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da22d0e7 CP |
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. | |
da22d0e7 CP |
16 | */ |
17 | ||
18 | #ifndef __DVB_MATH_H | |
19 | #define __DVB_MATH_H | |
20 | ||
21 | #include <linux/types.h> | |
22 | ||
23 | /** | |
e383ce07 | 24 | * intlog2 - computes log2 of a value; the result is shifted left by 24 bits |
e08bb6f7 MCC |
25 | * |
26 | * @value: The value (must be != 0) | |
da22d0e7 CP |
27 | * |
28 | * to use rational values you can use the following method: | |
5b8700e9 | 29 | * |
da22d0e7 CP |
30 | * intlog2(value) = intlog2(value * 2^x) - x * 2^24 |
31 | * | |
dc2c8bd3 | 32 | * Some usecase examples: |
5b8700e9 | 33 | * |
dc2c8bd3 | 34 | * intlog2(8) will give 3 << 24 = 3 * 2^24 |
5b8700e9 | 35 | * |
dc2c8bd3 | 36 | * intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24 |
5b8700e9 | 37 | * |
dc2c8bd3 | 38 | * intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24 |
da22d0e7 | 39 | * |
e08bb6f7 MCC |
40 | * |
41 | * return: log2(value) * 2^24 | |
da22d0e7 CP |
42 | */ |
43 | extern unsigned int intlog2(u32 value); | |
44 | ||
45 | /** | |
e08bb6f7 MCC |
46 | * intlog10 - computes log10 of a value; the result is shifted left by 24 bits |
47 | * | |
48 | * @value: The value (must be != 0) | |
da22d0e7 CP |
49 | * |
50 | * to use rational values you can use the following method: | |
5b8700e9 | 51 | * |
da22d0e7 CP |
52 | * intlog10(value) = intlog10(value * 10^x) - x * 2^24 |
53 | * | |
dc2c8bd3 | 54 | * An usecase example: |
5b8700e9 | 55 | * |
dc2c8bd3 | 56 | * intlog10(1000) will give 3 << 24 = 3 * 2^24 |
5b8700e9 | 57 | * |
da22d0e7 CP |
58 | * due to the implementation intlog10(1000) might be not exactly 3 * 2^24 |
59 | * | |
60 | * look at intlog2 for similar examples | |
61 | * | |
e08bb6f7 | 62 | * return: log10(value) * 2^24 |
da22d0e7 CP |
63 | */ |
64 | extern unsigned int intlog10(u32 value); | |
65 | ||
66 | #endif |