libnsctl/common/hash.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <string.h>
#include <stdlib.h>
#include <sys/nsctl/nsc_hash.h>

#define HASH_PRIME 2039

static int calc_hash(const char *);

hash_node_t **
nsc_create_hash()
{
    hash_node_t **hash;

    hash = (hash_node_t **)calloc(HASH_PRIME, sizeof (hash_node_t *));
    return (hash);
}

int
nsc_insert_node(hash_node_t **hash, void *data, const char *key)
{
    int index;
    hash_node_t *node;

    node = (hash_node_t *)malloc(sizeof (hash_node_t));
    if (!node) {
        return (-1);
    }
    node->key = strdup(key);
    node->data = data;

    /*
     * possible enhancement would be to search
     * in this index for a duplicate
     */
    index = calc_hash(key);
    node->next = hash[ index ];
    hash[ index ] = node;

    return (0);
}

/*
 * lookup
 *
 * Description:
 *  Searches the hash to find a node.
 *
 * Return values:
 *  0 if not found.
 *  pointer to node if found.
 */
void *
nsc_lookup(hash_node_t **hash, const char *key)
{
    int index;
    hash_node_t *node;

    index = calc_hash(key);
    node = hash[ index ];
    while (node) {
        if (strcmp(node->key, key) == 0)
            return (node->data);
        node = node->next;
    }
    return (0);
}

void *
nsc_remove_node(hash_node_t **hash, char *key)
{
    int index;
    hash_node_t *node, *prev;
    void *retval;

    index = calc_hash(key);
    if (!hash[ index ]) {
        return (0);
    }

    if (strcmp(hash[ index ]->key, key) == 0) {
        node = hash[ index ];
        retval = node->data;
        hash[ index ] = hash[ index ]->next;
        free(node->key);
        free(node);
        return (retval);
    }
    prev = hash[ index ];
    node = prev->next;
    while (node && (strcmp(node->key, key) != 0)) {
        prev = node;
        node = node->next;
    }

    /* did we find it? */
    if (node) {
        prev->next = node->next;
        retval = node->data;
        free(node->key);
        free(node);
        return (retval);
    }
    return (0);
}

void
nsc_remove_all(hash_node_t **hash, void (*callback)(void *))
{
    int i;
    hash_node_t *p, *next;

    for (i = 0; i < HASH_PRIME; i++) {
        p = hash[ i ];
        while (p) {
            next = p->next;
            if (callback) {
                callback(p->data);
            }
            free(p->key);
            free(p);
            p = next;
        }
    }
    free(hash);
}

/* ---------------------------------------------------------------------- */

/*
 * Basic rotating hash, as per Knuth.
 */
static int
calc_hash(const char *key)
{
    unsigned int hash, i;
    int len = strlen(key);
    for (hash = len, i = 0; i < len; i++) {
        hash = (hash << 5) ^ (hash >> 27) ^ key[ i ];
    }
    return (hash % HASH_PRIME);
}