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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.  */
  91. AVRational av_mul_q(AVRational b, AVRational c) av_const;
  92.  
  93. /**
  94.  * Divide one rational by another.
  95.  * @param b first rational
  96.  * @param c second rational
  97.  * @return b/c
  98.  */
  99. AVRational av_div_q(AVRational b, AVRational c) av_const;
  100.  
  101. /**
  102.  * Add two rationals.
  103.  * @param b first rational
  104.  * @param c second rational
  105.  * @return b+c
  106.  */
  107. AVRational av_add_q(AVRational b, AVRational c) av_const;
  108.  
  109. /**
  110.  * Subtract one rational from another.
  111.  * @param b first rational
  112.  * @param c second rational
  113.  * @return b-c
  114.  */
  115. AVRational av_sub_q(AVRational b, AVRational c) av_const;
  116.  
  117. /**
  118.  * Invert a rational.
  119.  * @param q value
  120.  * @return 1 / q
  121.  */
  122. static av_always_inline AVRational av_inv_q(AVRational q)
  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.  */
  142. int av_nearer_q(AVRational q, AVRational q1, AVRational q2);
  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 */
  156.