ucx: src/cx/hash_key.h@1e2be40f0cb5

     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_key.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  */

    38 #ifndef UCX_HASH_KEY_H

    39 #define UCX_HASH_KEY_H

    41 #include "stddef.h"

    43 #ifdef __cplusplus

    44 extern "C" {

    45 #endif

    47 /** Internal structure for a key within a hash map. */

    48 struct cx_hash_key_s {

    49     /** The key data. */

    50     union {

    51         unsigned char *bytes;

    52         unsigned char const *cbytes;

    53         char *str;

    54         char const *cstr;

    55         void *obj;

    56         void const *cobj;

    57     } data;

    58     /**

    59      * The key data length.

    60      */

    61     size_t len;

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

    63     unsigned hash;

    64 };

    66 /**

    67  * Type for a hash key.

    68  */

    69 typedef struct cx_hash_key_s CxHashKey;

    71 /**

    72  * Computes a murmur2 32 bit hash.

    73  *

    74  * You need to initialize \c data and \c len in the key struct.

    75  * The hash is then directly written to that struct.

    76  *

    77  * \note If \c data is \c NULL, the hash is defined as 1574210520.

    78  *

    79  * @param key the key, the hash shall be computed for

    80  */

    81 void cx_hash_murmur(CxHashKey *key);

    83 /**

    84  * Computes a hash key from a string.

    85  *

    86  * The string needs to be zero-terminated.

    87  *

    88  * @param str the string

    89  * @return the hash key

    90  */

    91 __attribute__((__warn_unused_result__))

    92 CxHashKey cx_hash_key_str(char const *str);

    94 /**

    95  * Computes a hash key from a byte array.

    96  *

    97  * @param bytes the array

    98  * @param len the length

    99  * @return the hash key

   100  */

   101 __attribute__((__warn_unused_result__))

   102 CxHashKey cx_hash_key_bytes(

   103         unsigned char const *bytes,

   104         size_t len

   105 );

   107 /**

   108  * Computes a hash key for an arbitrary object.

   109  *

   110  * The computation uses the in-memory representation that might not be

   111  * the same on different platforms. Therefore, this hash should not be

   112  * used for data exchange with different machines.

   113  *

   114  * @param obj a pointer to an arbitrary object

   115  * @param len the length of object in memory

   116  * @return the hash key

   117  */

   118 __attribute__((__warn_unused_result__))

   119 CxHashKey cx_hash_key(

   120         void const *obj,

   121         size_t len

   122 );

   124 #ifdef __cplusplus

   125 } // extern "C"

   126 #endif

   128 #endif // UCX_HASH_KEY_H

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