ucx: src/cx/hash_map.h@fd3368c20413

     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 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     unsigned char *data;

    50     /**

    51      * The key data length.

    52      */

    53     size_t len;

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

    55     unsigned hash;

    56 };

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

    59 struct cx_hash_map_element_s {

    60     /** The value data. */

    61     void *data;

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

    64     struct cx_hash_map_element_s *next;

    66     /** The corresponding key. */

    67     struct cx_hash_map_key_s key;

    68 };

    70 /**

    71  * Internal structure for a hash map.

    72  */

    73 struct cx_hash_map_s {

    74     /**

    75      * Base structure for maps.

    76      */

    77     struct cx_map_s base;

    78     /**

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

    80      */

    81     struct cx_hash_map_element_s **buckets;

    82     /**

    83      * The number of buckets.

    84      */

    85     size_t bucket_count;

    86 };

    89 /**

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

    91  *

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

    93  *

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

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

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

    97  *

    98  * @param allocator the allocator to use

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

   100  * @return a pointer to the new hash map

   101  */

   102 __attribute__((__nonnull__, __warn_unused_result__))

   103 CxMap *cxHashMapCreate(

   104         CxAllocator *allocator,

   105         size_t buckets

   106 );

   108 /**

   109  * Increases the number of buckets, if necessary.

   110  *

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

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

   113  * this function simply returns 0.

   114  *

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

   116  * 2.5 times the element count. So there is enough room for additional

   117  * elements without the need of another soon rehashing.

   118  *

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

   120  *

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

   122  *

   123  * @param map the map to rehash

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

   125  */

   126 __attribute__((__nonnull__))

   127 int cxMapRehash(CxMap *map);

   130 #ifdef __cplusplus

   131 } // extern "C"

   132 #endif

   134 #endif // UCX_HASH_MAP_H

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