1/*
 2 * dvb-math provides some complex fixed-point math
 3 * operations shared between the dvb related stuff
 4 *
 5 * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
 6 *
 7 * This library is free software; you can redistribute it and/or modify
 8 * it under the terms of the GNU Lesser General Public License as
 9 * published by the Free Software Foundation; either version 2.1 of
10 * the License, or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU Lesser General Public License for more details.
16 */
17
18#ifndef __DVB_MATH_H
19#define __DVB_MATH_H
20
21#include <linux/types.h>
22
23/**
24 * intlog2 - computes log2 of a value; the result is shifted left by 24 bits
25 *
26 * @value: The value (must be != 0)
27 *
28 * to use rational values you can use the following method:
29 *
30 *   intlog2(value) = intlog2(value * 2^x) - x * 2^24
31 *
32 * Some usecase examples:
33 *
34 *	intlog2(8) will give 3 << 24 = 3 * 2^24
35 *
36 *	intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
37 *
38 *	intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
39 *
40 *
41 * return: log2(value) * 2^24
42 */
43extern unsigned int intlog2(u32 value);
44
45/**
46 * intlog10 - computes log10 of a value; the result is shifted left by 24 bits
47 *
48 * @value: The value (must be != 0)
49 *
50 * to use rational values you can use the following method:
51 *
52 *   intlog10(value) = intlog10(value * 10^x) - x * 2^24
53 *
54 * An usecase example:
55 *
56 *	intlog10(1000) will give 3 << 24 = 3 * 2^24
57 *
58 *   due to the implementation intlog10(1000) might be not exactly 3 * 2^24
59 *
60 * look at intlog2 for similar examples
61 *
62 * return: log10(value) * 2^24
63 */
64extern unsigned int intlog10(u32 value);
65
66#endif