/src/binutils-gdb/libiberty/bsearch_r.c
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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 [rescinded 22 July 1999] |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_r (const void *@var{key}, @ |
34 | | const void *@var{base}, size_t @var{nmemb}, size_t @var{size}, @ |
35 | | int (*@var{compar})(const void *, const void *, void *), void *@var{arg}) |
36 | | |
37 | | Performs a search over an array of @var{nmemb} elements pointed to by |
38 | | @var{base} for a member that matches the object pointed to by @var{key}. |
39 | | The size of each member is specified by @var{size}. The array contents |
40 | | should be sorted in ascending order according to the @var{compar} |
41 | | comparison function. This routine should take three arguments: the first |
42 | | two point to the @var{key} and to an array member, and the last is passed |
43 | | down unchanged from @code{bsearch_r}'s last argument. It should return an |
44 | | integer less than, equal to, or greater than zero if the @var{key} object |
45 | | is respectively less than, matching, or greater than the array member. |
46 | | |
47 | | @end deftypefn |
48 | | |
49 | | */ |
50 | | |
51 | | #include "config.h" |
52 | | #include "ansidecl.h" |
53 | | #include <sys/types.h> /* size_t */ |
54 | | #include <stdio.h> |
55 | | |
56 | | /* |
57 | | * Perform a binary search. |
58 | | * |
59 | | * The code below is a bit sneaky. After a comparison fails, we |
60 | | * divide the work in half by moving either left or right. If lim |
61 | | * is odd, moving left simply involves halving lim: e.g., when lim |
62 | | * is 5 we look at item 2, so we change lim to 2 so that we will |
63 | | * look at items 0 & 1. If lim is even, the same applies. If lim |
64 | | * is odd, moving right again involes halving lim, this time moving |
65 | | * the base up one item past p: e.g., when lim is 5 we change base |
66 | | * to item 3 and make lim 2 so that we will look at items 3 and 4. |
67 | | * If lim is even, however, we have to shrink it by one before |
68 | | * halving: e.g., when lim is 4, we still looked at item 2, so we |
69 | | * have to make lim 3, then halve, obtaining 1, so that we will only |
70 | | * look at item 3. |
71 | | */ |
72 | | void * |
73 | | bsearch_r (const void *key, const void *base0, |
74 | | size_t nmemb, size_t size, |
75 | | int (*compar)(const void *, const void *, void *), |
76 | | void *arg) |
77 | 0 | { |
78 | 0 | const char *base = (const char *) base0; |
79 | 0 | int lim, cmp; |
80 | 0 | const void *p; |
81 | |
|
82 | 0 | for (lim = nmemb; lim != 0; lim >>= 1) { |
83 | 0 | p = base + (lim >> 1) * size; |
84 | 0 | cmp = (*compar)(key, p, arg); |
85 | 0 | if (cmp == 0) |
86 | 0 | return (void *)p; |
87 | 0 | if (cmp > 0) { /* key > p: move right */ |
88 | 0 | base = (const char *)p + size; |
89 | 0 | lim--; |
90 | 0 | } /* else move left */ |
91 | 0 | } |
92 | 0 | return (NULL); |
93 | 0 | } |