src/cx/hash_map.h

Fri, 12 Aug 2022 16:48:59 +0200

author
Mike Becker <universe@uap-core.de>
date
Fri, 12 Aug 2022 16:48:59 +0200
changeset 574
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parent 563
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child 658
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permissions
-rw-r--r--

invert if-condition in preparation for the next bugfix

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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_map.h
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30 * \brief Hash map implementation.
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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 #ifndef UCX_HASH_MAP_H
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38 #define UCX_HASH_MAP_H
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39
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40 #include "map.h"
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41
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42 #ifdef __cplusplus
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43 extern "C" {
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44 #endif
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45
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46 /** Internal structure for an element of a hash map. */
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47 struct cx_hash_map_element_s {
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48 /** The value data. */
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49 void *data;
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50
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51 /** A pointer to the next element in the current bucket. */
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52 struct cx_hash_map_element_s *next;
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53
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54 /** The corresponding key. */
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55 CxHashKey key;
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56 };
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57
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58 /**
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59 * Internal structure for a hash map.
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60 */
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61 struct cx_hash_map_s {
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62 /**
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63 * Base structure for maps.
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64 */
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65 struct cx_map_s base;
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66 /**
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67 * The buckets of this map, each containing a linked list of elements.
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68 */
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69 struct cx_hash_map_element_s **buckets;
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70 /**
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71 * The number of buckets.
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72 */
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73 size_t bucket_count;
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74 };
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75
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76
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77 /**
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78 * Creates a new hash map with the specified number of buckets.
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79 *
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80 * If \p buckets is zero, an implementation defined default will be used.
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81 *
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82 * @note Iterators provided by this hash map implementation provide the remove operation.
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83 * The index value of an iterator is the incremented when the iterator advanced without removal.
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84 * In other words, when the iterator is finished, \c index==size .
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85 *
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86 * @param allocator the allocator to use
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87 * @param buckets the initial number of buckets in this hash map
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88 * @return a pointer to the new hash map
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89 */
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90 __attribute__((__nonnull__, __warn_unused_result__))
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91 CxMap *cxHashMapCreate(
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92 CxAllocator *allocator,
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93 size_t buckets
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94 );
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95
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96 /**
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97 * Increases the number of buckets, if necessary.
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98 *
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99 * The load threshold is \c 0.75*buckets. If the element count exceeds the load
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100 * threshold, the map will be rehashed. Otherwise, no action is performed and
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101 * this function simply returns 0.
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102 *
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103 * The rehashing process ensures, that the number of buckets is at least
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104 * 2.5 times the element count. So there is enough room for additional
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105 * elements without the need of another soon rehashing.
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106 *
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107 * You can use this function after filling a map to increase access performance.
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108 *
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109 * @note If the specified map is not a hash map, the behavior is undefined.
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110 *
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111 * @param map the map to rehash
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112 * @return zero on success, non-zero if a memory allocation error occurred
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113 */
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114 __attribute__((__nonnull__))
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115 int cxMapRehash(CxMap *map);
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116
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117
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118 #ifdef __cplusplus
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119 } // extern "C"
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120 #endif
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121
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122 #endif // UCX_HASH_MAP_H

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