| 1 | /*␊ |
| 2 | * Copyright (c) 1990, 1993␊ |
| 3 | *␉The Regents of the University of California. All rights reserved.␊ |
| 4 | *␊ |
| 5 | * Redistribution and use in source and binary forms, with or without␊ |
| 6 | * modification, are permitted provided that the following conditions␊ |
| 7 | * are met:␊ |
| 8 | * 1. Redistributions of source code must retain the above copyright␊ |
| 9 | * notice, this list of conditions and the following disclaimer.␊ |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright␊ |
| 11 | * notice, this list of conditions and the following disclaimer in the␊ |
| 12 | * documentation and/or other materials provided with the distribution.␊ |
| 13 | * 4. Neither the name of the University nor the names of its contributors␊ |
| 14 | * may be used to endorse or promote products derived from this software␊ |
| 15 | * without specific prior written permission.␊ |
| 16 | *␊ |
| 17 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND␊ |
| 18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE␊ |
| 19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE␊ |
| 20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE␊ |
| 21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL␊ |
| 22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS␊ |
| 23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)␊ |
| 24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT␊ |
| 25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY␊ |
| 26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF␊ |
| 27 | * SUCH DAMAGE.␊ |
| 28 | */␊ |
| 29 | ␊ |
| 30 | #if defined(LIBC_SCCS) && !defined(lint)␊ |
| 31 | static char sccsid[] = "@(#)bsearch.c␉8.1 (Berkeley) 6/4/93";␊ |
| 32 | #endif /* LIBC_SCCS and not lint */␊ |
| 33 | #include <sys/cdefs.h>␊ |
| 34 | __FBSDID("$FreeBSD: src/lib/libc/stdlib/bsearch.c,v 1.4 2007/01/09 00:28:09 imp Exp $");␊ |
| 35 | ␊ |
| 36 | #include <stddef.h>␊ |
| 37 | #include <stdlib.h>␊ |
| 38 | ␊ |
| 39 | /*␊ |
| 40 | * Perform a binary search.␊ |
| 41 | *␊ |
| 42 | * The code below is a bit sneaky. After a comparison fails, we␊ |
| 43 | * divide the work in half by moving either left or right. If lim␊ |
| 44 | * is odd, moving left simply involves halving lim: e.g., when lim␊ |
| 45 | * is 5 we look at item 2, so we change lim to 2 so that we will␊ |
| 46 | * look at items 0 & 1. If lim is even, the same applies. If lim␊ |
| 47 | * is odd, moving right again involes halving lim, this time moving␊ |
| 48 | * the base up one item past p: e.g., when lim is 5 we change base␊ |
| 49 | * to item 3 and make lim 2 so that we will look at items 3 and 4.␊ |
| 50 | * If lim is even, however, we have to shrink it by one before␊ |
| 51 | * halving: e.g., when lim is 4, we still looked at item 2, so we␊ |
| 52 | * have to make lim 3, then halve, obtaining 1, so that we will only␊ |
| 53 | * look at item 3.␊ |
| 54 | */␊ |
| 55 | void *␊ |
| 56 | bsearch(key, base0, nmemb, size, compar)␊ |
| 57 | ␉const void *key;␊ |
| 58 | ␉const void *base0;␊ |
| 59 | ␉size_t nmemb;␊ |
| 60 | ␉size_t size;␊ |
| 61 | ␉int (*compar)(const void *, const void *);␊ |
| 62 | {␊ |
| 63 | ␉const char *base = base0;␊ |
| 64 | ␉size_t lim;␊ |
| 65 | ␉int cmp;␊ |
| 66 | ␉const void *p;␊ |
| 67 | ␊ |
| 68 | ␉for (lim = nmemb; lim != 0; lim >>= 1) {␊ |
| 69 | ␉␉p = base + (lim >> 1) * size;␊ |
| 70 | ␉␉cmp = (*compar)(key, p);␊ |
| 71 | ␉␉if (cmp == 0)␊ |
| 72 | ␉␉␉return ((void *)p);␊ |
| 73 | ␉␉if (cmp > 0) {␉/* key > p: move right */␊ |
| 74 | ␉␉␉base = (char *)p + size;␊ |
| 75 | ␉␉␉lim--;␊ |
| 76 | ␉␉}␉␉/* else move left */␊ |
| 77 | ␉}␊ |
| 78 | ␉return (NULL);␊ |
| 79 | }␊ |
| 80 | ␊ |
| 81 | #ifdef __BLOCKS__␊ |
| 82 | void *␊ |
| 83 | bsearch_b(key, base0, nmemb, size, compar)␊ |
| 84 | ␉const void *key;␊ |
| 85 | ␉const void *base0;␊ |
| 86 | ␉size_t nmemb;␊ |
| 87 | ␉size_t size;␊ |
| 88 | ␉int (^compar)(const void *, const void *);␊ |
| 89 | {␊ |
| 90 | ␉const char *base = base0;␊ |
| 91 | ␉size_t lim;␊ |
| 92 | ␉int cmp;␊ |
| 93 | ␉const void *p;␊ |
| 94 | ␊ |
| 95 | ␉for (lim = nmemb; lim != 0; lim >>= 1) {␊ |
| 96 | ␉␉p = base + (lim >> 1) * size;␊ |
| 97 | ␉␉cmp = compar(key, p);␊ |
| 98 | ␉␉if (cmp == 0)␊ |
| 99 | ␉␉␉return ((void *)p);␊ |
| 100 | ␉␉if (cmp > 0) {␉/* key > p: move right */␊ |
| 101 | ␉␉␉base = (char *)p + size;␊ |
| 102 | ␉␉␉lim--;␊ |
| 103 | ␉␉}␉␉/* else move left */␊ |
| 104 | ␉}␊ |
| 105 | ␉return (NULL);␊ |
| 106 | }␊ |
| 107 | #endif /* __BLOCKS__ */␊ |
| 108 | |
