mirror of
https://github.com/Atmosphere-NX/Atmosphere.git
synced 2024-11-05 19:51:45 +00:00
65 lines
1.8 KiB
C++
65 lines
1.8 KiB
C++
/*
|
|
* Copyright (c) 2018 Atmosphère-NX
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify it
|
|
* under the terms and conditions of the GNU General Public License,
|
|
* version 2, as published by the Free Software Foundation.
|
|
*
|
|
* This program is distributed in the hope it will be useful, but WITHOUT
|
|
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
|
|
* more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include <switch.h>
|
|
|
|
#include "ldr_random.hpp"
|
|
|
|
/* Official HOS uses TinyMT. This is high effort. Let's just use XorShift. */
|
|
/* https://en.wikipedia.org/wiki/Xorshift */
|
|
|
|
static u32 g_random_state[4] = {0};
|
|
static bool g_has_initialized = false;
|
|
|
|
static void EnsureRandomState() {
|
|
if (g_has_initialized) {
|
|
return;
|
|
}
|
|
|
|
/* Retrieve process entropy with svcGetInfo. */
|
|
u64 val = 0;
|
|
for (unsigned int i = 0; i < 4; i++) {
|
|
if (R_FAILED(svcGetInfo(&val, 0xB, 0, i))) {
|
|
/* TODO: Panic? */
|
|
}
|
|
g_random_state[i] = val & 0xFFFFFFFF;
|
|
}
|
|
|
|
g_has_initialized = true;
|
|
}
|
|
|
|
u32 RandomUtils::GetNext() {
|
|
EnsureRandomState();
|
|
u32 s, t = g_random_state[3];
|
|
t ^= t << 11;
|
|
t ^= t >> 8;
|
|
g_random_state[3] = g_random_state[2]; g_random_state[2] = g_random_state[1]; g_random_state[1] = (s = g_random_state[0]);
|
|
t ^= s;
|
|
t ^= s >> 19;
|
|
g_random_state[0] = t;
|
|
return t;
|
|
}
|
|
|
|
/* These are slightly biased, but I think that's totally okay. */
|
|
u32 RandomUtils::GetRandomU32(u32 max) {
|
|
return GetNext() % max;
|
|
}
|
|
|
|
u64 RandomUtils::GetRandomU64(u64 max) {
|
|
u64 val = GetNext();
|
|
val |= ((u64)GetNext()) << 32;
|
|
return val % max;
|
|
}
|