Mercurial > hg > CbC > CbC_gcc

comparison libiberty/bsearch.c @ 0:a06113de4d67

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
first commit
author kent <kent@cr.ie.u-ryukyu.ac.jp>
date Fri, 17 Jul 2009 14:47:48 +0900
parents
children f6334be47118
comparison
equal deleted inserted replaced
-1:000000000000 0:a06113de4d67
1 /*
2 * Copyright (c) 1990 Regents of the University of California.
3 * 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 * 3. [rescinded 22 July 1999]
14 * 4. Neither the name of the University nor the names of its contributors
15 * may be used to endorse or promote products derived from this software
16 * without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31 /*
32
33 @deftypefn Supplemental void* bsearch (const void *@var{key}, const void *@var{base}, size_t @var{nmemb}, size_t @var{size}, int (*@var{compar})(const void *, const void *))
34
35 Performs a search over an array of @var{nmemb} elements pointed to by
36 @var{base} for a member that matches the object pointed to by @var{key}.
37 The size of each member is specified by @var{size}. The array contents
38 should be sorted in ascending order according to the @var{compar}
39 comparison function. This routine should take two arguments pointing to
40 the @var{key} and to an array member, in that order, and should return an
41 integer less than, equal to, or greater than zero if the @var{key} object
42 is respectively less than, matching, or greater than the array member.
43
44 @end deftypefn
45
46 */
47
48 #include "config.h"
49 #include "ansidecl.h"
50 #include <sys/types.h> /* size_t */
51 #include <stdio.h>
52
53 /*
54 * Perform a binary search.
55 *
56 * The code below is a bit sneaky. After a comparison fails, we
57 * divide the work in half by moving either left or right. If lim
58 * is odd, moving left simply involves halving lim: e.g., when lim
59 * is 5 we look at item 2, so we change lim to 2 so that we will
60 * look at items 0 & 1. If lim is even, the same applies. If lim
61 * is odd, moving right again involes halving lim, this time moving
62 * the base up one item past p: e.g., when lim is 5 we change base
63 * to item 3 and make lim 2 so that we will look at items 3 and 4.
64 * If lim is even, however, we have to shrink it by one before
65 * halving: e.g., when lim is 4, we still looked at item 2, so we
66 * have to make lim 3, then halve, obtaining 1, so that we will only
67 * look at item 3.
68 */
69 void *
70 bsearch (register const void *key, const void *base0,
71 size_t nmemb, register size_t size,
72 register int (*compar)(const void *, const void *))
73 {
74 register const char *base = (const char *) base0;
75 register int lim, cmp;
76 register const void *p;
77
78 for (lim = nmemb; lim != 0; lim >>= 1) {
79 p = base + (lim >> 1) * size;
80 cmp = (*compar)(key, p);
81 if (cmp == 0)
82 return (void *)p;
83 if (cmp > 0) { /* key > p: move right */
84 base = (const char *)p + size;
85 lim--;
86 } /* else move left */
87 }
88 return (NULL);
89 }