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🎥 Command line media player
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103/* * 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 <libavutil/random_seed.h>
#include "common/common.h"#include "misc/mp_assert.h"#include "osdep/timer.h"#include "random.h"
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);}
mp_rand_state mp_rand_seed(uint64_t seed){ mp_rand_state ret;
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION seed = 42;#endif
if (seed == 0) { if (av_random_bytes((void *)ret.v, sizeof(ret.v)) == 0) { return ret; } seed = mp_raw_time_ns(); seed ^= (uintptr_t)&mp_rand_seed; // ASLR, hopefully seed += (uintptr_t)&ret; // stack position }
ret.v[0] = seed; for (int i = 1; i < 4; i++) ret.v[i] = splitmix64(&seed); return ret;}
uint64_t mp_rand_next(mp_rand_state *s){ uint64_t result, t; uint64_t *state = s->v;
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);
return result;}
double mp_rand_next_double(mp_rand_state *s){ return (mp_rand_next(s) >> 11) * 0x1.0p-53;}
// <https://web.archive.org/web/20250321082025/// https://www.pcg-random.org/posts/bounded-rands.html#bitmask-with-rejection-unbiased-apples-method>uint32_t mp_rand_in_range32(mp_rand_state *s, uint32_t min, uint32_t max){ mp_assert(min < max); uint32_t range = max - min; uint32_t mask = mp_round_next_power_of_2(range) - 1; uint32_t ret; do { ret = mp_rand_next(s) & mask; } while (ret >= range); return min + ret;}