ucx: src/cx/hash_map.h@d7f0b5a9a985

     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 map.h

    30  * \brief Interface for map implementations.

    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 a key within a hash map. */

    47 struct cx_hash_map_key_s {

    48     /** The key data. */

    49     CxDataPtr data;

    50     /** The hash value of the key data. */

    51     unsigned hash;

    52 };

    54 /** Internal structure for an element of a hash map. */

    55 struct cx_hash_map_element_s {

    56     /** The value data. */

    57     void *data;

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

    60     struct cx_hash_map_element_s *next;

    62     /** The corresponding key. */

    63     struct cx_hash_map_key_s key;

    64 };

    67 /**

    68  * Creates a new hash map with the specified size using a UcxAllocator.

    69  *

    70  * @param allocator the allocator to use

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

    72  * @return a pointer to the new hash map

    73  */

    74 CxMap *cxHashMapCreate(

    75         CxAllocator *allocator,

    76         size_t buckets

    77 );

    79 /**

    80  * Increases the number of buckets, if necessary.

    81  *

    82  * The load value is \c loadFactor*buckets. If the element count exceeds the load

    83  * value, the map needs to be rehashed. Otherwise, no action is performed and

    84  * this function simply returns 0.

    85  *

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

    87  * \p bucketFactor times the number of stored items. So there is enough room for additional

    88  * elements without the need of another soon rehashing.

    89  *

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

    91  *

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

    93  *

    94  * @param map the map to rehash

    95  * @param loadFactor a percentage threshold for the load of the map

    96  * @param bucketFactor a factor for the number of buckets that shall be available after rehashing

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

    98  */

    99 __attribute__((__nonnull__))

   100 int cxMapRehash2(

   101         CxMap *map,

   102         float loadFactor,

   103         float bucketFactor

   104 );

   106 /**

   107  * Rehashes the map with load factor 0.75 and bucket factor 2.5.

   108  *

   109  * @param map the map to rehash

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

   111  * @see cxMapRehash2()

   112  */

   113 __attribute__((__nonnull__))

   114 static inline int cxMapRehash(CxMap *map) {

   115     return cxMapRehash2(map, 0.75f, 2.5f);

   116 }

   119 #ifdef __cplusplus

   120 } // extern "C"

   121 #endif

   123 #endif // UCX_HASH_MAP_H

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