dma: rework config parsing
[dragonfly.git] / contrib / nvi / clib / bsearch.c
blob6b41ab5fcef86229214e9e71a2d0ad26520291d5
1 /*
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
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. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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31 * SUCH DAMAGE.
34 #include "config.h"
36 #if defined(LIBC_SCCS) && !defined(lint)
37 static const char sccsid[] = "@(#)bsearch.c 8.1 (Berkeley) 6/4/93";
38 #endif /* LIBC_SCCS and not lint */
40 #include <stddef.h>
41 #include <stdlib.h>
43 #include "port.h"
46 * Perform a binary search.
48 * The code below is a bit sneaky. After a comparison fails, we
49 * divide the work in half by moving either left or right. If lim
50 * is odd, moving left simply involves halving lim: e.g., when lim
51 * is 5 we look at item 2, so we change lim to 2 so that we will
52 * look at items 0 & 1. If lim is even, the same applies. If lim
53 * is odd, moving right again involes halving lim, this time moving
54 * the base up one item past p: e.g., when lim is 5 we change base
55 * to item 3 and make lim 2 so that we will look at items 3 and 4.
56 * If lim is even, however, we have to shrink it by one before
57 * halving: e.g., when lim is 4, we still looked at item 2, so we
58 * have to make lim 3, then halve, obtaining 1, so that we will only
59 * look at item 3.
61 * PUBLIC: #ifndef HAVE_BSEARCH
62 * PUBLIC: void *bsearch __P((const void *, const void *, size_t,
63 * PUBLIC: size_t, int (*)(const void *, const void *)));
64 * PUBLIC: #endif
66 void *
67 bsearch(key, base0, nmemb, size, compar)
68 register const void *key;
69 const void *base0;
70 size_t nmemb;
71 register size_t size;
72 register int (*compar) __P((const void *, const void *));
74 register const char *base = base0;
75 register size_t lim;
76 register int cmp;
77 register const void *p;
79 for (lim = nmemb; lim != 0; lim >>= 1) {
80 p = base + (lim >> 1) * size;
81 cmp = (*compar)(key, p);
82 if (cmp == 0)
83 return ((void *)p);
84 if (cmp > 0) { /* key > p: move right */
85 base = (char *)p + size;
86 lim--;
87 } /* else move left */
89 return (NULL);