mirror of
https://github.com/Atmosphere-NX/Atmosphere.git
synced 2024-11-18 01:46:47 +00:00
99 lines
No EOL
3.8 KiB
C++
99 lines
No EOL
3.8 KiB
C++
/*
|
|
* Copyright (c) 2018-2020 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/>.
|
|
*/
|
|
|
|
#pragma once
|
|
#include <vapours.hpp>
|
|
|
|
namespace ams::util {
|
|
|
|
/* Implementation of TinyMT (mersenne twister RNG). */
|
|
/* Like Nintendo, we will use the sample parameters. */
|
|
class TinyMT {
|
|
public:
|
|
static constexpr size_t NumStateWords = 4;
|
|
|
|
struct State {
|
|
u32 data[NumStateWords];
|
|
};
|
|
private:
|
|
static constexpr u32 ParamMat1 = 0x8F7011EE;
|
|
static constexpr u32 ParamMat2 = 0xFC78FF1F;
|
|
static constexpr u32 ParamTmat = 0x3793FDFF;
|
|
|
|
static constexpr u32 ParamMult = 0x6C078965;
|
|
static constexpr u32 ParamPlus = 0x0019660D;
|
|
static constexpr u32 ParamXor = 0x5D588B65;
|
|
|
|
static constexpr u32 TopBitmask = 0x7FFFFFFF;
|
|
|
|
static constexpr int MinimumInitIterations = 8;
|
|
static constexpr int NumDiscardedInitOutputs = 8;
|
|
private:
|
|
State state;
|
|
private:
|
|
/* Internal API. */
|
|
void FinalizeInitialization();
|
|
|
|
u32 GenerateRandomU24() { return (this->GenerateRandomU32() >> 8); }
|
|
|
|
static void GenerateInitialValuePlus(TinyMT::State *state, int index, u32 value);
|
|
static void GenerateInitialValueXor(TinyMT::State *state, int index);
|
|
public:
|
|
/* Public API. */
|
|
|
|
/* Initialization. */
|
|
void Initialize(u32 seed);
|
|
void Initialize(const u32 *seed, int seed_count);
|
|
|
|
/* State management. */
|
|
void GetState(TinyMT::State *out) const;
|
|
void SetState(const TinyMT::State *state);
|
|
|
|
/* Random generation. */
|
|
void GenerateRandomBytes(void *dst, size_t size);
|
|
u32 GenerateRandomU32();
|
|
|
|
inline u64 GenerateRandomU64() {
|
|
const u32 lo = this->GenerateRandomU32();
|
|
const u32 hi = this->GenerateRandomU32();
|
|
return (static_cast<u64>(hi) << 32) | static_cast<u64>(lo);
|
|
}
|
|
|
|
inline float GenerateRandomF32() {
|
|
/* Floats have 24 bits of mantissa. */
|
|
constexpr int MantissaBits = 24;
|
|
return GenerateRandomU24() * (1.0f / (1ul << MantissaBits));
|
|
}
|
|
|
|
inline double GenerateRandomF64() {
|
|
/* Doubles have 53 bits of mantissa. */
|
|
/* The smart way to generate 53 bits of random would be to use 32 bits */
|
|
/* from the first rnd32() call, and then 21 from the second. */
|
|
/* Nintendo does not. They use (32 - 5) = 27 bits from the first rnd32() */
|
|
/* call, and (32 - 6) bits from the second. We'll do what they do, but */
|
|
/* There's not a clear reason why. */
|
|
constexpr int MantissaBits = 53;
|
|
constexpr int Shift1st = (64 - MantissaBits) / 2;
|
|
constexpr int Shift2nd = (64 - MantissaBits) - Shift1st;
|
|
|
|
const u32 first = (this->GenerateRandomU32() >> Shift1st);
|
|
const u32 second = (this->GenerateRandomU32() >> Shift2nd);
|
|
|
|
return (1.0 * first * (1ul << (32 - Shift2nd)) + second) * (1.0 / (1ul << MantissaBits));
|
|
}
|
|
};
|
|
|
|
} |