hash.c

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/* hash.c
 
   Routines for manipulating hash tables... */
 
/*
 * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of The Internet Software Consortium nor the names
 *    of its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
 * CONTRIBUTORS ``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 INTERNET SOFTWARE CONSORTIUM OR
 * CONTRIBUTORS 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 software has been written for the Internet Software Consortium
 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
 * Enterprises.  To learn more about the Internet Software Consortium,
 * see ``http://www.vix.com/isc''.  To learn more about Vixie
 * Enterprises, see ``http://www.vix.com''.
 */
 
#define lint
#ifndef lint
static char copyright[] =
"$Id: hash.c,v 1.9.2.3 1999/04/09 17:39:41 mellon Exp $ Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.  All rights reserved.\n";
#endif /* not lint */
 
#include <rosdhcp.h>
 
static __inline int do_hash PROTO ((unsigned char *, int, int));
 
struct hash_table *new_hash ()
{
    struct hash_table *rv = new_hash_table (DEFAULT_HASH_SIZE);
    if (!rv)
        return rv;
    memset (&rv -> buckets [0], 0,
        DEFAULT_HASH_SIZE * sizeof (struct hash_bucket *));
    return rv;
}
 
static __inline int do_hash (name, len, size)
    unsigned char *name;
    int len;
    int size;
{
    register int accum = 0;
    register unsigned char *s = name;
    int i = len;
    while (i--) {
        /* Add the character in... */
        accum += *s++;
        /* Add carry back in... */
        while (accum > 255) {
            accum = (accum & 255) + (accum >> 8);
        }
    }
    return accum % size;
}
 
void add_hash (table, name, len, pointer)
    struct hash_table *table;
    int len;
    unsigned char *name;
    unsigned char *pointer;
{
    int hashno;
    struct hash_bucket *bp;
 
    if (!table)
        return;
    if (!len)
        len = strlen ((char *)name);
 
    hashno = do_hash (name, len, table -> hash_count);
    bp = new_hash_bucket ();
 
    if (!bp) {
        warn ("Can't add %s to hash table.", name);
        return;
    }
    bp -> name = name;
    bp -> value = pointer;
    bp -> next = table -> buckets [hashno];
    bp -> len = len;
    table -> buckets [hashno] = bp;
}
 
void delete_hash_entry (table, name, len)
    struct hash_table *table;
    int len;
    unsigned char *name;
{
    int hashno;
    struct hash_bucket *bp, *pbp = (struct hash_bucket *)0;
 
    if (!table)
        return;
    if (!len)
        len = strlen ((char *)name);
 
    hashno = do_hash (name, len, table -> hash_count);
 
    /* Go through the list looking for an entry that matches;
       if we find it, delete it. */
    for (bp = table -> buckets [hashno]; bp; bp = bp -> next) {
        if ((!bp -> len &&
             !strcmp ((char *)bp -> name, (char *)name)) ||
            (bp -> len == len &&
             !memcmp (bp -> name, name, len))) {
            if (pbp) {
                pbp -> next = bp -> next;
            } else {
                table -> buckets [hashno] = bp -> next;
            }
            free_hash_bucket (bp, "delete_hash_entry");
            break;
        }
        pbp = bp;   /* jwg, 9/6/96 - nice catch! */
    }
}
 
unsigned char *hash_lookup (table, name, len)
    struct hash_table *table;
    unsigned char *name;
    int len;
{
    int hashno;
    struct hash_bucket *bp;
 
    if (!table)
        return (unsigned char *)0;
 
    if (!len)
        len = strlen ((char *)name);
 
    hashno = do_hash (name, len, table -> hash_count);
 
    for (bp = table -> buckets [hashno]; bp; bp = bp -> next) {
        if (len == bp -> len && !memcmp (bp -> name, name, len))
            return bp -> value;
    }
    return (unsigned char *)0;
}