1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <stddef.h>
33 #include <stdlib.h>
34
35 #ifdef I_AM_BSEARCH_S
36 #include <errno.h>
37 #include <stdint.h>
38 #include "libc_private.h"
39 #endif
40
41 #ifdef I_AM_BSEARCH_B
42 #include "block_abi.h"
43 #define COMPAR(x,y) CALL_BLOCK(compar, x, y)
44 typedef DECLARE_BLOCK(int, compar_block, const void *, const void *);
45 #elif defined(I_AM_BSEARCH_S)
46 #define COMPAR(x,y) compar((x), (y), context)
47 #else
48 #define COMPAR(x,y) compar(x, y)
49 #endif
50
51 /*
52 * Perform a binary search.
53 *
54 * The code below is a bit sneaky. After a comparison fails, we
55 * divide the work in half by moving either left or right. If lim
56 * is odd, moving left simply involves halving lim: e.g., when lim
57 * is 5 we look at item 2, so we change lim to 2 so that we will
58 * look at items 0 & 1. If lim is even, the same applies. If lim
59 * is odd, moving right again involves halving lim, this time moving
60 * the base up one item past p: e.g., when lim is 5 we change base
61 * to item 3 and make lim 2 so that we will look at items 3 and 4.
62 * If lim is even, however, we have to shrink it by one before
63 * halving: e.g., when lim is 4, we still looked at item 2, so we
64 * have to make lim 3, then halve, obtaining 1, so that we will only
65 * look at item 3.
66 */
67 #ifdef I_AM_BSEARCH_B
68 void *
bsearch_b(const void * key,const void * base0,size_t nmemb,size_t size,compar_block compar)69 bsearch_b(const void *key, const void *base0, size_t nmemb, size_t size,
70 compar_block compar)
71 #elif defined(I_AM_BSEARCH_S)
72 void *
73 bsearch_s(const void *key, const void *base0, rsize_t nmemb, rsize_t size,
74 int (*compar)(const void *, const void *, void *), void *context)
75 #else
76 void *
77 bsearch(const void *key, const void *base0, size_t nmemb, size_t size,
78 int (*compar)(const void *, const void *))
79 #endif
80 {
81 const char *base = base0;
82 size_t lim;
83 int cmp;
84 const void *p;
85
86 #ifdef I_AM_BSEARCH_S
87 if (nmemb > RSIZE_MAX) {
88 __throw_constraint_handler_s("bsearch_s : nmemb > RSIZE_MAX",
89 EINVAL);
90 return (NULL);
91 } else if (size > RSIZE_MAX) {
92 __throw_constraint_handler_s("bsearch_s : size > RSIZE_MAX",
93 EINVAL);
94 return (NULL);
95 } else if (nmemb != 0) {
96 if (key == NULL) {
97 __throw_constraint_handler_s("bsearch_s : key == NULL",
98 EINVAL);
99 return (NULL);
100 } else if (base0 == NULL) {
101 __throw_constraint_handler_s("bsearch_s : base == NULL",
102 EINVAL);
103 return (NULL);
104 } else if (compar == NULL) {
105 __throw_constraint_handler_s("bsearch_s : compar == NULL",
106 EINVAL);
107 return (NULL);
108 }
109 }
110 #endif
111
112 for (lim = nmemb; lim != 0; lim >>= 1) {
113 p = base + (lim >> 1) * size;
114 cmp = COMPAR(key, p);
115 if (cmp == 0)
116 return ((void *)p);
117 if (cmp > 0) { /* key > p: move right */
118 base = (char *)p + size;
119 lim--;
120 } /* else move left */
121 }
122 return (NULL);
123 }
124