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rational.h
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1 /*
2  * rational numbers
3  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
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
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * @file
24  * rational numbers
25  * @author Michael Niedermayer <michaelni@gmx.at>
26  */
27 
28 #ifndef AVUTIL_RATIONAL_H
29 #define AVUTIL_RATIONAL_H
30 
31 #include <stdint.h>
32 #include <limits.h>
33 #include "attributes.h"
34 
35 /**
36  * @addtogroup lavu_math
37  * @{
38  */
39 
40 /**
41  * rational number numerator/denominator
42  */
43 typedef struct AVRational{
44  int num; ///< numerator
45  int den; ///< denominator
46 } AVRational;
47 
48 /**
49  * Compare two rationals.
50  * @param a first rational
51  * @param b second rational
52  * @return 0 if a==b, 1 if a>b, -1 if a<b, and INT_MIN if one of the
53  * values is of the form 0/0
54  */
55 static inline int av_cmp_q(AVRational a, AVRational b){
56  const int64_t tmp= a.num * (int64_t)b.den - b.num * (int64_t)a.den;
57 
58  if(tmp) return (int)((tmp ^ a.den ^ b.den)>>63)|1;
59  else if(b.den && a.den) return 0;
60  else if(a.num && b.num) return (a.num>>31) - (b.num>>31);
61  else return INT_MIN;
62 }
63 
64 /**
65  * Convert rational to double.
66  * @param a rational to convert
67  * @return (double) a
68  */
69 static inline double av_q2d(AVRational a){
70  return a.num / (double) a.den;
71 }
72 
73 /**
74  * Reduce a fraction.
75  * This is useful for framerate calculations.
76  * @param dst_num destination numerator
77  * @param dst_den destination denominator
78  * @param num source numerator
79  * @param den source denominator
80  * @param max the maximum allowed for dst_num & dst_den
81  * @return 1 if exact, 0 otherwise
82  */
83 int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max);
84 
85 /**
86  * Multiply two rationals.
87  * @param b first rational
88  * @param c second rational
89  * @return b*c
90  */
92 
93 /**
94  * Divide one rational by another.
95  * @param b first rational
96  * @param c second rational
97  * @return b/c
98  */
100 
101 /**
102  * Add two rationals.
103  * @param b first rational
104  * @param c second rational
105  * @return b+c
106  */
108 
109 /**
110  * Subtract one rational from another.
111  * @param b first rational
112  * @param c second rational
113  * @return b-c
114  */
116 
117 /**
118  * Invert a rational.
119  * @param q value
120  * @return 1 / q
121  */
123 {
124  AVRational r = { q.den, q.num };
125  return r;
126 }
127 
128 /**
129  * Convert a double precision floating point number to a rational.
130  * inf is expressed as {1,0} or {-1,0} depending on the sign.
131  *
132  * @param d double to convert
133  * @param max the maximum allowed numerator and denominator
134  * @return (AVRational) d
135  */
136 AVRational av_d2q(double d, int max) av_const;
137 
138 /**
139  * @return 1 if q1 is nearer to q than q2, -1 if q2 is nearer
140  * than q1, 0 if they have the same distance.
141  */
143 
144 /**
145  * Find the nearest value in q_list to q.
146  * @param q_list an array of rationals terminated by {0, 0}
147  * @return the index of the nearest value found in the array
148  */
149 int av_find_nearest_q_idx(AVRational q, const AVRational* q_list);
150 
151 /**
152  * @}
153  */
154 
155 #endif /* AVUTIL_RATIONAL_H */