rational.h 3.85 KB
Newer Older
wester committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155
/*
 * rational numbers
 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * rational numbers
 * @author Michael Niedermayer <michaelni@gmx.at>
 */

#ifndef AVUTIL_RATIONAL_H
#define AVUTIL_RATIONAL_H

#include <stdint.h>
#include <limits.h>
#include "attributes.h"

/**
 * @addtogroup lavu_math
 * @{
 */

/**
 * rational number numerator/denominator
 */
typedef struct AVRational{
    int num; ///< numerator
    int den; ///< denominator
} AVRational;

/**
 * Compare two rationals.
 * @param a first rational
 * @param b second rational
 * @return 0 if a==b, 1 if a>b, -1 if a<b, and INT_MIN if one of the
 * values is of the form 0/0
 */
static inline int av_cmp_q(AVRational a, AVRational b){
    const int64_t tmp= a.num * (int64_t)b.den - b.num * (int64_t)a.den;

    if(tmp) return ((tmp ^ a.den ^ b.den)>>63)|1;
    else if(b.den && a.den) return 0;
    else if(a.num && b.num) return (a.num>>31) - (b.num>>31);
    else                    return INT_MIN;
}

/**
 * Convert rational to double.
 * @param a rational to convert
 * @return (double) a
 */
static inline double av_q2d(AVRational a){
    return a.num / (double) a.den;
}

/**
 * Reduce a fraction.
 * This is useful for framerate calculations.
 * @param dst_num destination numerator
 * @param dst_den destination denominator
 * @param num source numerator
 * @param den source denominator
 * @param max the maximum allowed for dst_num & dst_den
 * @return 1 if exact, 0 otherwise
 */
int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max);

/**
 * Multiply two rationals.
 * @param b first rational
 * @param c second rational
 * @return b*c
 */
AVRational av_mul_q(AVRational b, AVRational c) av_const;

/**
 * Divide one rational by another.
 * @param b first rational
 * @param c second rational
 * @return b/c
 */
AVRational av_div_q(AVRational b, AVRational c) av_const;

/**
 * Add two rationals.
 * @param b first rational
 * @param c second rational
 * @return b+c
 */
AVRational av_add_q(AVRational b, AVRational c) av_const;

/**
 * Subtract one rational from another.
 * @param b first rational
 * @param c second rational
 * @return b-c
 */
AVRational av_sub_q(AVRational b, AVRational c) av_const;

/**
 * Invert a rational.
 * @param q value
 * @return 1 / q
 */
static av_always_inline AVRational av_inv_q(AVRational q)
{
    AVRational r = { q.den, q.num };
    return r;
}

/**
 * Convert a double precision floating point number to a rational.
 * inf is expressed as {1,0} or {-1,0} depending on the sign.
 *
 * @param d double to convert
 * @param max the maximum allowed numerator and denominator
 * @return (AVRational) d
 */
AVRational av_d2q(double d, int max) av_const;

/**
 * @return 1 if q1 is nearer to q than q2, -1 if q2 is nearer
 * than q1, 0 if they have the same distance.
 */
int av_nearer_q(AVRational q, AVRational q1, AVRational q2);

/**
 * Find the nearest value in q_list to q.
 * @param q_list an array of rationals terminated by {0, 0}
 * @return the index of the nearest value found in the array
 */
int av_find_nearest_q_idx(AVRational q, const AVRational* q_list);

/**
 * @}
 */

#endif /* AVUTIL_RATIONAL_H */