PeerStreamer

/*

 * 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;

}