Atmosphere/libraries/libstratosphere/source/os/os_random.cpp

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/*
* Copyright (c) Atmosphère-NX
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*
* 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 <stratosphere.hpp>
#include "impl/os_random_impl.hpp"
namespace ams::os {
namespace {
constinit util::TinyMT g_random;
constinit os::SdkMutex g_random_mutex;
constinit bool g_initialized_random;
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template<typename T>
inline T GenerateRandomTImpl(T max) {
static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value);
const T EffectiveMax = (std::numeric_limits<T>::max() / max) * max;
T cur_rnd;
while (true) {
os::GenerateRandomBytes(&cur_rnd, sizeof(T));
if (cur_rnd < EffectiveMax) {
return cur_rnd % max;
}
}
}
}
void GenerateRandomBytes(void *dst, size_t size) {
std::scoped_lock lk(g_random_mutex);
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if (AMS_UNLIKELY(!g_initialized_random)) {
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impl::InitializeRandomImpl(&g_random);
g_initialized_random = true;
}
g_random.GenerateRandomBytes(dst, size);
}
u32 GenerateRandomU32(u32 max) {
return GenerateRandomTImpl<u32>(max);
}
u64 GenerateRandomU64(u64 max) {
return GenerateRandomTImpl<u64>(max);
}
}