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