mirror of
https://github.com/Atmosphere-NX/Atmosphere-libs.git
synced 2025-10-31 11:36:02 +01:00
248 lines
9.7 KiB
C++
248 lines
9.7 KiB
C++
/*
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* Copyright (c) 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/common.hpp>
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#include <vapours/assert.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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static constexpr inline u32 XorByShifted27(u32 value) {
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return value ^ (value >> 27);
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}
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static constexpr inline u32 XorByShifted30(u32 value) {
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return value ^ (value >> 30);
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}
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private:
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State m_state;
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private:
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/* Internal API. */
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void FinalizeInitialization() {
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const u32 state0 = m_state.data[0] & TopBitmask;
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const u32 state1 = m_state.data[1];
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const u32 state2 = m_state.data[2];
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const u32 state3 = m_state.data[3];
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if (state0 == 0 && state1 == 0 && state2 == 0 && state3 == 0) {
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m_state.data[0] = 'T';
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m_state.data[1] = 'I';
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m_state.data[2] = 'N';
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m_state.data[3] = 'Y';
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}
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for (int i = 0; i < NumDiscardedInitOutputs; i++) {
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this->GenerateRandomU32();
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}
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}
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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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u32 &state0 = state->data[(index + 0) % NumStateWords];
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u32 &state1 = state->data[(index + 1) % NumStateWords];
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u32 &state2 = state->data[(index + 2) % NumStateWords];
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u32 &state3 = state->data[(index + 3) % NumStateWords];
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const u32 x = XorByShifted27(state0 ^ state1 ^ state3) * ParamPlus;
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const u32 y = x + index + value;
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state0 = y;
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state1 += x;
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state2 += y;
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}
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static void GenerateInitialValueXor(TinyMT::State *state, int index) {
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u32 &state0 = state->data[(index + 0) % NumStateWords];
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u32 &state1 = state->data[(index + 1) % NumStateWords];
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u32 &state2 = state->data[(index + 2) % NumStateWords];
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u32 &state3 = state->data[(index + 3) % NumStateWords];
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const u32 x = XorByShifted27(state0 + state1 + state3) * ParamXor;
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const u32 y = x - index;
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state0 = y;
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state1 ^= x;
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state2 ^= y;
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}
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public:
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constexpr explicit TinyMT(util::ConstantInitializeTag) : m_state() { /* ... */ }
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explicit TinyMT() { /* ... */ }
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/* Initialization. */
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void Initialize(u32 seed) {
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m_state.data[0] = seed;
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m_state.data[1] = ParamMat1;
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m_state.data[2] = ParamMat2;
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m_state.data[3] = ParamTmat;
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for (int i = 1; i < MinimumInitIterations; i++) {
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const u32 mixed = XorByShifted30(m_state.data[(i - 1) % NumStateWords]);
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m_state.data[i % NumStateWords] ^= mixed * ParamMult + i;
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}
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this->FinalizeInitialization();
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}
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void Initialize(const u32 *seed, int seed_count) {
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m_state.data[0] = 0;
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m_state.data[1] = ParamMat1;
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m_state.data[2] = ParamMat2;
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m_state.data[3] = ParamTmat;
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{
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const int num_init_iterations = std::max(seed_count + 1, MinimumInitIterations) - 1;
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GenerateInitialValuePlus(std::addressof(m_state), 0, seed_count);
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for (int i = 0; i < num_init_iterations; i++) {
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GenerateInitialValuePlus(std::addressof(m_state), (i + 1) % NumStateWords, (i < seed_count) ? seed[i] : 0);
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}
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for (int i = 0; i < static_cast<int>(NumStateWords); i++) {
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GenerateInitialValueXor(std::addressof(m_state), (i + 1 + num_init_iterations) % NumStateWords);
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}
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}
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this->FinalizeInitialization();
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}
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/* State management. */
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void GetState(TinyMT::State *out) const {
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std::memcpy(out->data, m_state.data, sizeof(m_state));
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}
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void SetState(const TinyMT::State *state) {
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std::memcpy(m_state.data, state->data, sizeof(m_state));
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}
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/* Random generation. */
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NOINLINE void GenerateRandomBytes(void *dst, size_t size) {
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const uintptr_t start = reinterpret_cast<uintptr_t>(dst);
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const uintptr_t end = start + size;
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const uintptr_t aligned_start = util::AlignUp(start, 4);
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const uintptr_t aligned_end = util::AlignDown(end, 4);
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/* Make sure we're aligned. */
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if (start < aligned_start) {
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const u32 rnd = this->GenerateRandomU32();
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std::memcpy(dst, std::addressof(rnd), aligned_start - start);
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}
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/* Write as many aligned u32s as we can. */
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{
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u32 * cur_dst = reinterpret_cast<u32 *>(aligned_start);
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u32 * const end_dst = reinterpret_cast<u32 *>(aligned_end);
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while (cur_dst < end_dst) {
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*(cur_dst++) = this->GenerateRandomU32();
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}
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}
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/* Handle any leftover unaligned data. */
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if (aligned_end < end) {
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const u32 rnd = this->GenerateRandomU32();
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std::memcpy(reinterpret_cast<void *>(aligned_end), std::addressof(rnd), end - aligned_end);
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}
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}
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NOINLINE u32 GenerateRandomU32() {
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/* Advance state. */
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const u32 x0 = (m_state.data[0] & TopBitmask) ^ m_state.data[1] ^ m_state.data[2];
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const u32 y0 = m_state.data[3];
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const u32 x1 = x0 ^ (x0 << 1);
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const u32 y1 = y0 ^ (y0 >> 1) ^ x1;
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const u32 state0 = m_state.data[1];
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u32 state1 = m_state.data[2];
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u32 state2 = x1 ^ (y1 << 10);
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const u32 state3 = y1;
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if ((y1 & 1) != 0) {
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state1 ^= ParamMat1;
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state2 ^= ParamMat2;
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}
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m_state.data[0] = state0;
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m_state.data[1] = state1;
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m_state.data[2] = state2;
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m_state.data[3] = state3;
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/* Temper. */
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const u32 t1 = state0 + (state2 >> 8);
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u32 t0 = state3 ^ t1;
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if ((t1 & 1) != 0) {
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t0 ^= ParamTmat;
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}
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return t0;
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}
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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 * (static_cast<u64>(1) << (32 - Shift2nd)) + second) * (1.0 / (static_cast<u64>(1) << MantissaBits));
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}
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};
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} |