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  1. /*
  2.  * Copyright (c) 2006 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup libc
  30.  * @{
  31.  */
  32. /** @file
  33.  */
  34.  
  35. /*
  36.  * This is an implementation of generic chained hash table.
  37.  */
  38.  
  39. #include <libadt/hash_table.h>
  40. #include <libadt/list.h>
  41. #include <unistd.h>
  42. #include <malloc.h>
  43. #include <assert.h>
  44. #include <stdio.h>
  45. #include <string.h>
  46.  
  47. /** Create chained hash table.
  48.  *
  49.  * @param h Hash table structure. Will be initialized by this call.
  50.  * @param m Number of slots in the hash table.
  51.  * @param max_keys Maximal number of keys needed to identify an item.
  52.  * @param op Hash table operations structure.
  53.  * @return true on success
  54.  */
  55. int hash_table_create(hash_table_t *h, hash_count_t m, hash_count_t max_keys, hash_table_operations_t *op)
  56. {
  57.     hash_count_t i;
  58.  
  59.     assert(h);
  60.     assert(op && op->hash && op->compare);
  61.     assert(max_keys > 0);
  62.    
  63.     h->entry = malloc(m * sizeof(link_t));
  64.     if (!h->entry) {
  65.         printf("cannot allocate memory for hash table\n");
  66.         return false;
  67.     }
  68.     memset((void *) h->entry, 0,  m * sizeof(link_t));
  69.    
  70.     for (i = 0; i < m; i++)
  71.         list_initialize(&h->entry[i]);
  72.    
  73.     h->entries = m;
  74.     h->max_keys = max_keys;
  75.     h->op = op;
  76.     return true;
  77. }
  78.  
  79. /** Insert item into hash table.
  80.  *
  81.  * @param h Hash table.
  82.  * @param key Array of all keys necessary to compute hash index.
  83.  * @param item Item to be inserted into the hash table.
  84.  */
  85. void hash_table_insert(hash_table_t *h, unsigned long key[], link_t *item)
  86. {
  87.     hash_index_t chain;
  88.  
  89.     assert(item);
  90.     assert(h && h->op && h->op->hash && h->op->compare);
  91.  
  92.     chain = h->op->hash(key);
  93.     assert(chain < h->entries);
  94.    
  95.     list_append(item, &h->entry[chain]);
  96. }
  97.  
  98. /** Search hash table for an item matching keys.
  99.  *
  100.  * @param h Hash table.
  101.  * @param key Array of all keys needed to compute hash index.
  102.  *
  103.  * @return Matching item on success, NULL if there is no such item.
  104.  */
  105. link_t *hash_table_find(hash_table_t *h, unsigned long key[])
  106. {
  107.     link_t *cur;
  108.     hash_index_t chain;
  109.  
  110.     assert(h && h->op && h->op->hash && h->op->compare);
  111.  
  112.     chain = h->op->hash(key);
  113.     assert(chain < h->entries);
  114.    
  115.     for (cur = h->entry[chain].next; cur != &h->entry[chain]; cur = cur->next) {
  116.         if (h->op->compare(key, h->max_keys, cur)) {
  117.             /*
  118.              * The entry is there.
  119.              */
  120.             return cur;
  121.         }
  122.     }
  123.    
  124.     return NULL;
  125. }
  126.  
  127. /** Remove all matching items from hash table.
  128.  *
  129.  * For each removed item, h->remove_callback() is called.
  130.  *
  131.  * @param h Hash table.
  132.  * @param key Array of keys that will be compared against items of the hash table.
  133.  * @param keys Number of keys in the 'key' array.
  134.  */
  135. void hash_table_remove(hash_table_t *h, unsigned long key[], hash_count_t keys)
  136. {
  137.     hash_index_t chain;
  138.     link_t *cur;
  139.  
  140.     assert(h && h->op && h->op->hash && h->op->compare && h->op->remove_callback);
  141.     assert(keys <= h->max_keys);
  142.    
  143.     if (keys == h->max_keys) {
  144.  
  145.         /*
  146.          * All keys are known, hash_table_find() can be used to find the entry.
  147.          */
  148.    
  149.         cur = hash_table_find(h, key);
  150.         if (cur) {
  151.             list_remove(cur);
  152.             h->op->remove_callback(cur);
  153.         }
  154.         return;
  155.     }
  156.    
  157.     /*
  158.      * Fewer keys were passed.
  159.      * Any partially matching entries are to be removed.
  160.      */
  161.     for (chain = 0; chain < h->entries; chain++) {
  162.         for (cur = h->entry[chain].next; cur != &h->entry[chain]; cur = cur->next) {
  163.             if (h->op->compare(key, keys, cur)) {
  164.                 link_t *hlp;
  165.                
  166.                 hlp = cur;
  167.                 cur = cur->prev;
  168.                
  169.                 list_remove(hlp);
  170.                 h->op->remove_callback(hlp);
  171.                
  172.                 continue;
  173.             }
  174.         }
  175.     }
  176. }
  177.  
  178. /** @}
  179.  */
  180.