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 hash_map.h
30 * \brief Hash map implementation.
31 * \author Mike Becker
32 * \author Olaf Wintermann
33 * \version 3.0
34 * \copyright 2-Clause BSD License
35 */
36
37 #ifndef UCX_HASH_MAP_H
38 #define UCX_HASH_MAP_H
39
40 #include "map.h"
41
42 #ifdef __cplusplus
43 extern "C" {
44 #endif
45
46 /** Internal structure for an element of a hash map. */
47 struct cx_hash_map_element_s;
48
49 /**
50 * Internal structure for a hash map.
51 */
52 struct cx_hash_map_s {
53 /**
54 * Base structure for maps.
55 */
56 struct cx_map_s base;
57 /**
58 * The buckets of this map, each containing a linked list of elements.
59 */
60 struct cx_hash_map_element_s **buckets;
61 /**
62 * The number of buckets.
63 */
64 size_t bucket_count;
65 };
66
67
68 /**
69 * Creates a new hash map with the specified number of buckets.
70 *
71 * If \p buckets is zero, an implementation defined default will be used.
72 *
73 * If \p item_size is CX_STORE_POINTERS, the created map will be created as if
74 * cxMapStorePointers() was called immediately after creation.
75 *
76 * @note Iterators provided by this hash map implementation provide the remove operation.
77 * The index value of an iterator is incremented when the iterator advanced without removal.
78 * In other words, when the iterator is finished, \c index==size .
79 *
80 * @param allocator the allocator to use
81 * @param itemsize the size of one element
82 * @param buckets the initial number of buckets in this hash map
83 * @return a pointer to the new hash map
84 */
85 __attribute__((__nonnull__, __warn_unused_result__))
86 CxMap *cxHashMapCreate(
87 CxAllocator const *allocator,
88 size_t itemsize,
89 size_t buckets
90 );
91
92 /**
93 * Creates a new hash map with a default number of buckets.
94 *
95 * If \p item_size is CX_STORE_POINTERS, the created map will be created as if
96 * cxMapStorePointers() was called immediately after creation.
97 *
98 * @note Iterators provided by this hash map implementation provide the remove operation.
99 * The index value of an iterator is incremented when the iterator advanced without removal.
100 * In other words, when the iterator is finished, \c index==size .
101 *
102 * @param itemsize the size of one element
103 * @return a pointer to the new hash map
104 */
105 #define cxHashMapCreateSimple(itemsize) \
106 cxHashMapCreate(cxDefaultAllocator, itemsize, 0)
107
108 /**
109 * Increases the number of buckets, if necessary.
110 *
111 * The load threshold is \c 0.75*buckets. If the element count exceeds the load
112 * threshold, the map will 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 * 2.5 times the element count. 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 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 * @return zero on success, non-zero if a memory allocation error occurred
125 */
126 __attribute__((__nonnull__))
127 int cxMapRehash(CxMap *map);
128
129
130 #ifdef __cplusplus
131 } // extern "C"
132 #endif
133
134 #endif // UCX_HASH_MAP_H
135