ucx: src/cx/hash_map.h@69a83fad8a35

     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

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     8  *

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    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

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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 {

    48     /** The value data. */

    49     void *data;

    51     /** A pointer to the next element in the current bucket. */

    52     struct cx_hash_map_element_s *next;

    54     /** The corresponding key. */

    55     CxHashKey key;

    56 };

    58 /**

    59  * Internal structure for a hash map.

    60  */

    61 struct cx_hash_map_s {

    62     /**

    63      * Base structure for maps.

    64      */

    65     struct cx_map_s base;

    66     /**

    67      * The buckets of this map, each containing a linked list of elements.

    68      */

    69     struct cx_hash_map_element_s **buckets;

    70     /**

    71      * The number of buckets.

    72      */

    73     size_t bucket_count;

    74 };

    77 /**

    78  * Creates a new hash map with the specified number of buckets.

    79  *

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

    81  *

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

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

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

    85  *

    86  * @param allocator the allocator to use

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

    88  * @return a pointer to the new hash map

    89  */

    90 __attribute__((__nonnull__, __warn_unused_result__))

    91 CxMap *cxHashMapCreate(

    92         CxAllocator *allocator,

    93         size_t buckets

    94 );

    96 /**

    97  * Increases the number of buckets, if necessary.

    98  *

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

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

   101  * this function simply returns 0.

   102  *

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

   104  * 2.5 times the element count. So there is enough room for additional

   105  * elements without the need of another soon rehashing.

   106  *

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

   108  *

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

   110  *

   111  * @param map the map to rehash

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

   113  */

   114 __attribute__((__nonnull__))

   115 int cxMapRehash(CxMap *map);

   118 #ifdef __cplusplus

   119 } // extern "C"

   120 #endif

   122 #endif // UCX_HASH_MAP_H

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