mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-11-26 19:01:44 +02:00
80 lines
2.8 KiB
C
80 lines
2.8 KiB
C
/*
|
|
* Mersenne Twister PRNG algorithm
|
|
* Copyright (c) 2006 Ryan Martell
|
|
* Based on a C program for MT19937, with initialization improved 2002/1/26.
|
|
* Coded by Takuji Nishimura and Makoto Matsumoto.
|
|
*
|
|
* 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
|
|
*/
|
|
|
|
#ifndef AVUTIL_RANDOM_H
|
|
#define AVUTIL_RANDOM_H
|
|
|
|
#define AV_RANDOM_N 624
|
|
|
|
#include "avutil.h"
|
|
#include "common.h"
|
|
|
|
typedef struct {
|
|
unsigned int mt[AV_RANDOM_N]; ///< the array for the state vector
|
|
int index; ///< Current untempered value we use as the base.
|
|
} AVRandomState;
|
|
|
|
|
|
#if LIBAVUTIL_VERSION_MAJOR < 50
|
|
attribute_deprecated void av_init_random(unsigned int seed, AVRandomState *state);
|
|
#endif
|
|
void av_random_init(AVRandomState *state, unsigned int seed); ///< To be inlined, the struct must be visible. So it does not make sense to try and keep it opaque with malloc/free-like calls.
|
|
void av_random_generate_untempered_numbers(AVRandomState *state); ///< Regenerate the untempered numbers (must be done every 624 iterations, or it will loop).
|
|
|
|
/**
|
|
* Generates a random number from the interval [0,0xffffffff].
|
|
*
|
|
* Please do NOT use the Mersenne Twister, it is slow. Use the random number
|
|
* generator from lfg.c/h or a simple LCG like state = state*1664525+1013904223.
|
|
* If you still choose to use MT, expect that you will have to provide
|
|
* some evidence that it makes a difference for the case where you use it.
|
|
*/
|
|
static inline unsigned int av_random(AVRandomState *state)
|
|
{
|
|
unsigned int y;
|
|
|
|
// Regenerate the untempered numbers if we should...
|
|
if (state->index >= AV_RANDOM_N)
|
|
av_random_generate_untempered_numbers(state);
|
|
|
|
// Grab one...
|
|
y = state->mt[state->index++];
|
|
|
|
/* Now temper (Mersenne Twister coefficients). The coefficients for MT19937 are.. */
|
|
y ^= (y >> 11);
|
|
y ^= (y << 7) & 0x9d2c5680;
|
|
y ^= (y << 15) & 0xefc60000;
|
|
y ^= (y >> 18);
|
|
|
|
return y;
|
|
}
|
|
|
|
/** Returns a random number in the range [0-1] as double. */
|
|
static inline double av_random_real1(AVRandomState *state)
|
|
{
|
|
/* divided by 2^32-1 */
|
|
return av_random(state) * (1.0 / 4294967296.0);
|
|
}
|
|
|
|
#endif /* AVUTIL_RANDOM_H */
|