mirror of
https://github.com/Atmosphere-NX/Atmosphere
synced 2024-09-20 07:08:59 +00:00
99 lines
3.8 KiB
C++
99 lines
3.8 KiB
C++
/*
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* Copyright (c) 2018-2019 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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#pragma once
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#include <vapours.hpp>
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namespace ams::util {
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/* Implementation of TinyMT (mersenne twister RNG). */
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/* Like Nintendo, we will use the sample parameters. */
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class TinyMT {
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public:
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static constexpr size_t NumStateWords = 4;
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struct State {
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u32 data[NumStateWords];
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};
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private:
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static constexpr u32 ParamMat1 = 0x8F7011EE;
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static constexpr u32 ParamMat2 = 0xFC78FF1F;
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static constexpr u32 ParamTmat = 0x3793FDFF;
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static constexpr u32 ParamMult = 0x6C078965;
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static constexpr u32 ParamPlus = 0x0019660D;
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static constexpr u32 ParamXor = 0x5D588B65;
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static constexpr u32 TopBitmask = 0x7FFFFFFF;
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static constexpr int MinimumInitIterations = 8;
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static constexpr int NumDiscardedInitOutputs = 8;
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private:
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State state;
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private:
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/* Internal API. */
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void FinalizeInitialization();
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u32 GenerateRandomU24() { return (this->GenerateRandomU32() >> 8); }
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static void GenerateInitialValuePlus(TinyMT::State *state, int index, u32 value);
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static void GenerateInitialValueXor(TinyMT::State *state, int index);
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public:
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/* Public API. */
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/* Initialization. */
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void Initialize(u32 seed);
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void Initialize(const u32 *seed, int seed_count);
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/* State management. */
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void GetState(TinyMT::State *out) const;
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void SetState(const TinyMT::State *state);
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/* Random generation. */
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void GenerateRandomBytes(void *dst, size_t size);
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u32 GenerateRandomU32();
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inline u64 GenerateRandomU64() {
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const u32 lo = this->GenerateRandomU32();
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const u32 hi = this->GenerateRandomU32();
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return (static_cast<u64>(hi) << 32) | static_cast<u64>(lo);
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}
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inline float GenerateRandomF32() {
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/* Floats have 24 bits of mantissa. */
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constexpr int MantissaBits = 24;
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return GenerateRandomU24() * (1.0f / (1ul << MantissaBits));
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}
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inline double GenerateRandomF64() {
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/* Doubles have 53 bits of mantissa. */
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/* The smart way to generate 53 bits of random would be to use 32 bits */
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/* from the first rnd32() call, and then 21 from the second. */
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/* Nintendo does not. They use (32 - 5) = 27 bits from the first rnd32() */
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/* call, and (32 - 6) bits from the second. We'll do what they do, but */
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/* There's not a clear reason why. */
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constexpr int MantissaBits = 53;
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constexpr int Shift1st = (64 - MantissaBits) / 2;
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constexpr int Shift2nd = (64 - MantissaBits) - Shift1st;
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const u32 first = (this->GenerateRandomU32() >> Shift1st);
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const u32 second = (this->GenerateRandomU32() >> Shift2nd);
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return (1.0 * first * (1ul << (32 - Shift2nd)) + second) * (1.0 / (1ul << MantissaBits));
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}
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};
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} |