lsearch.c

早期freebsd实现

/*
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Roger L. Snyder.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)lsearch.c	8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>
#include <unistd.h>

static char *linear_base();

char *
lsearch(key, base, nelp, width, compar)
	char *key, *base;
	u_int *nelp, width;
	int (*compar)();
{
	return(linear_base(key, base, nelp, width, compar, 1));
}

char *
lfind(key, base, nelp, width, compar)
	char *key, *base;
	u_int *nelp, width;
	int (*compar)();
{
	return(linear_base(key, base, nelp, width, compar, 0));
}

static char *
linear_base(key, base, nelp, width, compar, add_flag)
	char *key, *base;
	u_int *nelp, width;
	int (*compar)(), add_flag;
{
	register char *element, *end;

	end = base + *nelp * width;
	for (element = base; element < end; element += width)
		if (!compar(element, key))		/* key found */
			return(element);

	if (!add_flag)					/* key not found */
		return(NULL);

	/*
	 * The UNIX System User's Manual, 1986 edition claims that
	 * a NULL pointer is returned by lsearch with errno set
	 * appropriately, if there is not enough room in the table
	 * to add a new item.  This can't be done as none of these
	 * routines have any method of determining the size of the
	 * table.  This comment was isn't in the 1986-87 System V
	 * manual.
	 */
	++*nelp;
	bcopy(key, end, (int)width);
	return(end);
}