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  */
43 extern 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  */
64 extern unsigned int intlog10(u32 value);
65 
66 #endif
67