1/* 2 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved. 3 * 4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. The rights granted to you under the License 10 * may not be used to create, or enable the creation or redistribution of, 11 * unlawful or unlicensed copies of an Apple operating system, or to 12 * circumvent, violate, or enable the circumvention or violation of, any 13 * terms of an Apple operating system software license agreement. 14 * 15 * Please obtain a copy of the License at 16 * http://www.opensource.apple.com/apsl/ and read it before using this file. 17 * 18 * The Original Code and all software distributed under the License are 19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 23 * Please see the License for the specific language governing rights and 24 * limitations under the License. 25 * 26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ 27 */ 28/* 29 * Copyright (c) 1990, 1993 30 * The Regents of the University of California. All rights reserved. 31 * 32 * Redistribution and use in source and binary forms, with or without 33 * modification, are permitted provided that the following conditions 34 * are met: 35 * 1. Redistributions of source code must retain the above copyright 36 * notice, this list of conditions and the following disclaimer. 37 * 2. Redistributions in binary form must reproduce the above copyright 38 * notice, this list of conditions and the following disclaimer in the 39 * documentation and/or other materials provided with the distribution. 40 * 3. All advertising materials mentioning features or use of this software 41 * must display the following acknowledgement: 42 * This product includes software developed by the University of 43 * California, Berkeley and its contributors. 44 * 4. Neither the name of the University nor the names of its contributors 45 * may be used to endorse or promote products derived from this software 46 * without specific prior written permission. 47 * 48 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 49 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 50 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 51 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 52 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 53 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 54 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 55 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 56 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 57 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 58 * SUCH DAMAGE. 59 */ 60 61#if defined(LIBC_SCCS) && !defined(lint) 62static char sccsid[] = "@(#)bsearch.c 8.1 (Berkeley) 6/4/93"; 63#endif /* LIBC_SCCS and not lint */ 64 65#include <libsa/stdlib.h> 66 67/* 68 * Perform a binary search. 69 * 70 * The code below is a bit sneaky. After a comparison fails, we 71 * divide the work in half by moving either left or right. If lim 72 * is odd, moving left simply involves halving lim: e.g., when lim 73 * is 5 we look at item 2, so we change lim to 2 so that we will 74 * look at items 0 & 1. If lim is even, the same applies. If lim 75 * is odd, moving right again involes halving lim, this time moving 76 * the base up one item past p: e.g., when lim is 5 we change base 77 * to item 3 and make lim 2 so that we will look at items 3 and 4. 78 * If lim is even, however, we have to shrink it by one before 79 * halving: e.g., when lim is 4, we still looked at item 2, so we 80 * have to make lim 3, then halve, obtaining 1, so that we will only 81 * look at item 3. 82 */ 83__private_extern__ 84const void * bsearch( 85 register const void *key, 86 const void *base0, 87 size_t nmemb, 88 register size_t size, 89 register int (*compar)(const void *, const void *)) { 90 91 register const char *base = base0; 92 register size_t lim; 93 register int cmp; 94 register const void *p; 95 96 for (lim = nmemb; lim != 0; lim >>= 1) { 97 p = base + (lim >> 1) * size; 98 cmp = (*compar)(key, p); 99 if (cmp == 0) 100 return p; 101 if (cmp > 0) { /* key > p: move right */ 102 base = (const char *)p + size; 103 lim--; 104 } /* else move left */ 105 } 106 return (NULL); 107} 108