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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 | |
12 | #include <linux/module.h> |
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 | { |
36 | size_t start = 0, end = num; |
37 | int result; |
38 | |
39 | while (start < end) { |
40 | size_t mid = start + (end - start) / 2; |
41 | |
42 | result = cmp(key, base + mid * size); |
43 | if (result < 0) |
44 | end = mid; |
45 | else if (result > 0) |
46 | start = mid + 1; |
47 | else |
48 | return (void *)base + mid * size; |
49 | } |
50 | |
51 | return NULL; |
52 | } |
53 | EXPORT_SYMBOL(bsearch); |
54 |
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