rational.h 3.85 KB
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/*
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 * rational numbers
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 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav is distributed in the hope that it will be useful,
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 * 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
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file
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 * rational numbers
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 * @author Michael Niedermayer <michaelni@gmx.at>
 */

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#ifndef AVUTIL_RATIONAL_H
#define AVUTIL_RATIONAL_H
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#include <stdint.h>
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#include <limits.h>
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#include "attributes.h"
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/**
 * @addtogroup lavu_math
 * @{
 */

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

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/**
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 * Compare two rationals.
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 * @param a first rational
 * @param b second rational
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 * @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
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 */
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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;

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    if(tmp) return ((tmp ^ a.den ^ b.den)>>63)|1;
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    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;
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}

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

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/**
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 * Reduce a fraction.
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 * This is useful for framerate calculations.
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 * @param dst_num destination numerator
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 * @param dst_den destination denominator
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 * @param num source numerator
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 * @param den source denominator
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 * @param max the maximum allowed for dst_num & dst_den
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 * @return 1 if exact, 0 otherwise
 */
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int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max);
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/**
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 * Multiply two rationals.
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 * @param b first rational
 * @param c second rational
 * @return b*c
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 */
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AVRational av_mul_q(AVRational b, AVRational c) av_const;
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/**
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 * Divide one rational by another.
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 * @param b first rational
 * @param c second rational
 * @return b/c
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 */
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AVRational av_div_q(AVRational b, AVRational c) av_const;
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/**
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 * Add two rationals.
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 * @param b first rational
 * @param c second rational
 * @return b+c
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 */
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AVRational av_add_q(AVRational b, AVRational c) av_const;
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/**
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 * Subtract one rational from another.
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 * @param b first rational
 * @param c second rational
 * @return b-c
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 */
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AVRational av_sub_q(AVRational b, AVRational c) av_const;
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/**
 * 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;
}

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/**
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 * Convert a double precision floating point number to a rational.
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 * inf is expressed as {1,0} or {-1,0} depending on the sign.
 *
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 * @param d double to convert
 * @param max the maximum allowed numerator and denominator
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 * @return (AVRational) d
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 */
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AVRational av_d2q(double d, int max) av_const;
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/**
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 * @return 1 if q1 is nearer to q than q2, -1 if q2 is nearer
 * than q1, 0 if they have the same distance.
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 */
int av_nearer_q(AVRational q, AVRational q1, AVRational q2);

/**
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 * Find the nearest value in q_list to q.
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 * @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);

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/**
 * @}
 */

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#endif /* AVUTIL_RATIONAL_H */