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 * @copyright 2-Clause BSD License
34 */
35
36 #ifndef UCX_HASH_MAP_H
37 #define UCX_HASH_MAP_H
38
39 #include "map.h"
40
41 #ifdef __cplusplus
42 extern "C" {
43 #endif
44
45 /** Internal structure for an element of a hash map. */
46 struct cx_hash_map_element_s;
47
48 /**
49 * Internal structure for a hash map.
50 */
51 struct cx_hash_map_s {
52 /**
53 * Base structure for maps.
54 */
55 struct cx_map_s base;
56 /**
57 * The buckets of this map, each containing a linked list of elements.
58 */
59 struct cx_hash_map_element_s **buckets;
60 /**
61 * The number of buckets.
62 */
63 size_t bucket_count;
64 };
65
66
67 /**
68 * Creates a new hash map with the specified number of buckets.
69 *
70 * If @p buckets is zero, an implementation defined default will be used.
71 *
72 * If @p elem_size is #CX_STORE_POINTERS, the created map stores pointers instead of
73 * copies of the added elements.
74 *
75 * @note Iterators provided by this hash map implementation provide the remove operation.
76 * The index value of an iterator is incremented when the iterator advanced without
77 * removing an entry.
78 * In other words, when the iterator is finished, @c index==size .
79 *
80 * @param allocator the allocator to use
81 * (if @c NULL, the cxDefaultAllocator will be used)
82 * @param itemsize the size of one element
83 * @param buckets the initial number of buckets in this hash map
84 * @return a pointer to the new hash map
85 */
86 cx_attr_nodiscard cx_attr_malloc cx_attr_dealloc(cxMapFree, 1)
87 CX_EXPORT CxMap *cxHashMapCreate(const CxAllocator *allocator,
88 size_t itemsize, size_t buckets);
89
90 /**
91 * Creates a new hash map with a default number of buckets.
92 *
93 * If @p elem_size is #CX_STORE_POINTERS, the created map stores pointers instead of
94 * copies of the added elements.
95 *
96 * @note Iterators provided by this hash map implementation provide the remove operation.
97 * The index value of an iterator is incremented when the iterator advanced without
98 * removing an entry.
99 * In other words, when the iterator is finished, @c index==size .
100 *
101 * @param itemsize (@c size_t) the size of one element
102 * @return (@c CxMap*) a pointer to the new hash map
103 */
104 #define cxHashMapCreateSimple(itemsize) cxHashMapCreate(NULL, itemsize, 0)
105
106 /**
107 * Increases the number of buckets, if necessary.
108 *
109 * The load threshold is @c 0.75*buckets. If the element count exceeds the load
110 * threshold, the map will be rehashed. Otherwise, no action is performed, and
111 * this function simply returns 0.
112 *
113 * The rehashing process ensures that the number of buckets is at least
114 * 2.5 times the element count. So there is enough room for additional
115 * elements without the need of another soon rehashing.
116 *
117 * You can use this function after filling a map to increase access performance.
118 *
119 * @note If the specified map is not a hash map, the behavior is undefined.
120 *
121 * @param map the map to rehash
122 * @retval zero success
123 * @retval non-zero if a memory allocation error occurred
124 */
125 cx_attr_nonnull
126 CX_EXPORT int cxMapRehash(CxMap *map);
127
128
129 #ifdef __cplusplus
130 } // extern "C"
131 #endif
132
133 #endif // UCX_HASH_MAP_H
134