \c NULL, the hash is defined as 1574210520.
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78 *
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79 * @param key the key, the hash shall be computed for
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80 */
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81 void cx_hash_murmur(CxHashKey *key);
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82
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83 /**
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84 * Computes a hash key from a string.
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85 *
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86 * The string needs to be zero-terminated.
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87 *
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88 * @param str the string
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89 * @return the hash key
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90 */
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91 __attribute__((__warn_unused_result__))
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92 CxHashKey cx_hash_key_str(char const *str);
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93
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94 /**
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95 * Computes a hash key from a byte array.
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96 *
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97 * @param bytes the array
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98 * @param len the length
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99 * @return the hash key
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100 */
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101 __attribute__((__warn_unused_result__))
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102 CxHashKey cx_hash_key_bytes(
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103 unsigned char const *bytes,
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104 size_t len
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105 );
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106
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107 /**
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108 * Computes a hash key for an arbitrary object.
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109 *
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110 * The computation uses the in-memory representation that might not be
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111 * the same on different platforms. Therefore, this hash should not be
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112 * used for data exchange with different machines.
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113 *
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114 * @param obj a pointer to an arbitrary object
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115 * @param len the length of object in memory
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116 * @return the hash key
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117 */
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118 __attribute__((__warn_unused_result__))
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119 CxHashKey cx_hash_key(
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120 void const *obj,
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121 size_t len
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122 );
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123
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124 #ifdef __cplusplus
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125 } // extern "C"
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126 #endif
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127
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128 #endif // UCX_HASH_KEY_H

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