usr/src/lib/libbc/libc/gen/common/lsearch.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, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*      Copyright (c) 1984 AT&T */
  23 /*        All Rights Reserved   */
  24
  25 #pragma ident   "%Z%%M% %I%     %E% SMI"  /* from S5R2 1.8 */
  26
  27 /*LINTLIBRARY*/
  28 /*
  29  * Linear search algorithm, generalized from Knuth (6.1) Algorithm Q.
  30  *
  31  * This version no longer has anything to do with Knuth's Algorithm Q,
  32  * which first copies the new element into the table, then looks for it.
  33  * The assumption there was that the cost of checking for the end of the
  34  * table before each comparison outweighed the cost of the comparison, which
  35  * isn't true when an arbitrary comparison function must be called and when the
  36  * copy itself takes a significant number of cycles.
  37  * Actually, it has now reverted to Algorithm S, which is "simpler."
  38  */
  39
  40 typedef char *POINTER;
  41 extern POINTER memcpy();
  42
  43 POINTER
  44 lsearch(key, base, nelp, width, compar)
  45 register POINTER key;           /* Key to be located */
  46 register POINTER base;          /* Beginning of table */
  47 unsigned *nelp;                 /* Pointer to current table size */
  48 register unsigned width;        /* Width of an element (bytes) */
  49 int (*compar)();                /* Comparison function */
  50 {
  51         register POINTER next = base + *nelp * width;   /* End of table */
  52
  53         for ( ; base < next; base += width)
  54                 if ((*compar)(key, base) == 0)
  55                         return (base);  /* Key found */
  56         ++*nelp;                        /* Not found, add to table */
  57         return (memcpy(base, key, (int)width)); /* base now == next */
  58 }