Thu, 19 May 2022 14:30:20 +0200
#189 basic map implementation
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 * \file map.h
30 * \brief Interface for map implementations.
31 * \author Mike Becker
32 * \author Olaf Wintermann
33 * \version 3.0
34 * \copyright 2-Clause BSD License
35 */
37 #ifndef UCX_HASH_MAP_H
38 #define UCX_HASH_MAP_H
40 #include "map.h"
42 #ifdef __cplusplus
43 extern "C" {
44 #endif
46 /** Internal structure for a key within a hash map. */
47 struct cx_hash_map_key_s {
48 /** The key data. */
49 unsigned char *data;
50 /**
51 * The key data length.
52 */
53 size_t len;
54 /** The hash value of the key data. */
55 unsigned hash;
56 };
58 /** Internal structure for an element of a hash map. */
59 struct cx_hash_map_element_s {
60 /** The value data. */
61 void *data;
63 /** A pointer to the next element in the current bucket. */
64 struct cx_hash_map_element_s *next;
66 /** The corresponding key. */
67 struct cx_hash_map_key_s key;
68 };
70 /**
71 * Internal structure for a hash map.
72 */
73 struct cx_hash_map_s {
74 /**
75 * Base structure for maps.
76 */
77 struct cx_map_s base;
78 /**
79 * The buckets of this map, each containing a linked list of elements.
80 */
81 struct cx_hash_map_element_s **buckets;
82 /**
83 * The number of buckets.
84 */
85 size_t bucket_count;
86 };
89 /**
90 * Creates a new hash map with the specified number of buckets.
91 *
92 * If \p buckets is zero, an implementation defined default will be used.
93 *
94 * @note Iterators provided by this hash map implementation do provide the remove operation, because
95 * a remove never causes an immediate rehashing. The iterators are also position-aware in the sense
96 * that the index is initialized with zero and incremented when the iterator advances.
97 *
98 * @param allocator the allocator to use
99 * @param buckets the initial number of buckets in this hash map
100 * @return a pointer to the new hash map
101 */
102 __attribute__((__nonnull__, __warn_unused_result__))
103 CxMap *cxHashMapCreate(
104 CxAllocator *allocator,
105 size_t buckets
106 );
108 /**
109 * Increases the number of buckets, if necessary.
110 *
111 * The load value is \c loadFactor*buckets. If the element count exceeds the load
112 * value, the map needs to be rehashed. Otherwise, no action is performed and
113 * this function simply returns 0.
114 *
115 * The rehashing process ensures, that the number of buckets is at least
116 * \p bucketFactor times the number of stored items. So there is enough room for additional
117 * elements without the need of another soon rehashing.
118 *
119 * You can use this function after filling a map to dramatically increase access performance.
120 *
121 * @note If the specified map is not a hash map, the behavior is undefined.
122 *
123 * @param map the map to rehash
124 * @param loadFactor a percentage threshold for the load of the map
125 * @param bucketFactor a factor for the number of buckets that shall be available after rehashing
126 * @return zero on success, non-zero if a memory allocation error occurred
127 */
128 __attribute__((__nonnull__))
129 int cxMapRehash2(
130 CxMap *map,
131 float loadFactor,
132 float bucketFactor
133 );
135 /**
136 * Rehashes the map with load factor 0.75 and bucket factor 2.5.
137 *
138 * @param map the map to rehash
139 * @return zero on success, non-zero if a memory allocation error occurred
140 * @see cxMapRehash2()
141 */
142 __attribute__((__nonnull__))
143 static inline int cxMapRehash(CxMap *map) {
144 return cxMapRehash2(map, 0.75f, 2.5f);
145 }
148 #ifdef __cplusplus
149 } // extern "C"
150 #endif
152 #endif // UCX_HASH_MAP_H