| | 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 | } |
projects / apple / libc.git / blame_incremental