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 | |