drivers/media/dvb/dvb-core/dvb_math.h

   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