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111 lines
2.9 KiB
C
111 lines
2.9 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 library 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 of the License, or (at your option) any later version.
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*
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* This library 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 this library; 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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/**
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* @file 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 <math.h>
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#include <limits.h>
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#include "common.h"
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#include "mathematics.h"
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#include "rational.h"
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int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max){
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AVRational a0={0,1}, a1={1,0};
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int sign= (nom<0) ^ (den<0);
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int64_t gcd= ff_gcd(ABS(nom), ABS(den));
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nom = ABS(nom)/gcd;
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den = ABS(den)/gcd;
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if(nom<=max && den<=max){
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a1= (AVRational){nom, den};
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den=0;
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}
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while(den){
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int64_t x = nom / den;
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int64_t next_den= nom - 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) break;
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a0= a1;
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a1= (AVRational){a2n, a2d};
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nom= den;
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den= next_den;
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}
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assert(ff_gcd(a1.num, a1.den) == 1);
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*dst_nom = 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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/**
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* returns b*c.
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*/
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AVRational av_mul_q(AVRational b, AVRational c){
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av_reduce(&b.num, &b.den, b.num * (int64_t)c.num, b.den * (int64_t)c.den, INT_MAX);
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return b;
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}
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/**
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* returns b/c.
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*/
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AVRational av_div_q(AVRational b, AVRational c){
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av_reduce(&b.num, &b.den, b.num * (int64_t)c.den, b.den * (int64_t)c.num, INT_MAX);
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return b;
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}
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/**
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* returns b+c.
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*/
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AVRational av_add_q(AVRational b, AVRational c){
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av_reduce(&b.num, &b.den, b.num * (int64_t)c.den + c.num * (int64_t)b.den, b.den * (int64_t)c.den, INT_MAX);
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return b;
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}
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/**
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* returns b-c.
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*/
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AVRational av_sub_q(AVRational b, AVRational c){
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av_reduce(&b.num, &b.den, b.num * (int64_t)c.den - c.num * (int64_t)b.den, b.den * (int64_t)c.den, INT_MAX);
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return b;
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}
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/**
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* Converts a double precission floating point number to a AVRational.
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* @param max the maximum allowed numerator and denominator
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*/
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AVRational av_d2q(double d, int max){
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AVRational a;
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int exponent= FFMAX( (int)(log(ABS(d) + 1e-20)/log(2)), 0);
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int64_t den= 1LL << (61 - exponent);
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av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max);
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return a;
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}
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