feat(numeric): add basic random number generator function

Redcraft.Utility/Source/Private/Numeric/Random.cpp

@@ -0,0 +1,51 @@
+#include "Numeric/Random.h"
+
+#include "Templates/Atomic.h"
+
+NAMESPACE_REDCRAFT_BEGIN
+NAMESPACE_MODULE_BEGIN(Redcraft)
+NAMESPACE_MODULE_BEGIN(Utility)
+
+NAMESPACE_BEGIN(Math)
+
+NAMESPACE_UNNAMED_BEGIN
+
+TAtomic<uint32> RandState = 586103306;
+
+NAMESPACE_UNNAMED_END
+
+uint32 Seed(uint32 InSeed)
+{
+	uint32 OldSeed = RandState.Load(EMemoryOrder::Relaxed);
+
+	if (InSeed != 0) RandState.Store(InSeed, EMemoryOrder::Relaxed);
+
+	return OldSeed;
+}
+
+uint32 Rand()
+{
+	uint32 Result;
+
+	RandState.FetchFn(
+		[&Result](uint32 Value)
+		{
+			Result = Value;
+
+			Result ^= Result << 13;
+			Result ^= Result >> 17;
+			Result ^= Result << 5;
+
+			return Result;
+		},
+		EMemoryOrder::Relaxed
+	);
+
+	return Result % 0x7FFFFFFF;
+}
+
+NAMESPACE_END(Math)
+
+NAMESPACE_MODULE_END(Utility)
+NAMESPACE_MODULE_END(Redcraft)
+NAMESPACE_REDCRAFT_END

Redcraft.Utility/Source/Public/Numeric/Numeric.h

@@ -6,3 +6,4 @@
 #include "Numeric/Numbers.h"
 #include "Numeric/Bit.h"
 #include "Numeric/Math.h"
+#include "Numeric/Random.h"

Redcraft.Utility/Source/Public/Numeric/Random.h

@@ -0,0 +1,88 @@
+#pragma once
+
+#include "CoreTypes.h"
+#include "Numeric/Bit.h"
+#include "Numeric/Math.h"
+
+NAMESPACE_REDCRAFT_BEGIN
+NAMESPACE_MODULE_BEGIN(Redcraft)
+NAMESPACE_MODULE_BEGIN(Utility)
+
+NAMESPACE_BEGIN(Math)
+
+/** Seeds the random number generator. Return the previous seed. */
+NODISCARD REDCRAFTUTILITY_API uint32 Seed(uint32 InSeed = 0);
+
+/** @return The generated random number within the range of [0, 0x7FFFFFFF). */
+NODISCARD REDCRAFTUTILITY_API uint32 Rand();
+
+/** @return The generated random number within the range of [0, A). */
+template <CIntegral T>
+NODISCARD FORCEINLINE T Rand(T A)
+{
+	constexpr uint32 RandStateNum = 0x7FFFFFFF;
+
+	if (A <= 0) return 0;
+
+	if (A <= RandStateNum) return Rand() % A;
+
+	constexpr uint32 BlockSize  = Math::BitFloor(RandStateNum);
+	constexpr uint   BlockWidth = Math::CountRightZero(BlockSize);
+
+	const T BlockNum = Math::DivAndCeil(A, BlockSize);
+
+	T Result = 0;
+
+	for (T I = 0; I < BlockNum; ++I)
+	{
+		Result ^= Rand();
+
+		Result <<= BlockWidth;
+	}
+
+	return Math::Abs(Result) % A;
+}
+
+/** @return The generated random number within the range of [0, A). */
+template <CFloatingPoint T>
+NODISCARD FORCEINLINE T Rand(T A)
+{
+	constexpr uint32 RandStateNum = 0x7FFFFFFF;
+
+	if (Math::IsNegative(A)) return TNumericLimits<T>::QuietNaN();
+
+	constexpr size_t BlockNum = Math::DivAndCeil(sizeof(T), 4);
+
+	T Multiplier = A;
+
+	Multiplier /= BlockNum;
+	Multiplier /= RandStateNum;
+
+	T Result = 0;
+
+	for (size_t I = 0; I < BlockNum; ++I)
+	{
+		Result += Rand() * Multiplier;
+	}
+
+	return Result;
+}
+
+/** @return The generated random number within the range of [A, B). */
+template <CArithmetic T, CArithmetic U> requires (CCommonType<T, U>)
+NODISCARD FORCEINLINE auto RandWithin(T A, U B)
+{
+	using FCommonT = TCommonType<T, U>;
+
+	if (A == B) return static_cast<FCommonT>(A);
+
+	if (A > B) return Math::RandWithin(B, A);
+
+	return static_cast<FCommonT>(A + Math::Rand(B - A));
+}
+
+NAMESPACE_END(Math)
+
+NAMESPACE_MODULE_END(Utility)
+NAMESPACE_MODULE_END(Redcraft)
+NAMESPACE_REDCRAFT_END