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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.  * Create a rational.
  50.  * Useful for compilers that do not support compound literals.
  51.  * @note  The return value is not reduced.
  52.  */
  53. static inline AVRational av_make_q(int num, int den)
  54. {
  55.     AVRational r = { num, den };
  56.     return r;
  57. }
  58.  
  59. /**
  60.  * Compare two rationals.
  61.  * @param a first rational
  62.  * @param b second rational
  63.  * @return 0 if a==b, 1 if a>b, -1 if a<b, and INT_MIN if one of the
  64.  * values is of the form 0/0
  65.  */
  66. static inline int av_cmp_q(AVRational a, AVRational b){
  67.     const int64_t tmp= a.num * (int64_t)b.den - b.num * (int64_t)a.den;
  68.  
  69.     if(tmp) return (int)((tmp ^ a.den ^ b.den)>>63)|1;
  70.     else if(b.den && a.den) return 0;
  71.     else if(a.num && b.num) return (a.num>>31) - (b.num>>31);
  72.     else                    return INT_MIN;
  73. }
  74.  
  75. /**
  76.  * Convert rational to double.
  77.  * @param a rational to convert
  78.  * @return (double) a
  79.  */
  80. static inline double av_q2d(AVRational a){
  81.     return a.num / (double) a.den;
  82. }
  83.  
  84. /**
  85.  * Reduce a fraction.
  86.  * This is useful for framerate calculations.
  87.  * @param dst_num destination numerator
  88.  * @param dst_den destination denominator
  89.  * @param num source numerator
  90.  * @param den source denominator
  91.  * @param max the maximum allowed for dst_num & dst_den
  92.  * @return 1 if exact, 0 otherwise
  93.  */
  94. int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max);
  95.  
  96. /**
  97.  * Multiply two rationals.
  98.  * @param b first rational
  99.  * @param c second rational
  100.  * @return b*c
  101.  */
  102. AVRational av_mul_q(AVRational b, AVRational c) av_const;
  103.  
  104. /**
  105.  * Divide one rational by another.
  106.  * @param b first rational
  107.  * @param c second rational
  108.  * @return b/c
  109.  */
  110. AVRational av_div_q(AVRational b, AVRational c) av_const;
  111.  
  112. /**
  113.  * Add two rationals.
  114.  * @param b first rational
  115.  * @param c second rational
  116.  * @return b+c
  117.  */
  118. AVRational av_add_q(AVRational b, AVRational c) av_const;
  119.  
  120. /**
  121.  * Subtract one rational from another.
  122.  * @param b first rational
  123.  * @param c second rational
  124.  * @return b-c
  125.  */
  126. AVRational av_sub_q(AVRational b, AVRational c) av_const;
  127.  
  128. /**
  129.  * Invert a rational.
  130.  * @param q value
  131.  * @return 1 / q
  132.  */
  133. static av_always_inline AVRational av_inv_q(AVRational q)
  134. {
  135.     AVRational r = { q.den, q.num };
  136.     return r;
  137. }
  138.  
  139. /**
  140.  * Convert a double precision floating point number to a rational.
  141.  * inf is expressed as {1,0} or {-1,0} depending on the sign.
  142.  *
  143.  * @param d double to convert
  144.  * @param max the maximum allowed numerator and denominator
  145.  * @return (AVRational) d
  146.  */
  147. AVRational av_d2q(double d, int max) av_const;
  148.  
  149. /**
  150.  * @return 1 if q1 is nearer to q than q2, -1 if q2 is nearer
  151.  * than q1, 0 if they have the same distance.
  152.  */
  153. int av_nearer_q(AVRational q, AVRational q1, AVRational q2);
  154.  
  155. /**
  156.  * Find the nearest value in q_list to q.
  157.  * @param q_list an array of rationals terminated by {0, 0}
  158.  * @return the index of the nearest value found in the array
  159.  */
  160. int av_find_nearest_q_idx(AVRational q, const AVRational* q_list);
  161.  
  162. /**
  163.  * Converts a AVRational to a IEEE 32bit float.
  164.  *
  165.  * The float is returned in a uint32_t and its value is platform indepenant.
  166.  */
  167. uint32_t av_q2intfloat(AVRational q);
  168.  
  169. /**
  170.  * @}
  171.  */
  172.  
  173. #endif /* AVUTIL_RATIONAL_H */
  174.