Root/lib/bsearch.c

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 */
33void *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}
53EXPORT_SYMBOL(bsearch);
54

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