Christoph Pfister | da22d0e | 2006-05-22 10:32:04 -0300 | [diff] [blame] | 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 | * You should have received a copy of the GNU Lesser General Public |
| 18 | * License along with this library; if not, write to the Free Software |
| 19 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 20 | */ |
| 21 | |
| 22 | #ifndef __DVB_MATH_H |
| 23 | #define __DVB_MATH_H |
| 24 | |
| 25 | #include <linux/types.h> |
| 26 | |
| 27 | /** |
| 28 | * computes log2 of a value; the result is shifted left by 24 bits |
| 29 | * |
| 30 | * to use rational values you can use the following method: |
| 31 | * intlog2(value) = intlog2(value * 2^x) - x * 2^24 |
| 32 | * |
| 33 | * example: intlog2(8) will give 3 << 24 = 3 * 2^24 |
| 34 | * example: intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24 |
| 35 | * example: intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24 |
| 36 | * |
| 37 | * @param value The value (must be != 0) |
| 38 | * @return log2(value) * 2^24 |
| 39 | */ |
| 40 | extern unsigned int intlog2(u32 value); |
| 41 | |
| 42 | /** |
| 43 | * computes log10 of a value; the result is shifted left by 24 bits |
| 44 | * |
| 45 | * to use rational values you can use the following method: |
| 46 | * intlog10(value) = intlog10(value * 10^x) - x * 2^24 |
| 47 | * |
| 48 | * example: intlog10(1000) will give 3 << 24 = 3 * 2^24 |
| 49 | * due to the implementation intlog10(1000) might be not exactly 3 * 2^24 |
| 50 | * |
| 51 | * look at intlog2 for similar examples |
| 52 | * |
| 53 | * @param value The value (must be != 0) |
| 54 | * @return log10(value) * 2^24 |
| 55 | */ |
| 56 | extern unsigned int intlog10(u32 value); |
| 57 | |
| 58 | #endif |