xref: /illumos-gate/usr/src/lib/libc/port/gen/lfind.c (revision 7257d1b4d25bfac0c802847390e98a464fd787ac)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1988 AT&T	*/
28 /*	  All Rights Reserved  	*/
29 
30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
31 
32 /*
33  * Linear search algorithm, generalized from Knuth (6.1) Algorithm Q.
34  *
35  * This version no longer has anything to do with Knuth's Algorithm Q,
36  * which first copies the new element into the table, then looks for it.
37  * The assumption there was that the cost of checking for the end of the
38  * table before each comparison outweighed the cost of the comparison, which
39  * isn't true when an arbitrary comparison function must be called and when the
40  * copy itself takes a significant number of cycles.
41  * Actually, it has now reverted to Algorithm S, which is "simpler."
42  */
43 
44 #pragma weak _lfind = lfind
45 
46 #include "lint.h"
47 #include <stdlib.h>
48 #include <mtlib.h>
49 #include <sys/types.h>
50 #include <stdio.h>
51 #include <thread.h>
52 #include <synch.h>
53 #include <search.h>
54 
55 void *
56 lfind(const void *ky, const void *bs, size_t *nelp,
57 	size_t width, int (*compar)())
58 {
59 	char *key = (char *)ky;
60 	char *base = (char *)bs;
61 	char *next = base + *nelp * width;	/* End of table */
62 
63 	for (; base < next; base += width)
64 		if ((*compar)(key, base) == 0)
65 			return (base);	/* Key found */
66 	return (NULL);
67 }
68