source: mainline/libadt/generic/hash_table.c@ 4f34b6a

/*
 * Copyright (C) 2006 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This is an implementation of generic chained hash table.
 */

#include <hash_table.h>
#include <list.h>
#include <unistd.h>
#include <malloc.h>
#include <assert.h>
#include <stdio.h>
#include <string.h>

/** Create chained hash table.
 *
 * @param h Hash table structure. Will be initialized by this call.
 * @param m Number of slots in the hash table.
 * @param max_keys Maximal number of keys needed to identify an item.
 * @param op Hash table operations structure.
 * @return true on success
 */
int hash_table_create(hash_table_t *h, hash_count_t m, hash_count_t max_keys, hash_table_operations_t *op)
{
        hash_count_t i;

        assert(h);
        assert(op && op->hash && op->compare);
        assert(max_keys > 0);
        
        h->entry = malloc(m * sizeof(link_t *));
        if (!h->entry) {
                printf("cannot allocate memory for hash table\n");
                return false;
        }
        memset((void *) h->entry, 0,  m * sizeof(link_t *));
        
        for (i = 0; i < m; i++)
                list_initialize(&h->entry[i]);
        
        h->entries = m;
        h->max_keys = max_keys;
        h->op = op;
        return true;
}

/** Insert item into hash table.
 *
 * @param h Hash table.
 * @param hey Array of all keys necessary to compute hash index.
 * @param item Item to be inserted into the hash table.
 */
void hash_table_insert(hash_table_t *h, unsigned long key[], link_t *item)
{
        hash_index_t chain;

        assert(item);
        assert(h && h->op && h->op->hash && h->op->compare);

        chain = h->op->hash(key);
        assert(chain < h->entries);
        
        list_append(item, &h->entry[chain]);
}

/** Search hash table for an item matching keys.
 *
 * @param h Hash table.
 * @param key Array of all keys needed to compute hash index.
 *
 * @return Matching item on success, NULL if there is no such item.
 */
link_t *hash_table_find(hash_table_t *h, unsigned long key[])
{
        link_t *cur;
        hash_index_t chain;

        assert(h && h->op && h->op->hash && h->op->compare);

        chain = h->op->hash(key);
        assert(chain < h->entries);
        
        /*
         * The hash table is not redundant.
         * Check if the keys are not in place already.
         */
        for (cur = h->entry[chain].next; cur != &h->entry[chain]; cur = cur->next) {
                if (h->op->compare(key, h->max_keys, cur)) {
                        /*
                         * The entry is there.
                         */
                        return cur;
                }
        }
        
        return NULL;
}

/** Remove all matching items from hash table.
 *
 * For each removed item, h->remove_callback() is called.
 *
 * @param h Hash table.
 * @param key Array of keys that will be compared against items of the hash table.
 * @param keys Number of keys in the 'key' array.
 */
void hash_table_remove(hash_table_t *h, unsigned long key[], hash_count_t keys)
{
        hash_index_t chain;
        link_t *cur;

        assert(h && h->op && h->op->hash && h->op->compare && h->op->remove_callback);
        assert(keys <= h->max_keys);
        
        if (keys == h->max_keys) {

                /*
                 * All keys are known, hash_table_find() can be used to find the entry.
                 */
        
                cur = hash_table_find(h, key);
                if (cur) {
                        list_remove(cur);
                        h->op->remove_callback(cur);
                }
                return;
        }
        
        /*
         * Fewer keys were passed.
         * Any partially matching entries are to be removed.
         */
        for (chain = 0; chain < h->entries; chain++) {
                for (cur = h->entry[chain].next; cur != &h->entry[chain]; cur = cur->next) {
                        if (h->op->compare(key, keys, cur)) {
                                link_t *hlp;
                                
                                hlp = cur;
                                cur = cur->prev;
                                
                                list_remove(hlp);
                                h->op->remove_callback(hlp);
                                
                                continue;
                        }
                }
        }
}