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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. /*
  30.  * This is an implementation of generic chained hash table.
  31.  */
  32.  
  33. #include <hash_table.h>
  34. #include <list.h>
  35. #include <unistd.h>
  36. #include <malloc.h>
  37. #include <assert.h>
  38. #include <stdio.h>
  39. #include <string.h>
  40.  
  41. /** Create chained hash table.
  42.  *
  43.  * @param h Hash table structure. Will be initialized by this call.
  44.  * @param m Number of slots in the hash table.
  45.  * @param max_keys Maximal number of keys needed to identify an item.
  46.  * @param op Hash table operations structure.
  47.  * @return true on success
  48.  */
  49. int hash_table_create(hash_table_t *h, hash_count_t m, hash_count_t max_keys, hash_table_operations_t *op)
  50. {
  51.     hash_count_t i;
  52.  
  53.     assert(h);
  54.     assert(op && op->hash && op->compare);
  55.     assert(max_keys > 0);
  56.    
  57.     h->entry = malloc(m * sizeof(link_t));
  58.     if (!h->entry) {
  59.         printf("cannot allocate memory for hash table\n");
  60.         return false;
  61.     }
  62.     memset((void *) h->entry, 0,  m * sizeof(link_t));
  63.    
  64.     for (i = 0; i < m; i++)
  65.         list_initialize(&h->entry[i]);
  66.    
  67.     h->entries = m;
  68.     h->max_keys = max_keys;
  69.     h->op = op;
  70.     return true;
  71. }
  72.  
  73. /** Insert item into hash table.
  74.  *
  75.  * @param h Hash table.
  76.  * @param hey Array of all keys necessary to compute hash index.
  77.  * @param item Item to be inserted into the hash table.
  78.  */
  79. void hash_table_insert(hash_table_t *h, unsigned long key[], link_t *item)
  80. {
  81.     hash_index_t chain;
  82.  
  83.     assert(item);
  84.     assert(h && h->op && h->op->hash && h->op->compare);
  85.  
  86.     chain = h->op->hash(key);
  87.     assert(chain < h->entries);
  88.    
  89.     list_append(item, &h->entry[chain]);
  90. }
  91.  
  92. /** Search hash table for an item matching keys.
  93.  *
  94.  * @param h Hash table.
  95.  * @param key Array of all keys needed to compute hash index.
  96.  *
  97.  * @return Matching item on success, NULL if there is no such item.
  98.  */
  99. link_t *hash_table_find(hash_table_t *h, unsigned long key[])
  100. {
  101.     link_t *cur;
  102.     hash_index_t chain;
  103.  
  104.     assert(h && h->op && h->op->hash && h->op->compare);
  105.  
  106.     chain = h->op->hash(key);
  107.     assert(chain < h->entries);
  108.    
  109.     /*
  110.      * The hash table is not redundant.
  111.      * Check if the keys are not in place already.
  112.      */
  113.     for (cur = h->entry[chain].next; cur != &h->entry[chain]; cur = cur->next) {
  114.         if (h->op->compare(key, h->max_keys, cur)) {
  115.             /*
  116.              * The entry is there.
  117.              */
  118.             return cur;
  119.         }
  120.     }
  121.    
  122.     return NULL;
  123. }
  124.  
  125. /** Remove all matching items from hash table.
  126.  *
  127.  * For each removed item, h->remove_callback() is called.
  128.  *
  129.  * @param h Hash table.
  130.  * @param key Array of keys that will be compared against items of the hash table.
  131.  * @param keys Number of keys in the 'key' array.
  132.  */
  133. void hash_table_remove(hash_table_t *h, unsigned long key[], hash_count_t keys)
  134. {
  135.     hash_index_t chain;
  136.     link_t *cur;
  137.  
  138.     assert(h && h->op && h->op->hash && h->op->compare && h->op->remove_callback);
  139.     assert(keys <= h->max_keys);
  140.    
  141.     if (keys == h->max_keys) {
  142.  
  143.         /*
  144.          * All keys are known, hash_table_find() can be used to find the entry.
  145.          */
  146.    
  147.         cur = hash_table_find(h, key);
  148.         if (cur) {
  149.             list_remove(cur);
  150.             h->op->remove_callback(cur);
  151.         }
  152.         return;
  153.     }
  154.    
  155.     /*
  156.      * Fewer keys were passed.
  157.      * Any partially matching entries are to be removed.
  158.      */
  159.     for (chain = 0; chain < h->entries; chain++) {
  160.         for (cur = h->entry[chain].next; cur != &h->entry[chain]; cur = cur->next) {
  161.             if (h->op->compare(key, keys, cur)) {
  162.                 link_t *hlp;
  163.                
  164.                 hlp = cur;
  165.                 cur = cur->prev;
  166.                
  167.                 list_remove(hlp);
  168.                 h->op->remove_callback(hlp);
  169.                
  170.                 continue;
  171.             }
  172.         }
  173.     }
  174. }
  175.