Fix compile with --disable-muxers, patch by Loïc Le Loarer, lll+ffmpeg m4x org.
[libav.git] / libavutil / rational.c
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1/*
2 * Rational numbers
3 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
4 *
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5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
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8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
b78e7197 10 * version 2.1 of the License, or (at your option) any later version.
5ff85f1d 11 *
b78e7197 12 * FFmpeg is distributed in the hope that it will be useful,
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13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
b78e7197 18 * License along with FFmpeg; if not, write to the Free Software
5509bffa 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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20 *
21 */
115329f1 22
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23/**
24 * @file rational.c
25 * Rational numbers
26 * @author Michael Niedermayer <michaelni@gmx.at>
27 */
28
29//#include <math.h>
30#include <limits.h>
115329f1 31
5ff85f1d 32#include "common.h"
c11c2bc2 33#include "mathematics.h"
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34#include "rational.h"
35
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36int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max){
37 AVRational a0={0,1}, a1={1,0};
38 int sign= (nom<0) ^ (den<0);
c26abfa5 39 int64_t gcd= ff_gcd(FFABS(nom), FFABS(den));
c11c2bc2 40
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41 nom = FFABS(nom)/gcd;
42 den = FFABS(den)/gcd;
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43 if(nom<=max && den<=max){
44 a1= (AVRational){nom, den};
45 den=0;
46 }
115329f1 47
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48 while(den){
49 int64_t x = nom / den;
50 int64_t next_den= nom - den*x;
51 int64_t a2n= x*a1.num + a0.num;
52 int64_t a2d= x*a1.den + a0.den;
53
54 if(a2n > max || a2d > max) break;
55
56 a0= a1;
57 a1= (AVRational){a2n, a2d};
58 nom= den;
59 den= next_den;
60 }
61 assert(ff_gcd(a1.num, a1.den) == 1);
115329f1 62
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63 *dst_nom = sign ? -a1.num : a1.num;
64 *dst_den = a1.den;
115329f1 65
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66 return den==0;
67}
68
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69/**
70 * returns b*c.
71 */
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72AVRational av_mul_q(AVRational b, AVRational c){
73 av_reduce(&b.num, &b.den, b.num * (int64_t)c.num, b.den * (int64_t)c.den, INT_MAX);
74 return b;
75}
76
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77/**
78 * returns b/c.
79 */
5ff85f1d 80AVRational av_div_q(AVRational b, AVRational c){
79dc59b7 81 return av_mul_q(b, (AVRational){c.den, c.num});
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82}
83
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84/**
85 * returns b+c.
86 */
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87AVRational av_add_q(AVRational b, AVRational c){
88 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);
89 return b;
90}
91
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92/**
93 * returns b-c.
94 */
5ff85f1d 95AVRational av_sub_q(AVRational b, AVRational c){
79dc59b7 96 return av_add_q(b, (AVRational){-c.num, c.den});
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97}
98
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99/**
100 * Converts a double precission floating point number to a AVRational.
101 * @param max the maximum allowed numerator and denominator
102 */
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103AVRational av_d2q(double d, int max){
104 AVRational a;
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105#define LOG2 0.69314718055994530941723212145817656807550013436025
106 int exponent= FFMAX( (int)(log(fabs(d) + 1e-20)/LOG2), 0);
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107 int64_t den= 1LL << (61 - exponent);
108 av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max);
109
110 return a;
111}