xref: /titanic_50/usr/src/lib/libbc/libc/gen/common/bsearch.c (revision 7c478bd95313f5f23a4c958a745db2134aa03244)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 (c) 1984 AT&T */
/*        All Rights Reserved   */

#pragma ident	"%Z%%M%	%I%	%E% SMI"  /* from S5R2 1.5 */

/*LINTLIBRARY*/
/*
 * Binary search algorithm, generalized from Knuth (6.2.1) Algorithm B.
 *
 */

typedef char *POINTER;

POINTER
bsearch(key, base, nel, width, compar)
POINTER	key;			/* Key to be located */
POINTER	base;			/* Beginning of table */
unsigned nel;			/* Number of elements in the table */
unsigned width;			/* Width of an element (bytes) */
int	(*compar)();		/* Comparison function */
{
	int two_width = width + width;
	POINTER last = base + width * (nel - 1); /* Last element in table */

	while (last >= base) {

		register POINTER p = base + width * ((last - base)/two_width);
		register int res = (*compar)(key, p);

		if (res == 0)
			return (p);	/* Key found */
		if (res < 0)
			last = p - width;
		else
			base = p + width;
	}
	return ((POINTER) 0);		/* Key not found */
}