84 lines
2.2 KiB
C++
84 lines
2.2 KiB
C++
/*
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* rational numbers
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* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg 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 GNU
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* 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 FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file libavutil/rational.c
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* rational numbers
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* @author Michael Niedermayer <michaelni@gmx.at>
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*/
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#include <assert.h>
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#include <limits.h>
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#include "common.h"
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#include "rational.h"
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int64_t av_gcd(int64_t a, int64_t b){
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if(b) return av_gcd(b, a%b);
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return a;
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}
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int av_reduce(int &dst_num, int &dst_den, int64_t num, int64_t den, int64_t max) {
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AVRational a0={0,1}, a1={1,0};
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int sign= (num<0) ^ (den<0);
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int64_t gcd= av_gcd(FFABS(num), FFABS(den));
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if(gcd){
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num = FFABS(num)/gcd;
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den = FFABS(den)/gcd;
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}
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if(num<=max && den<=max){
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a1.num = num;
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a1.den = den;
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den=0;
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}
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while(den){
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uint64_t x = num / den;
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int64_t next_den= num - den*x;
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int64_t a2n= x*a1.num + a0.num;
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int64_t a2d= x*a1.den + a0.den;
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if(a2n > max || a2d > max){
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if(a1.num) x= (max - a0.num) / a1.num;
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if(a1.den) x= FFMIN(x, (max - a0.den) / a1.den);
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if (den*(2*x*a1.den + a0.den) > num*a1.den) {
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a1.den =x*a1.den + a0.den;
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a1.num =x*a1.num + a0.num;
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}
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break;
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}
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a0 = a1;
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a1.den = a2d;
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a1.num = a2n;
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num = den;
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den = next_den;
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}
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assert(av_gcd(a1.num, a1.den) <= 1U);
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dst_num = sign ? -a1.num : a1.num;
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dst_den = a1.den;
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return den==0;
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}
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