source: mainline/uspace/lib/c/generic/adt/hash_table.c@ 892022a1

/*
 * Copyright (c) 2008 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.
 */

/** @addtogroup libc
 * @{
 */
/** @file
 */

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

#include <adt/hash_table.h>
#include <adt/list.h>
#include <unistd.h>
#include <malloc.h>
#include <assert.h>
#include <str.h>

/** Create chained hash table.
 *
 * @param h        Hash table structure. Will be initialized by this call.
 * @param m        Number of hash table buckets.
 * @param max_keys Maximal number of keys needed to identify an item.
 * @param op       Hash table operations structure.
 *
 * @return True on success
 *
 */
bool hash_table_create(hash_table_t *h, hash_count_t m, hash_count_t max_keys,
    hash_table_operations_t *op)
{
        assert(h);
        assert(op && op->hash && op->compare);
        assert(max_keys > 0);
        
        h->entry = malloc(m * sizeof(list_t));
        if (!h->entry)
                return false;
        
        memset((void *) h->entry, 0,  m * sizeof(list_t));
        
        hash_count_t i;
        for (i = 0; i < m; i++)
                list_initialize(&h->entry[i]);
        
        h->entries = m;
        h->max_keys = max_keys;
        h->op = op;
        
        return true;
}

/** Remove all elements from the hash table
 *
 * @param h Hash table to be cleared
 */
void hash_table_clear(hash_table_t *h)
{
        for (hash_count_t chain = 0; chain < h->entries; ++chain) {
                link_t *cur;
                link_t *next;
                
                for (cur = h->entry[chain].head.next;
                    cur != &h->entry[chain].head;
                    cur = next) {
                        next = cur->next;
                        list_remove(cur);
                        h->op->remove_callback(cur);
                }
        }
}

/** Destroy a hash table instance.
 *
 * @param h Hash table to be destroyed.
 *
 */
void hash_table_destroy(hash_table_t *h)
{
        assert(h);
        assert(h->entry);
        
        free(h->entry);
}

/** Insert item into a hash table.
 *
 * @param h    Hash table.
 * @param key  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)
{
        assert(item);
        assert(h && h->op && h->op->hash && h->op->compare);
        
        hash_index_t 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[])
{
        assert(h && h->op && h->op->hash && h->op->compare);
        
        hash_index_t chain = h->op->hash(key);
        assert(chain < h->entries);
        
        list_foreach(h->entry[chain], cur) {
                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)
{
        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.
                 */
                
                link_t *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.
         */
        hash_index_t chain;
        for (chain = 0; chain < h->entries; chain++) {
                for (link_t *cur = h->entry[chain].head.next;
                    cur != &h->entry[chain].head;
                    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;
                        }
                }
        }
}

/** Apply function to all items in hash table.
 *
 * @param h   Hash table.
 * @param f   Function to be applied.
 * @param arg Argument to be passed to the function.
 *
 */
void hash_table_apply(hash_table_t *h, void (*f)(link_t *, void *), void *arg)
{       
        for (hash_index_t bucket = 0; bucket < h->entries; bucket++) {
                link_t *cur;
                link_t *next;

                for (cur = h->entry[bucket].head.next; cur != &h->entry[bucket].head;
                    cur = next) {
                        /*
                         * The next pointer must be stored prior to the functor
                         * call to allow using destructor as the functor (the
                         * free function could overwrite the cur->next pointer).
                         */
                        next = cur->next;
                        f(cur, arg);
                }
        }
}

/** @}
 */