rational.h (3939B)
1 /* 2 * rational numbers 3 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at> 4 * 5 * This file is part of Libav. 6 * 7 * Libav 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 * Libav 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 Libav; 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 ((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 */