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/*
* Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
* 2000 Wim Taymans <wtay@chello.be>
* 2002 Thomas Vander Stichele <thomas@apestaart.org>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
* Fraction utility functions in this file comes from gstutils.c in gstreamer.
*/
#include "config.h"
#include "core/meta-fraction.h"
#include <glib.h>
#include <math.h>
#define MAX_TERMS 30
#define MIN_DIVISOR 1.0e-10
#define MAX_ERROR 1.0e-20
static int
greatest_common_divisor (int a,
int b)
{
while (b != 0)
{
int temp = a;
a = b;
b = temp % b;
}
return ABS (a);
}
MetaFraction
meta_fraction_from_double (double src)
{
double V, F; /* double being converted */
int N, D; /* will contain the result */
int A; /* current term in continued fraction */
int64_t N1, D1; /* numerator, denominator of last approx */
int64_t N2, D2; /* numerator, denominator of previous approx */
int i;
int gcd;
gboolean negative = FALSE;
/* initialize fraction being converted */
F = src;
if (F < 0.0)
{
F = -F;
negative = TRUE;
}
V = F;
/* initialize fractions with 1/0, 0/1 */
N1 = 1;
D1 = 0;
N2 = 0;
D2 = 1;
N = 1;
D = 1;
for (i = 0; i < MAX_TERMS; i++)
{
/* get next term */
A = (gint) F; /* no floor() needed, F is always >= 0 */
/* get new divisor */
F = F - A;
/* calculate new fraction in temp */
N2 = N1 * A + N2;
D2 = D1 * A + D2;
/* guard against overflow */
if (N2 > G_MAXINT || D2 > G_MAXINT)
break;
N = N2;
D = D2;
/* save last two fractions */
N2 = N1;
D2 = D1;
N1 = N;
D1 = D;
/* quit if dividing by zero or close enough to target */
if (F < MIN_DIVISOR || fabs (V - ((gdouble) N) / D) < MAX_ERROR)
break;
/* Take reciprocal */
F = 1 / F;
}
/* fix for overflow */
if (D == 0)
{
N = G_MAXINT;
D = 1;
}
/* fix for negative */
if (negative)
N = -N;
/* simplify */
gcd = greatest_common_divisor (N, D);
if (gcd)
{
N /= gcd;
D /= gcd;
}
return (MetaFraction) {
.num = N,
.denom = D
};
}
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