LXR linux/drivers/media/dvb-core/dvb

   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 * intlog2 - computes log2 of a value; the result is shifted left by 24 bits
  29 *
  30 * @value: The value (must be != 0)
  31 *
  32 * to use rational values you can use the following method:
  33 *
  34 *   intlog2(value) = intlog2(value * 2^x) - x * 2^24
  35 *
  36 * Some usecase examples:
  37 *
  38 *      intlog2(8) will give 3 << 24 = 3 * 2^24
  39 *
  40 *      intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
  41 *
  42 *      intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
  43 *
  44 *
  45 * return: log2(value) * 2^24
  46 */
  47extern unsigned int intlog2(u32 value);
  48
  49/**
  50 * intlog10 - computes log10 of a value; the result is shifted left by 24 bits
  51 *
  52 * @value: The value (must be != 0)
  53 *
  54 * to use rational values you can use the following method:
  55 *
  56 *   intlog10(value) = intlog10(value * 10^x) - x * 2^24
  57 *
  58 * An usecase example:
  59 *
  60 *      intlog10(1000) will give 3 << 24 = 3 * 2^24
  61 *
  62 *   due to the implementation intlog10(1000) might be not exactly 3 * 2^24
  63 *
  64 * look at intlog2 for similar examples
  65 *
  66 * return: log10(value) * 2^24
  67 */
  68extern unsigned int intlog10(u32 value);
  69
  70#endif
  71