mirror of https://git.ffmpeg.org/ffmpeg.git
111 lines
2.9 KiB
C
111 lines
2.9 KiB
C
/*
|
|
* Rational numbers
|
|
* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
|
|
*
|
|
* 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 of the License, or (at your option) any later version.
|
|
*
|
|
* This library 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.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with this library; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*
|
|
*/
|
|
|
|
/**
|
|
* @file rational.c
|
|
* Rational numbers
|
|
* @author Michael Niedermayer <michaelni@gmx.at>
|
|
*/
|
|
|
|
//#include <math.h>
|
|
#include <limits.h>
|
|
|
|
#include "common.h"
|
|
#include "mathematics.h"
|
|
#include "rational.h"
|
|
|
|
int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max){
|
|
AVRational a0={0,1}, a1={1,0};
|
|
int sign= (nom<0) ^ (den<0);
|
|
int64_t gcd= ff_gcd(ABS(nom), ABS(den));
|
|
|
|
nom = ABS(nom)/gcd;
|
|
den = ABS(den)/gcd;
|
|
if(nom<=max && den<=max){
|
|
a1= (AVRational){nom, den};
|
|
den=0;
|
|
}
|
|
|
|
while(den){
|
|
int64_t x = nom / den;
|
|
int64_t next_den= nom - den*x;
|
|
int64_t a2n= x*a1.num + a0.num;
|
|
int64_t a2d= x*a1.den + a0.den;
|
|
|
|
if(a2n > max || a2d > max) break;
|
|
|
|
a0= a1;
|
|
a1= (AVRational){a2n, a2d};
|
|
nom= den;
|
|
den= next_den;
|
|
}
|
|
assert(ff_gcd(a1.num, a1.den) == 1);
|
|
|
|
*dst_nom = sign ? -a1.num : a1.num;
|
|
*dst_den = a1.den;
|
|
|
|
return den==0;
|
|
}
|
|
|
|
/**
|
|
* returns b*c.
|
|
*/
|
|
AVRational av_mul_q(AVRational b, AVRational c){
|
|
av_reduce(&b.num, &b.den, b.num * (int64_t)c.num, b.den * (int64_t)c.den, INT_MAX);
|
|
return b;
|
|
}
|
|
|
|
/**
|
|
* returns b/c.
|
|
*/
|
|
AVRational av_div_q(AVRational b, AVRational c){
|
|
av_reduce(&b.num, &b.den, b.num * (int64_t)c.den, b.den * (int64_t)c.num, INT_MAX);
|
|
return b;
|
|
}
|
|
|
|
/**
|
|
* returns b+c.
|
|
*/
|
|
AVRational av_add_q(AVRational b, AVRational c){
|
|
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);
|
|
return b;
|
|
}
|
|
|
|
/**
|
|
* returns b-c.
|
|
*/
|
|
AVRational av_sub_q(AVRational b, AVRational c){
|
|
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);
|
|
return b;
|
|
}
|
|
|
|
/**
|
|
* Converts a double precission floating point number to a AVRational.
|
|
* @param max the maximum allowed numerator and denominator
|
|
*/
|
|
AVRational av_d2q(double d, int max){
|
|
AVRational a;
|
|
int exponent= FFMAX( (int)(log(ABS(d) + 1e-20)/log(2)), 0);
|
|
int64_t den= 1LL << (61 - exponent);
|
|
av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max);
|
|
|
|
return a;
|
|
}
|