rational.h (4364B)
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 */