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      1 /*
      2  * Copyright  2008 Intel Corporation
      3  *
      4  * Permission is hereby granted, free of charge, to any person obtaining a
      5  * copy of this software and associated documentation files (the "Software"),
      6  * to deal in the Software without restriction, including without limitation
      7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      8  * and/or sell copies of the Software, and to permit persons to whom the
      9  * Software is furnished to do so, subject to the following conditions:
     10  *
     11  * The above copyright notice and this permission notice (including the next
     12  * paragraph) shall be included in all copies or substantial portions of the
     13  * Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     21  * DEALINGS IN THE SOFTWARE.
     22  */
     23 
     24 /**
     25  * \file hash_table.h
     26  * \brief Implementation of a generic, opaque hash table data type.
     27  *
     28  * \author Ian Romanick <ian.d.romanick (at) intel.com>
     29  */
     30 
     31 #ifndef HASH_TABLE_H
     32 #define HASH_TABLE_H
     33 
     34 struct hash_table;
     35 
     36 typedef unsigned (*hash_func_t)(const void *key);
     37 typedef int (*hash_compare_func_t)(const void *key1, const void *key2);
     38 
     39 #ifdef __cplusplus
     40 extern "C" {
     41 #endif
     42 
     43 /**
     44  * Hash table constructor
     45  *
     46  * Creates a hash table with the specified number of buckets.  The supplied
     47  * \c hash and \c compare routines are used when adding elements to the table
     48  * and when searching for elements in the table.
     49  *
     50  * \param num_buckets  Number of buckets (bins) in the hash table.
     51  * \param hash         Function used to compute hash value of input keys.
     52  * \param compare      Function used to compare keys.
     53  */
     54 extern struct hash_table *hash_table_ctor(unsigned num_buckets,
     55     hash_func_t hash, hash_compare_func_t compare);
     56 
     57 
     58 /**
     59  * Release all memory associated with a hash table
     60  *
     61  * \warning
     62  * This function cannot release memory occupied either by keys or data.
     63  */
     64 extern void hash_table_dtor(struct hash_table *ht);
     65 
     66 
     67 /**
     68  * Flush all entries from a hash table
     69  *
     70  * \param ht  Table to be cleared of its entries.
     71  */
     72 extern void hash_table_clear(struct hash_table *ht);
     73 
     74 
     75 /**
     76  * Search a hash table for a specific element
     77  *
     78  * \param ht   Table to be searched
     79  * \param key  Key of the desired element
     80  *
     81  * \return
     82  * The \c data value supplied to \c hash_table_insert when the element with
     83  * the matching key was added.  If no matching key exists in the table,
     84  * \c NULL is returned.
     85  */
     86 extern void *hash_table_find(struct hash_table *ht, const void *key);
     87 
     88 
     89 /**
     90  * Add an element to a hash table
     91  */
     92 extern void hash_table_insert(struct hash_table *ht, void *data,
     93     const void *key);
     94 
     95 /**
     96  * Remove a specific element from a hash table.
     97  */
     98 extern void hash_table_remove(struct hash_table *ht, const void *key);
     99 
    100 /**
    101  * Compute hash value of a string
    102  *
    103  * Computes the hash value of a string using the DJB2 algorithm developed by
    104  * Professor Daniel J. Bernstein.  It was published on comp.lang.c once upon
    105  * a time.  I was unable to find the original posting in the archives.
    106  *
    107  * \param key  Pointer to a NUL terminated string to be hashed.
    108  *
    109  * \sa hash_table_string_compare
    110  */
    111 extern unsigned hash_table_string_hash(const void *key);
    112 
    113 
    114 /**
    115  * Compare two strings used as keys
    116  *
    117  * This is just a macro wrapper around \c strcmp.
    118  *
    119  * \sa hash_table_string_hash
    120  */
    121 #define hash_table_string_compare ((hash_compare_func_t) strcmp)
    122 
    123 
    124 /**
    125  * Compute hash value of a pointer
    126  *
    127  * \param key  Pointer to be used as a hash key
    128  *
    129  * \note
    130  * The memory pointed to by \c key is \b never accessed.  The value of \c key
    131  * itself is used as the hash key
    132  *
    133  * \sa hash_table_pointer_compare
    134  */
    135 unsigned
    136 hash_table_pointer_hash(const void *key);
    137 
    138 
    139 /**
    140  * Compare two pointers used as keys
    141  *
    142  * \sa hash_table_pointer_hash
    143  */
    144 int
    145 hash_table_pointer_compare(const void *key1, const void *key2);
    146 
    147 #ifdef __cplusplus
    148 }
    149 #endif
    150 #endif /* HASH_TABLE_H */
    151