ucx: src/cx/hash_map.h@56c62780582e

     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

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    23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

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    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  */

    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 an element of a hash map. */

    47 struct cx_hash_map_element_s;

    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 };

    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  * @note Iterators provided by this hash map implementation provide the remove operation.

    74  * The index value of an iterator is the incremented when the iterator advanced without removal.

    75  * In other words, when the iterator is finished, \c index==size .

    76  *

    77  * @param allocator the allocator to use

    78  * @param itemsize the size of one element

    79  * @param buckets the initial number of buckets in this hash map

    80  * @return a pointer to the new hash map

    81  */

    82 __attribute__((__nonnull__, __warn_unused_result__))

    83 CxMap *cxHashMapCreate(

    84         CxAllocator *allocator,

    85         size_t itemsize,

    86         size_t buckets

    87 );

    89 /**

    90  * Convenience function for creating a hash map that is storing pointers.

    91  *

    92  * If \p buckets is zero, an implementation defined default will be used.

    93  *

    94  * @param allocator the allocator to use

    95  * @param buckets the initial number of buckets in this hash map

    96  * @return a pointer to the new hash map

    97  */

    98 __attribute__((__nonnull__, __warn_unused_result__))

    99 static inline CxMap *cxHashMapCreateForPointers(

   100         CxAllocator *allocator,

   101         size_t buckets

   102 ) {

   103     CxMap *map = cxHashMapCreate(allocator, sizeof(void *), buckets);

   104     if (map != NULL) {

   105         map->store_pointers = true;

   106     }

   107     return map;

   108 }

   110 /**

   111  * Increases the number of buckets, if necessary.

   112  *

   113  * The load threshold is \c 0.75*buckets. If the element count exceeds the load

   114  * threshold, the map will be rehashed. Otherwise, no action is performed and

   115  * this function simply returns 0.

   116  *

   117  * The rehashing process ensures, that the number of buckets is at least

   118  * 2.5 times the element count. So there is enough room for additional

   119  * elements without the need of another soon rehashing.

   120  *

   121  * You can use this function after filling a map to increase access performance.

   122  *

   123  * @note If the specified map is not a hash map, the behavior is undefined.

   124  *

   125  * @param map the map to rehash

   126  * @return zero on success, non-zero if a memory allocation error occurred

   127  */

   128 __attribute__((__nonnull__))

   129 int cxMapRehash(CxMap *map);

   132 #ifdef __cplusplus

   133 } // extern "C"

   134 #endif

   136 #endif // UCX_HASH_MAP_H

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