usr/src/lib/libc/port/gen/lfind.c

   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 }