| 1 | /*
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| 2 | * Mersenne Twister Random Algorithm
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| 3 | * Copyright (c) 2006 Ryan Martell.
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| 4 | * Based on A C-program for MT19937, with initialization improved 2002/1/26. Coded by
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| 5 | * Takuji Nishimura and Makoto Matsumoto.
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| 6 | *
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| 7 | * This file is part of FFmpeg.
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| 8 | *
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| 9 | * FFmpeg is free software; you can redistribute it and/or
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| 10 | * modify it under the terms of the GNU Lesser General Public
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| 11 | * License as published by the Free Software Foundation; either
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| 12 | * version 2.1 of the License, or (at your option) any later version.
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| 13 | *
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| 14 | * FFmpeg is distributed in the hope that it will be useful,
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| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 17 | * Lesser General Public License for more details.
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| 18 | *
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| 19 | * You should have received a copy of the GNU Lesser General Public
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| 20 | * License along with FFmpeg; if not, write to the Free Software
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| 21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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| 22 | */
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| 23 |
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| 24 | #ifndef AV_RANDOM_H
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| 25 | #define AV_RANDOM_H
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| 26 |
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| 27 | #define AV_RANDOM_N 624
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| 28 |
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| 29 | typedef struct {
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| 30 | unsigned int mt[AV_RANDOM_N]; ///< the array for the state vector
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| 31 | int index; ///< current untempered value we use as the base.
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| 32 | } AVRandomState;
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| 33 |
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| 34 |
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| 35 | 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
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| 36 | void av_random_generate_untempered_numbers(AVRandomState *state); ///< Regenerate the untempered numbers (must be done every 624 iterations, or it will loop)
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| 37 |
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| 38 | /** generates a random number on [0,0xffffffff]-interval */
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| 39 | static inline unsigned int av_random(AVRandomState *state)
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| 40 | {
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| 41 | unsigned int y;
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| 42 |
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| 43 | // regenerate the untempered numbers if we should...
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| 44 | if (state->index >= AV_RANDOM_N)
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| 45 | av_random_generate_untempered_numbers(state);
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| 46 |
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| 47 | // grab one...
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| 48 | y = state->mt[state->index++];
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| 49 |
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| 50 | /* Now temper (Mersenne Twister coefficients) The coefficients for MT19937 are.. */
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| 51 | y ^= (y >> 11);
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| 52 | y ^= (y << 7) & 0x9d2c5680;
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| 53 | y ^= (y << 15) & 0xefc60000;
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| 54 | y ^= (y >> 18);
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| 55 |
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| 56 | return y;
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| 57 | }
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| 58 |
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| 59 | /** return random in range [0-1] as double */
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| 60 | static inline double av_random_real1(AVRandomState *state)
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| 61 | {
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| 62 | /* divided by 2^32-1 */
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| 63 | return av_random(state) * (1.0 / 4294967296.0);
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| 64 | }
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| 65 |
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| 66 | // only available if DEBUG is defined in the .c file
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| 67 | void av_benchmark_random(void);
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| 68 | #endif // AV_RANDOM_H
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| 69 |
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