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/*
* Mersenne Twister Random 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
*/
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# ifndef FFMPEG_RANDOM_H
# define FFMPEG_RANDOM_H
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# define AV_RANDOM_N 624
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 ;
void av_init_random ( unsigned int seed , AVRandomState * state ) ; ///< to be inlined, the struct must be visible, so it doesn't 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 on [0,0xffffffff]-interval */
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 ;
}
/** return random in 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 ) ;
}
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# endif /* FFMPEG_RANDOM_H */