include/media/dvb_math.h

0001 /*
0002  * dvb-math provides some complex fixed-point math
0003  * operations shared between the dvb related stuff
0004  *
0005  * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
0006  *
0007  * This library is free software; you can redistribute it and/or modify
0008  * it under the terms of the GNU Lesser General Public License as
0009  * published by the Free Software Foundation; either version 2.1 of
0010  * the License, or (at your option) any later version.
0011  *
0012  * This program is distributed in the hope that it will be useful,
0013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
0014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
0015  * GNU Lesser General Public License for more details.
0016  */
0017
0018 #ifndef __DVB_MATH_H
0019 #define __DVB_MATH_H
0020
0021 #include <linux/types.h>
0022
0023 /**
0024  * intlog2 - computes log2 of a value; the result is shifted left by 24 bits
0025  *
0026  * @value: The value (must be != 0)
0027  *
0028  * to use rational values you can use the following method:
0029  *
0030  *   intlog2(value) = intlog2(value * 2^x) - x * 2^24
0031  *
0032  * Some usecase examples:
0033  *
0034  *  intlog2(8) will give 3 << 24 = 3 * 2^24
0035  *
0036  *  intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
0037  *
0038  *  intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
0039  *
0040  *
0041  * return: log2(value) * 2^24
0042  */
0043 extern unsigned int intlog2(u32 value);
0044
0045 /**
0046  * intlog10 - computes log10 of a value; the result is shifted left by 24 bits
0047  *
0048  * @value: The value (must be != 0)
0049  *
0050  * to use rational values you can use the following method:
0051  *
0052  *   intlog10(value) = intlog10(value * 10^x) - x * 2^24
0053  *
0054  * An usecase example:
0055  *
0056  *  intlog10(1000) will give 3 << 24 = 3 * 2^24
0057  *
0058  *   due to the implementation intlog10(1000) might be not exactly 3 * 2^24
0059  *
0060  * look at intlog2 for similar examples
0061  *
0062  * return: log10(value) * 2^24
0063  */
0064 extern unsigned int intlog10(u32 value);
0065
0066 #endif