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 67