1/* SPDX-License-Identifier: LGPL-2.1-or-later */
2/*
3 * Provides fixed-point logarithm operations.
4 *
5 * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
6 */
7
8#ifndef __LINUX_INT_LOG_H
9#define __LINUX_INT_LOG_H
10
11#include <linux/types.h>
12
13/**
14 * intlog2 - computes log2 of a value; the result is shifted left by 24 bits
15 *
16 * @value: The value (must be != 0)
17 *
18 * to use rational values you can use the following method:
19 *
20 * intlog2(value) = intlog2(value * 2^x) - x * 2^24
21 *
22 * Some usecase examples:
23 *
24 * intlog2(8) will give 3 << 24 = 3 * 2^24
25 *
26 * intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
27 *
28 * intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
29 *
30 *
31 * return: log2(value) * 2^24
32 */
33extern unsigned int intlog2(u32 value);
34
35/**
36 * intlog10 - computes log10 of a value; the result is shifted left by 24 bits
37 *
38 * @value: The value (must be != 0)
39 *
40 * to use rational values you can use the following method:
41 *
42 * intlog10(value) = intlog10(value * 10^x) - x * 2^24
43 *
44 * An usecase example:
45 *
46 * intlog10(1000) will give 3 << 24 = 3 * 2^24
47 *
48 * due to the implementation intlog10(1000) might be not exactly 3 * 2^24
49 *
50 * look at intlog2 for similar examples
51 *
52 * return: log10(value) * 2^24
53 */
54extern unsigned int intlog10(u32 value);
55
56#endif
57