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 <xen/lib.h>
13
14 /*
15 * bsearch - binary search an array of elements
16 * @key: pointer to item being searched for
17 * @base: pointer to first element to search
18 * @num: number of elements
19 * @size: size of each element
20 * @cmp: pointer to comparison function
21 *
22 * This function does a binary search on the given array. The
23 * contents of the array should already be in ascending sorted order
24 * under the provided comparison function.
25 *
26 * Note that the key need not have the same type as the elements in
27 * the array, e.g. key could be a string and the comparison function
28 * could compare the string with the struct's name field. However, if
29 * the key and elements in the array are of the same type, you can use
30 * the same comparison function for both sort() and bsearch().
31 */
bsearch(const void * key,const void * base,size_t num,size_t size,int (* cmp)(const void * key,const void * elt))32 void *bsearch(const void *key, const void *base, size_t num, size_t size,
33 int (*cmp)(const void *key, const void *elt))
34 {
35 size_t start = 0, end = num;
36 int result;
37
38 while (start < end) {
39 size_t mid = start + (end - start) / 2;
40
41 result = cmp(key, base + mid * size);
42 if (result < 0)
43 end = mid;
44 else if (result > 0)
45 start = mid + 1;
46 else
47 return (void *)base + mid * size;
48 }
49
50 return NULL;
51 }
52