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 will be created as if
73 * cxMapStorePointers() was called immediately after creation.
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 removal.
77 * In other words, when the iterator is finished, @c index==size .
78 *
79 * @param allocator the allocator to use
80 * (if @c NULL, a default stdlib allocator will be used)
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 cx_attr_nodiscard
86 cx_attr_malloc
87 cx_attr_dealloc(cxMapFree, 1)
88 CxMap *cxHashMapCreate(
89 const CxAllocator *allocator,
90 size_t itemsize,
91 size_t buckets
92 );
93
94 /**
95 * Creates a new hash map with a default number of buckets.
96 *
97 * If @p elem_size is CX_STORE_POINTERS, the created map will be created as if
98 * cxMapStorePointers() was called immediately after creation.
99 *
100 * @note Iterators provided by this hash map implementation provide the remove operation.
101 * The index value of an iterator is incremented when the iterator advanced without removal.
102 * In other words, when the iterator is finished, @c index==size .
103 *
104 * @param itemsize (@c size_t) the size of one element
105 * @return (@c CxMap*) a pointer to the new hash map
106 */
107 #define cxHashMapCreateSimple(itemsize) cxHashMapCreate(NULL, itemsize, 0)
108
109 /**
110 * Increases the number of buckets, if necessary.
111 *
112 * The load threshold is @c 0.75*buckets. If the element count exceeds the load
113 * threshold, the map will be rehashed. Otherwise, no action is performed and
114 * this function simply returns 0.
115 *
116 * The rehashing process ensures, that the number of buckets is at least
117 * 2.5 times the element count. So there is enough room for additional
118 * elements without the need of another soon rehashing.
119 *
120 * You can use this function after filling a map to increase access performance.
121 *
122 * @note If the specified map is not a hash map, the behavior is undefined.
123 *
124 * @param map the map to rehash
125 * @retval zero success
126 * @retval non-zero if a memory allocation error occurred
127 */
128 cx_attr_nonnull
129 int cxMapRehash(CxMap *map);
130
131
132 #ifdef __cplusplus
133 } // extern "C"
134 #endif
135
136 #endif // UCX_HASH_MAP_H
137