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20a30077c3
av_gcd is now always defined regardless of input. This documents this change in the "documented API". Two benefits (closely related): 1. The function is robust, and there is no need to worry about INT64_MIN, etc. 2. Clients of av_gcd, like av_reduce, can now be made fully correct. Currently, av_reduce can trigger undefined behavior if e.g num is INT64_MIN due to integer overflow in the FFABS. Furthermore, this undefined behavior is completely undocumented, and could be a fuzzer's paradise. The FFABS was needed in the past as av_gcd was undefined for negative inputs. In order to make av_reduce robust, it is essential to guarantee that av_gcd works for all int64_t. Reviewed-by: Michael Niedermayer <michael@niedermayer.cc> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
166 lines
5.1 KiB
C
166 lines
5.1 KiB
C
/*
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* copyright (c) 2005-2012 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* 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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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; 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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#ifndef AVUTIL_MATHEMATICS_H
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#define AVUTIL_MATHEMATICS_H
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#include <stdint.h>
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#include <math.h>
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#include "attributes.h"
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#include "rational.h"
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#include "intfloat.h"
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#ifndef M_E
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#define M_E 2.7182818284590452354 /* e */
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#endif
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#ifndef M_LN2
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#define M_LN2 0.69314718055994530942 /* log_e 2 */
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#endif
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#ifndef M_LN10
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#define M_LN10 2.30258509299404568402 /* log_e 10 */
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#endif
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#ifndef M_LOG2_10
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#define M_LOG2_10 3.32192809488736234787 /* log_2 10 */
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#endif
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#ifndef M_PHI
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#define M_PHI 1.61803398874989484820 /* phi / golden ratio */
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#endif
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#ifndef M_PI
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#define M_PI 3.14159265358979323846 /* pi */
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#endif
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#ifndef M_PI_2
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#define M_PI_2 1.57079632679489661923 /* pi/2 */
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#endif
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#ifndef M_SQRT1_2
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#define M_SQRT1_2 0.70710678118654752440 /* 1/sqrt(2) */
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#endif
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#ifndef M_SQRT2
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#define M_SQRT2 1.41421356237309504880 /* sqrt(2) */
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#endif
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#ifndef NAN
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#define NAN av_int2float(0x7fc00000)
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#endif
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#ifndef INFINITY
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#define INFINITY av_int2float(0x7f800000)
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#endif
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/**
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* @addtogroup lavu_math
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* @{
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*/
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enum AVRounding {
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AV_ROUND_ZERO = 0, ///< Round toward zero.
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AV_ROUND_INF = 1, ///< Round away from zero.
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AV_ROUND_DOWN = 2, ///< Round toward -infinity.
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AV_ROUND_UP = 3, ///< Round toward +infinity.
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AV_ROUND_NEAR_INF = 5, ///< Round to nearest and halfway cases away from zero.
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AV_ROUND_PASS_MINMAX = 8192, ///< Flag to pass INT64_MIN/MAX through instead of rescaling, this avoids special cases for AV_NOPTS_VALUE
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};
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/**
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* Compute the greatest common divisor of a and b.
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*
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* @return gcd of a and b up to sign; if a >= 0 and b >= 0, return value is >= 0;
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* if a == 0 and b == 0, returns 0.
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*/
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int64_t av_const av_gcd(int64_t a, int64_t b);
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/**
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* Rescale a 64-bit integer with rounding to nearest.
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* A simple a*b/c isn't possible as it can overflow.
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*/
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int64_t av_rescale(int64_t a, int64_t b, int64_t c) av_const;
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/**
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* Rescale a 64-bit integer with specified rounding.
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* A simple a*b/c isn't possible as it can overflow.
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*
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* @return rescaled value a, or if AV_ROUND_PASS_MINMAX is set and a is
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* INT64_MIN or INT64_MAX then a is passed through unchanged.
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*/
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int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding) av_const;
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/**
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* Rescale a 64-bit integer by 2 rational numbers.
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*/
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int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const;
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/**
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* Rescale a 64-bit integer by 2 rational numbers with specified rounding.
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*
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* @return rescaled value a, or if AV_ROUND_PASS_MINMAX is set and a is
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* INT64_MIN or INT64_MAX then a is passed through unchanged.
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*/
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int64_t av_rescale_q_rnd(int64_t a, AVRational bq, AVRational cq,
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enum AVRounding) av_const;
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/**
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* Compare 2 timestamps each in its own timebases.
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* The result of the function is undefined if one of the timestamps
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* is outside the int64_t range when represented in the others timebase.
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* @return -1 if ts_a is before ts_b, 1 if ts_a is after ts_b or 0 if they represent the same position
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*/
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int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b);
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/**
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* Compare 2 integers modulo mod.
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* That is we compare integers a and b for which only the least
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* significant log2(mod) bits are known.
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*
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* @param mod must be a power of 2
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* @return a negative value if a is smaller than b
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* a positive value if a is greater than b
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* 0 if a equals b
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*/
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int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod);
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/**
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* Rescale a timestamp while preserving known durations.
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*
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* @param in_ts Input timestamp
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* @param in_tb Input timebase
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* @param fs_tb Duration and *last timebase
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* @param duration duration till the next call
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* @param out_tb Output timebase
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*/
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int64_t av_rescale_delta(AVRational in_tb, int64_t in_ts, AVRational fs_tb, int duration, int64_t *last, AVRational out_tb);
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/**
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* Add a value to a timestamp.
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*
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* This function guarantees that when the same value is repeatly added that
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* no accumulation of rounding errors occurs.
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*
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* @param ts Input timestamp
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* @param ts_tb Input timestamp timebase
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* @param inc value to add to ts
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* @param inc_tb inc timebase
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*/
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int64_t av_add_stable(AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t inc);
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/**
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* @}
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*/
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#endif /* AVUTIL_MATHEMATICS_H */
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