mirror of https://gitee.com/openkylin/linux.git
59 lines
1.9 KiB
C
59 lines
1.9 KiB
C
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/*
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* dvb-math provides some complex fixed-point math
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* operations shared between the dvb related stuff
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*
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* Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
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*
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* This library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef __DVB_MATH_H
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#define __DVB_MATH_H
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#include <linux/types.h>
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/**
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* computes log2 of a value; the result is shifted left by 24 bits
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*
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* to use rational values you can use the following method:
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* intlog2(value) = intlog2(value * 2^x) - x * 2^24
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*
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* example: intlog2(8) will give 3 << 24 = 3 * 2^24
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* example: intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
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* example: intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
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*
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* @param value The value (must be != 0)
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* @return log2(value) * 2^24
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*/
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extern unsigned int intlog2(u32 value);
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/**
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* computes log10 of a value; the result is shifted left by 24 bits
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*
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* to use rational values you can use the following method:
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* intlog10(value) = intlog10(value * 10^x) - x * 2^24
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*
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* example: intlog10(1000) will give 3 << 24 = 3 * 2^24
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* due to the implementation intlog10(1000) might be not exactly 3 * 2^24
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*
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* look at intlog2 for similar examples
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*
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* @param value The value (must be != 0)
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* @return log10(value) * 2^24
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*/
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extern unsigned int intlog10(u32 value);
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#endif
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