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/export.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 */
bsearch(const void * key,const void * base,size_t num,size_t size,int (* cmp)(const void * key,const void * elt))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 const char *pivot;
37 int result;
38
39 while (num > 0) {
40 pivot = base + (num >> 1) * size;
41 result = cmp(key, pivot);
42
43 if (result == 0)
44 return (void *)pivot;
45
46 if (result > 0) {
47 base = pivot + size;
48 num--;
49 }
50 num >>= 1;
51 }
52
53 return NULL;
54 }
55 EXPORT_SYMBOL(bsearch);
56
