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1a94dc35 TA |
1 | /* |
2 | * A generic implementation of binary search for the Linux kernel | |
3 | * | |
4 | * Copyright (C) 2008-2009 Ksplice, Inc. | |
5 | * Author: Tim Abbott <tabbott@ksplice.com> | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or | |
8 | * modify it under the terms of the GNU General Public License as | |
9 | * published by the Free Software Foundation; version 2. | |
10 | */ | |
11 | ||
8bc3bcc9 | 12 | #include <linux/export.h> |
1a94dc35 TA |
13 | #include <linux/bsearch.h> |
14 | ||
15 | /* | |
16 | * bsearch - binary search an array of elements | |
17 | * @key: pointer to item being searched for | |
18 | * @base: pointer to first element to search | |
19 | * @num: number of elements | |
20 | * @size: size of each element | |
21 | * @cmp: pointer to comparison function | |
22 | * | |
23 | * This function does a binary search on the given array. The | |
24 | * contents of the array should already be in ascending sorted order | |
25 | * under the provided comparison function. | |
26 | * | |
27 | * Note that the key need not have the same type as the elements in | |
28 | * the array, e.g. key could be a string and the comparison function | |
29 | * could compare the string with the struct's name field. However, if | |
30 | * the key and elements in the array are of the same type, you can use | |
31 | * the same comparison function for both sort() and bsearch(). | |
32 | */ | |
33 | void *bsearch(const void *key, const void *base, size_t num, size_t size, | |
34 | int (*cmp)(const void *key, const void *elt)) | |
35 | { | |
166a0f78 | 36 | const char *pivot; |
1a94dc35 TA |
37 | int result; |
38 | ||
166a0f78 SS |
39 | while (num > 0) { |
40 | pivot = base + (num >> 1) * size; | |
41 | result = cmp(key, pivot); | |
1a94dc35 | 42 | |
166a0f78 SS |
43 | if (result == 0) |
44 | return (void *)pivot; | |
45 | ||
46 | if (result > 0) { | |
47 | base = pivot + size; | |
48 | num--; | |
49 | } | |
50 | num >>= 1; | |
1a94dc35 TA |
51 | } |
52 | ||
53 | return NULL; | |
54 | } | |
55 | EXPORT_SYMBOL(bsearch); |