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-rw-r--r--src/common/CMakeLists.txt1
-rw-r--r--src/common/tiny_mt.h250
2 files changed, 251 insertions, 0 deletions
diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index b657506b1..788516ded 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -167,6 +167,7 @@ add_library(common STATIC
threadsafe_queue.h
time_zone.cpp
time_zone.h
+ tiny_mt.h
tree.h
uint128.h
uuid.cpp
diff --git a/src/common/tiny_mt.h b/src/common/tiny_mt.h
new file mode 100644
index 000000000..19ae5b7d6
--- /dev/null
+++ b/src/common/tiny_mt.h
@@ -0,0 +1,250 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+
+#include "common/alignment.h"
+#include "common/common_types.h"
+
+namespace Common {
+
+// Implementation of TinyMT (mersenne twister RNG).
+// Like Nintendo, we will use the sample parameters.
+class TinyMT {
+public:
+ static constexpr std::size_t NumStateWords = 4;
+
+ struct State {
+ std::array<u32, NumStateWords> data{};
+ };
+
+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;
+
+ static constexpr u32 XorByShifted27(u32 value) {
+ return value ^ (value >> 27);
+ }
+
+ static constexpr u32 XorByShifted30(u32 value) {
+ return value ^ (value >> 30);
+ }
+
+private:
+ State state{};
+
+private:
+ // Internal API.
+ void FinalizeInitialization() {
+ const u32 state0 = this->state.data[0] & TopBitmask;
+ const u32 state1 = this->state.data[1];
+ const u32 state2 = this->state.data[2];
+ const u32 state3 = this->state.data[3];
+
+ if (state0 == 0 && state1 == 0 && state2 == 0 && state3 == 0) {
+ this->state.data[0] = 'T';
+ this->state.data[1] = 'I';
+ this->state.data[2] = 'N';
+ this->state.data[3] = 'Y';
+ }
+
+ for (int i = 0; i < NumDiscardedInitOutputs; i++) {
+ this->GenerateRandomU32();
+ }
+ }
+
+ u32 GenerateRandomU24() {
+ return (this->GenerateRandomU32() >> 8);
+ }
+
+ static void GenerateInitialValuePlus(TinyMT::State* state, int index, u32 value) {
+ u32& state0 = state->data[(index + 0) % NumStateWords];
+ u32& state1 = state->data[(index + 1) % NumStateWords];
+ u32& state2 = state->data[(index + 2) % NumStateWords];
+ u32& state3 = state->data[(index + 3) % NumStateWords];
+
+ const u32 x = XorByShifted27(state0 ^ state1 ^ state3) * ParamPlus;
+ const u32 y = x + index + value;
+
+ state0 = y;
+ state1 += x;
+ state2 += y;
+ }
+
+ static void GenerateInitialValueXor(TinyMT::State* state, int index) {
+ u32& state0 = state->data[(index + 0) % NumStateWords];
+ u32& state1 = state->data[(index + 1) % NumStateWords];
+ u32& state2 = state->data[(index + 2) % NumStateWords];
+ u32& state3 = state->data[(index + 3) % NumStateWords];
+
+ const u32 x = XorByShifted27(state0 + state1 + state3) * ParamXor;
+ const u32 y = x - index;
+
+ state0 = y;
+ state1 ^= x;
+ state2 ^= y;
+ }
+
+public:
+ constexpr TinyMT() = default;
+
+ // Public API.
+
+ // Initialization.
+ void Initialize(u32 seed) {
+ this->state.data[0] = seed;
+ this->state.data[1] = ParamMat1;
+ this->state.data[2] = ParamMat2;
+ this->state.data[3] = ParamTmat;
+
+ for (int i = 1; i < MinimumInitIterations; i++) {
+ const u32 mixed = XorByShifted30(this->state.data[(i - 1) % NumStateWords]);
+ this->state.data[i % NumStateWords] ^= mixed * ParamMult + i;
+ }
+
+ this->FinalizeInitialization();
+ }
+
+ void Initialize(const u32* seed, int seed_count) {
+ this->state.data[0] = 0;
+ this->state.data[1] = ParamMat1;
+ this->state.data[2] = ParamMat2;
+ this->state.data[3] = ParamTmat;
+
+ {
+ const int num_init_iterations = std::max(seed_count + 1, MinimumInitIterations) - 1;
+
+ GenerateInitialValuePlus(&this->state, 0, seed_count);
+
+ for (int i = 0; i < num_init_iterations; i++) {
+ GenerateInitialValuePlus(&this->state, (i + 1) % NumStateWords,
+ (i < seed_count) ? seed[i] : 0);
+ }
+
+ for (int i = 0; i < static_cast<int>(NumStateWords); i++) {
+ GenerateInitialValueXor(&this->state,
+ (i + 1 + num_init_iterations) % NumStateWords);
+ }
+ }
+
+ this->FinalizeInitialization();
+ }
+
+ // State management.
+ void GetState(TinyMT::State& out) const {
+ out.data = this->state.data;
+ }
+
+ void SetState(const TinyMT::State& state_) {
+ this->state.data = state_.data;
+ }
+
+ // Random generation.
+ void GenerateRandomBytes(void* dst, std::size_t size) {
+ const uintptr_t start = reinterpret_cast<uintptr_t>(dst);
+ const uintptr_t end = start + size;
+ const uintptr_t aligned_start = Common::AlignUp(start, 4);
+ const uintptr_t aligned_end = Common::AlignDown(end, 4);
+
+ // Make sure we're aligned.
+ if (start < aligned_start) {
+ const u32 rnd = this->GenerateRandomU32();
+ std::memcpy(dst, &rnd, aligned_start - start);
+ }
+
+ // Write as many aligned u32s as we can.
+ {
+ u32* cur_dst = reinterpret_cast<u32*>(aligned_start);
+ u32* const end_dst = reinterpret_cast<u32*>(aligned_end);
+
+ while (cur_dst < end_dst) {
+ *(cur_dst++) = this->GenerateRandomU32();
+ }
+ }
+
+ // Handle any leftover unaligned data.
+ if (aligned_end < end) {
+ const u32 rnd = this->GenerateRandomU32();
+ std::memcpy(reinterpret_cast<void*>(aligned_end), &rnd, end - aligned_end);
+ }
+ }
+
+ u32 GenerateRandomU32() {
+ // Advance state.
+ const u32 x0 =
+ (this->state.data[0] & TopBitmask) ^ this->state.data[1] ^ this->state.data[2];
+ const u32 y0 = this->state.data[3];
+ const u32 x1 = x0 ^ (x0 << 1);
+ const u32 y1 = y0 ^ (y0 >> 1) ^ x1;
+
+ const u32 state0 = this->state.data[1];
+ u32 state1 = this->state.data[2];
+ u32 state2 = x1 ^ (y1 << 10);
+ const u32 state3 = y1;
+
+ if ((y1 & 1) != 0) {
+ state1 ^= ParamMat1;
+ state2 ^= ParamMat2;
+ }
+
+ this->state.data[0] = state0;
+ this->state.data[1] = state1;
+ this->state.data[2] = state2;
+ this->state.data[3] = state3;
+
+ // Temper.
+ const u32 t1 = state0 + (state2 >> 8);
+ u32 t0 = state3 ^ t1;
+
+ if ((t1 & 1) != 0) {
+ t0 ^= ParamTmat;
+ }
+
+ return t0;
+ }
+
+ u64 GenerateRandomU64() {
+ const u32 lo = this->GenerateRandomU32();
+ const u32 hi = this->GenerateRandomU32();
+ return (u64{hi} << 32) | u64{lo};
+ }
+
+ float GenerateRandomF32() {
+ // Floats have 24 bits of mantissa.
+ constexpr u32 MantissaBits = 24;
+ return static_cast<float>(GenerateRandomU24()) * (1.0f / (1U << MantissaBits));
+ }
+
+ 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 u32 MantissaBits = 53;
+ constexpr u32 Shift1st = (64 - MantissaBits) / 2;
+ constexpr u32 Shift2nd = (64 - MantissaBits) - Shift1st;
+
+ const u32 first = (this->GenerateRandomU32() >> Shift1st);
+ const u32 second = (this->GenerateRandomU32() >> Shift2nd);
+
+ return (1.0 * first * (u64{1} << (32 - Shift2nd)) + second) *
+ (1.0 / (u64{1} << MantissaBits));
+ }
+};
+
+} // namespace Common
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