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