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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@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.