linux-mm / kernel / git / torvalds / linux / 265c5596da61a5467b6b3bfbd9ba637f867d3927 / . / include / media / dvb_math.h

/* | |

* dvb-math provides some complex fixed-point math | |

* operations shared between the dvb related stuff | |

* | |

* Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com) | |

* | |

* This library is free software; you can redistribute it and/or modify | |

* it under the terms of the GNU Lesser General Public License as | |

* published by the Free Software Foundation; either version 2.1 of | |

* the License, or (at your option) any later version. | |

* | |

* This program is distributed in the hope that it will be useful, | |

* but WITHOUT ANY WARRANTY; without even the implied warranty of | |

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |

* GNU Lesser General Public License for more details. | |

*/ | |

#ifndef __DVB_MATH_H | |

#define __DVB_MATH_H | |

#include <linux/types.h> | |

/** | |

* intlog2 - computes log2 of a value; the result is shifted left by 24 bits | |

* | |

* @value: The value (must be != 0) | |

* | |

* to use rational values you can use the following method: | |

* | |

* intlog2(value) = intlog2(value * 2^x) - x * 2^24 | |

* | |

* Some usecase examples: | |

* | |

* intlog2(8) will give 3 << 24 = 3 * 2^24 | |

* | |

* intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24 | |

* | |

* intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24 | |

* | |

* | |

* return: log2(value) * 2^24 | |

*/ | |

extern unsigned int intlog2(u32 value); | |

/** | |

* intlog10 - computes log10 of a value; the result is shifted left by 24 bits | |

* | |

* @value: The value (must be != 0) | |

* | |

* to use rational values you can use the following method: | |

* | |

* intlog10(value) = intlog10(value * 10^x) - x * 2^24 | |

* | |

* An usecase example: | |

* | |

* intlog10(1000) will give 3 << 24 = 3 * 2^24 | |

* | |

* due to the implementation intlog10(1000) might be not exactly 3 * 2^24 | |

* | |

* look at intlog2 for similar examples | |

* | |

* return: log10(value) * 2^24 | |

*/ | |

extern unsigned int intlog10(u32 value); | |

#endif |