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/*
* Implementation of non-cryptographic pseudo-random number
* generator algorithm known as xoshiro.
*
* This file is part of mpv.
*
* mpv 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.
*
* mpv 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 mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdint.h>
#include "osdep/threads.h"
#include "random.h"
static uint64_t state[4];
static mp_static_mutex state_mutex = MP_STATIC_MUTEX_INITIALIZER;
static inline uint64_t rotl_u64(const uint64_t x, const int k)
{
return (x << k) | (x >> (64 - k));
}
static inline uint64_t splitmix64(uint64_t *const x)
{
uint64_t z = (*x += UINT64_C(0x9e3779b97f4a7c15));
z = (z ^ (z >> 30)) * UINT64_C(0xbf58476d1ce4e5b9);
z = (z ^ (z >> 27)) * UINT64_C(0x94d049bb133111eb);
return z ^ (z >> 31);
}
void mp_rand_seed(uint64_t seed)
{
mp_mutex_lock(&state_mutex);
state[0] = seed;
for (int i = 1; i < 4; i++)
state[i] = splitmix64(&seed);
mp_mutex_unlock(&state_mutex);
}
uint64_t mp_rand_next(void)
{
uint64_t result, t;
mp_mutex_lock(&state_mutex);
result = rotl_u64(state[1] * 5, 7) * 9;
t = state[1] << 17;
state[2] ^= state[0];
state[3] ^= state[1];
state[1] ^= state[2];
state[0] ^= state[3];
state[2] ^= t;
state[3] = rotl_u64(state[3], 45);
mp_mutex_unlock(&state_mutex);
return result;
}
double mp_rand_next_double(void)
{
return (mp_rand_next() >> 11) * 0x1.0p-53;
}
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