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/*
* rpihddevice - VDR HD output device for Raspberry Pi
* Copyright (C) 2014, 2015, 2016 Thomas Reufer
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <limits.h>
#include <vdr/tools.h>
#include "tools.h"
#include <algorithm>
/*
* ffmpeg's implementation for rational numbers:
* https://github.com/FFmpeg/FFmpeg/blob/master/libavutil/rational.c
*/
cRational::cRational(double d) :
num(0), den(0)
{
int exp;
frexp(d, &exp);
den = 1LL << (29 - std::max(exp - 1, 0));
num = floor(d * den + 0.5);
Reduce(INT_MAX);
}
bool cRational::Reduce(int max)
{
cRational a0 = cRational(0, 1), a1 = cRational(1, 0);
int sign = (num < 0) ^ (den < 0);
if (int div = Gcd(abs(num), abs(den)))
{
num = abs(num) / div;
den = abs(den) / div;
}
if (num <= max && den <= max)
{
a1 = cRational(num, den);
den = 0;
}
while (den)
{
int x = num / den;
int nextDen = num - den * x;
cRational a2 = cRational(x * a1.num + a0.num, x * a1.den + a0.den);
if (a2.num > max || a2.den > max)
{
if (a1.num)
x = (max - a0.num) / a1.num;
if (a1.den)
x = std::min(x, (max - a0.den) / a1.den);
if (den * (2 * x * a1.den + a0.den) > num * a1.den)
a1 = cRational(x * a1.num + a0.num, x * a1.den + a0.den);
break;
}
a0 = a1;
a1 = a2;
num = den;
den = nextDen;
}
num = sign ? -a1.num : a1.num;
den = a1.den;
return den == 0;
}
/*
* Stein's binary GCD algorithm:
* https://en.wikipedia.org/wiki/Binary_GCD_algorithm
*/
int cRational::Gcd(int u, int v)
{
if (u == v || v == 0)
return u;
if (u == 0)
return v;
// look for factors of 2
if (~u & 1) // u is even
{
if (v & 1) // v is odd
return Gcd(u >> 1, v);
else // both u and v are even
return Gcd(u >> 1, v >> 1) << 1;
}
if (~v & 1) // u is odd, v is even
return Gcd(u, v >> 1);
// reduce larger argument
if (u > v)
return Gcd((u - v) >> 1, v);
return Gcd((v - u) >> 1, u);
}
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