mirror of https://github.com/mpv-player/mpv.git
misc/random: add xoshiro random number implementation
Add xoshiro as a PRNG implementation instead of relying on srand() and rand() from the C standard library. This, in particular, lets us avoid platform-defined behavior with respect to threading.
This commit is contained in:
parent
813164cc07
commit
52e7269ea6
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@ -21,6 +21,7 @@
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#include "common/common.h"
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#include "common/common.h"
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#include "common/global.h"
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#include "common/global.h"
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#include "common/msg.h"
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#include "common/msg.h"
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#include "misc/random.h"
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#include "mpv_talloc.h"
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#include "mpv_talloc.h"
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#include "options/path.h"
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#include "options/path.h"
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@ -147,7 +148,7 @@ void playlist_shuffle(struct playlist *pl)
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for (int n = 0; n < pl->num_entries; n++)
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for (int n = 0; n < pl->num_entries; n++)
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pl->entries[n]->original_index = n;
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pl->entries[n]->original_index = n;
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for (int n = 0; n < pl->num_entries - 1; n++) {
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for (int n = 0; n < pl->num_entries - 1; n++) {
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int j = (int)((double)(pl->num_entries - n) * rand() / (RAND_MAX + 1.0));
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size_t j = (size_t)((pl->num_entries - n) * mp_rand_next_double());
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MPSWAP(struct playlist_entry *, pl->entries[n], pl->entries[n + j]);
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MPSWAP(struct playlist_entry *, pl->entries[n], pl->entries[n + j]);
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}
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}
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playlist_update_indexes(pl, 0, -1);
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playlist_update_indexes(pl, 0, -1);
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@ -152,8 +152,6 @@ extern "C" {
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* - Using UNIX IPC (off by default) will override the SIGPIPE signal handler,
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* - Using UNIX IPC (off by default) will override the SIGPIPE signal handler,
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* and set it to SIG_IGN. Some invocations of the "subprocess" command will
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* and set it to SIG_IGN. Some invocations of the "subprocess" command will
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* also do that.
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* also do that.
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* - mpv will reseed the legacy C random number generator by calling srand() at
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* some random point once.
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* - mpv may start sub processes, so overriding SIGCHLD, or waiting on all PIDs
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* - mpv may start sub processes, so overriding SIGCHLD, or waiting on all PIDs
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* (such as calling wait()) by the parent process or any other library within
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* (such as calling wait()) by the parent process or any other library within
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* the process must be avoided. libmpv itself only waits for its own PIDs.
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* the process must be avoided. libmpv itself only waits for its own PIDs.
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@ -134,6 +134,7 @@ sources = files(
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'misc/json.c',
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'misc/json.c',
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'misc/natural_sort.c',
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'misc/natural_sort.c',
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'misc/node.c',
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'misc/node.c',
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'misc/random.c',
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'misc/rendezvous.c',
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'misc/rendezvous.c',
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'misc/thread_pool.c',
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'misc/thread_pool.c',
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'misc/thread_tools.c',
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'misc/thread_tools.c',
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@ -0,0 +1,75 @@
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/*
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* Implementation of non-cryptographic pseudo-random number
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* generator algorithm known as xoshiro.
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*
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* This file is part of mpv.
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*
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* mpv is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* mpv is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdint.h>
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#include <pthread.h>
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#include "random.h"
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static uint64_t state[4];
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static pthread_mutex_t state_mutex = PTHREAD_MUTEX_INITIALIZER;
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static inline uint64_t rotl_u64(const uint64_t x, const int k)
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{
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return (x << k) | (x >> (64 - k));
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}
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static inline uint64_t splitmix64(uint64_t *const x)
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{
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uint64_t z = (*x += UINT64_C(0x9e3779b97f4a7c15));
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z = (z ^ (z >> 30)) * UINT64_C(0xbf58476d1ce4e5b9);
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z = (z ^ (z >> 27)) * UINT64_C(0x94d049bb133111eb);
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return z ^ (z >> 31);
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}
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void mp_rand_seed(uint64_t seed)
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{
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pthread_mutex_lock(&state_mutex);
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state[0] = seed;
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for (int i = 1; i < 4; i++)
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state[i] = splitmix64(&seed);
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pthread_mutex_unlock(&state_mutex);
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}
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uint64_t mp_rand_next(void)
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{
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uint64_t result, t;
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pthread_mutex_lock(&state_mutex);
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result = rotl_u64(state[1] * 5, 7) * 9;
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t = state[1] << 17;
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state[2] ^= state[0];
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state[3] ^= state[1];
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state[1] ^= state[2];
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state[0] ^= state[3];
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state[2] ^= t;
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state[3] = rotl_u64(state[3], 45);
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pthread_mutex_unlock(&state_mutex);
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return result;
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}
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double mp_rand_next_double(void)
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{
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return (mp_rand_next() >> 11) * 0x1.0p-53;
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}
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@ -0,0 +1,41 @@
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/*
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* Implementation of non-cryptographic pseudo-random number
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* generator algorithm known as xoshiro.
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*
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* This file is part of mpv.
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*
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* mpv is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* mpv is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <stdint.h>
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/*
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* Initialize the pseudo-random number generator's state with
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* the given 64-bit seed.
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*/
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void mp_rand_seed(uint64_t seed);
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/*
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* Return the next 64-bit psuedo-random integer, and update the state
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* accordingly.
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*/
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uint64_t mp_rand_next(void);
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/*
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* Return a double value in the range of [0.0, 1.0) with uniform
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* distribution, and update the state accordingly.
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*/
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double mp_rand_next_double(void);
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@ -32,6 +32,7 @@
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#include "mpv_talloc.h"
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#include "mpv_talloc.h"
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#include "config.h"
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#include "config.h"
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#include "misc/random.h"
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#include "osdep/io.h"
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#include "osdep/io.h"
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#include "osdep/terminal.h"
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#include "osdep/terminal.h"
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@ -804,7 +805,7 @@ int mp_mkostemps(char *template, int suffixlen, int flags)
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for (size_t fuckshit = 0; fuckshit < UINT32_MAX; fuckshit++) {
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for (size_t fuckshit = 0; fuckshit < UINT32_MAX; fuckshit++) {
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// Using a random value may make it require fewer iterations (even if
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// Using a random value may make it require fewer iterations (even if
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// not truly random; just a counter would be sufficient).
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// not truly random; just a counter would be sufficient).
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size_t fuckmess = rand();
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size_t fuckmess = mp_rand_next();
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char crap[7] = "";
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char crap[7] = "";
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snprintf(crap, sizeof(crap), "%06zx", fuckmess);
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snprintf(crap, sizeof(crap), "%06zx", fuckmess);
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memcpy(t, crap, 6);
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memcpy(t, crap, 6);
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@ -25,6 +25,7 @@
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#include "common/common.h"
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#include "common/common.h"
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#include "common/msg.h"
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#include "common/msg.h"
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#include "misc/random.h"
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#include "timer.h"
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#include "timer.h"
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static uint64_t raw_time_offset;
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static uint64_t raw_time_offset;
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@ -33,7 +34,7 @@ static pthread_once_t timer_init_once = PTHREAD_ONCE_INIT;
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static void do_timer_init(void)
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static void do_timer_init(void)
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{
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{
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mp_raw_time_init();
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mp_raw_time_init();
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srand(mp_raw_time_us());
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mp_rand_seed(mp_raw_time_us());
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raw_time_offset = mp_raw_time_us();
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raw_time_offset = mp_raw_time_us();
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// Arbitrary additional offset to avoid confusing relative/absolute times.
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// Arbitrary additional offset to avoid confusing relative/absolute times.
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// Also,we rule that the timer never returns 0 (so default-initialized
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// Also,we rule that the timer never returns 0 (so default-initialized
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@ -335,6 +335,7 @@ def build(ctx):
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( "misc/natural_sort.c" ),
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( "misc/natural_sort.c" ),
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( "misc/node.c" ),
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( "misc/node.c" ),
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( "misc/rendezvous.c" ),
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( "misc/rendezvous.c" ),
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( "misc/random.c" ),
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( "misc/thread_pool.c" ),
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( "misc/thread_pool.c" ),
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( "misc/thread_tools.c" ),
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( "misc/thread_tools.c" ),
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