feat(templates): add TScopeCallback TGuardValue and TScopeCounter

Redcraft.Utility/Source/Private/Testing/TemplatesTesting.cpp

@@ -24,6 +24,7 @@ void TestTemplates()
 	TestTuple();
 	TestFunction();
 	TestAtomic();
+	TestScopeHelper();
 	TestMiscTemplates();
 }
 
@@ -1381,6 +1382,93 @@ void TestAtomic()
 	}
 }
 
+void TestScopeHelper()
+{
+	{
+		int32 CheckNum = 0;
+		{
+			TScopeCallback ScopeCallback([&]() { CheckNum = 2; });
+			always_check(CheckNum == 0);
+			CheckNum = 1;
+			always_check(CheckNum == 1);
+		}
+		always_check(CheckNum == 2);
+	}
+
+	{
+		int32 CheckNum = 0;
+		{
+			TScopeCallback ScopeCallback([&]() { CheckNum = 2; });
+			always_check(CheckNum == 0);
+			CheckNum = 1;
+			always_check(CheckNum == 1);
+			ScopeCallback.Release();
+		}
+		always_check(CheckNum == 1);
+	}
+
+	{
+		int32 CheckNum = 0;
+		{
+			TScopeCallback ScopeCallbackA([&]() { CheckNum = 2; });
+			TScopeCallback ScopeCallbackB(MoveTemp(ScopeCallbackA));
+			always_check(CheckNum == 0);
+			CheckNum = 1;
+			always_check(CheckNum == 1);
+		}
+		always_check(CheckNum == 2);
+	}
+
+	{
+		int32 CheckNum = 1;
+		{
+			TGuardValue GuardValue(CheckNum);
+			CheckNum = 2;
+			always_check(CheckNum == 2);
+		}
+		always_check(CheckNum == 1);
+	}
+
+	{
+		int32 CheckNum = 1;
+		{
+			TGuardValue GuardValue(CheckNum, 2);
+			always_check(CheckNum == 2);
+		}
+		always_check(CheckNum == 1);
+	}
+
+	{
+		int32 CheckNum = 1;
+		{
+			TGuardValue GuardValue(CheckNum, 2);
+			always_check(CheckNum == 2);
+			GuardValue.Release();
+		}
+		always_check(CheckNum == 2);
+	}
+
+	{
+		int32 CheckNum = 1;
+		{
+			TGuardValue GuardValueA(CheckNum, 2);
+			TGuardValue GuardValueB(MoveTemp(GuardValueA));
+			always_check(CheckNum == 2);
+		}
+		always_check(CheckNum == 1);
+	}
+
+	{
+		int32 CheckNum = 1;
+		{
+			TScopeCounter GuardValue(CheckNum);
+			always_check(CheckNum == 2);
+		}
+		always_check(CheckNum == 1);
+	}
+
+}
+
 NAMESPACE_UNNAMED_BEGIN
 
 template <typename T>

Redcraft.Utility/Source/Public/Templates/ScopeHelper.h

@@ -0,0 +1,133 @@
+#pragma once
+
+#include "CoreTypes.h"
+#include "Templates/Utility.h"
+#include "TypeTraits/Invocable.h"
+#include "Templates/Noncopyable.h"
+#include "TypeTraits/CompositeType.h"
+#include "TypeTraits/Miscellaneous.h"
+#include "TypeTraits/SupportedOperations.h"
+
+NAMESPACE_REDCRAFT_BEGIN
+NAMESPACE_MODULE_BEGIN(Redcraft)
+NAMESPACE_MODULE_BEGIN(Utility)
+
+/** The class template is a general-purpose scope guard intended to call its callback function when a scope is exited. */
+template <CInvocable F> requires (CDestructible<F>)
+class TScopeCallback final : public FNoncopyable
+{
+public:
+
+	/** Initializes the callback function with a function or function object. */
+	template <typename InF> requires (!CSameAs<TRemoveCVRef<InF>, TScopeCallback> && CConstructibleFrom<F, InF>)
+	FORCEINLINE constexpr explicit TScopeCallback(InF&& Func) : Storage(Forward<InF>(Func)), bIsActive(true) { }
+
+	/** Move constructor. Initializes the stored object with the one in other.  */
+	FORCEINLINE constexpr TScopeCallback(TScopeCallback&& InValue) requires (CMoveConstructible<F>)
+		: Storage(MoveTemp(InValue.Storage)), bIsActive(InValue.bIsActive)
+	{
+		InValue.Release();
+	}
+
+	/** Calls the callback function if the TScopeCallback is active, then destroys the stored object. */
+	FORCEINLINE constexpr ~TScopeCallback()
+	{
+		if (bIsActive) Storage();
+	}
+
+	/** Makes the TScopeCallback inactive. */
+	FORCEINLINE constexpr void Release() { bIsActive = false; }
+
+	/** @return a const reference to the stored object. */
+	FORCEINLINE constexpr const F& Get() const { return Storage; }
+
+private:
+
+	F Storage;
+	bool bIsActive;
+
+};
+
+template <typename F>
+TScopeCallback(F) -> TScopeCallback<F>;
+
+/** The class template is a general-purpose scope guard intended to make sure a value is restored when a scope is exited. */
+template <typename T> requires (CCopyConstructible<T> && CCopyAssignable<T> && CMoveAssignable<T> && CDestructible<T>)
+class TGuardValue final : public FNoncopyable
+{
+public:
+
+	/** Initializes the TGuardValue with a reference. */
+	FORCEINLINE constexpr TGuardValue(T& InReference) : Reference(InReference), OldValue(InReference), bIsActive(true) { }
+
+	/** Initializes the TGuardValue with a reference and assign a new value to the reference. */
+	template <typename U> requires (CAssignableFrom<T&, U>)
+	FORCEINLINE constexpr TGuardValue(T& InReference, U&& InValue) : Reference(InReference), OldValue(InReference), bIsActive(true) { InReference = InValue; }
+
+	/** Move constructor. Initializes the referenced value and old value with the one in other.  */
+	FORCEINLINE constexpr TGuardValue(TGuardValue&& InValue) requires (CMoveConstructible<T>)
+		: Reference(InValue.Reference), OldValue(MoveTemp(InValue.OldValue)), bIsActive(InValue.bIsActive)
+	{
+		InValue.Release();
+	}
+
+	/** Restore the referenced value if the TGuardValue is active, then destroys the old value. */
+	FORCEINLINE constexpr ~TGuardValue()
+	{
+		if (bIsActive) Reference = MoveTemp(OldValue);
+	}
+
+	/** Makes the TGuardValue inactive. */
+	FORCEINLINE constexpr void Release() { bIsActive = false; }
+
+	/** @return a const reference to the old value. */
+	FORCEINLINE constexpr const T& Get() const { return OldValue; }
+
+private:
+
+	T& Reference;
+	T OldValue;
+	bool bIsActive;
+
+};
+
+template <typename T>
+TGuardValue(T&) -> TGuardValue<T>;
+
+template <typename T, typename U>
+TGuardValue(T&, U&&) -> TGuardValue<T>;
+
+/** Commonly used to make sure a value is incremented, and then decremented when a scope is exited. */
+template <typename T> requires (requires(T& Value) { ++Value; --Value; })
+class TScopeCounter : public FNoncopyable
+{
+public:
+
+	/** Initializes the TScopeCounter with a reference and increments it. */
+	FORCEINLINE constexpr TScopeCounter(T& InReference)
+		: Reference(InReference)
+	{
+		++Reference;
+	}
+
+	/** Decrements the referenced value. */
+	FORCEINLINE constexpr ~TScopeCounter()
+	{
+		--Reference;
+	}
+
+	/** @return a const reference to the value. */
+	FORCEINLINE constexpr const T& Get() const { return Reference; }
+
+private:
+
+	T& Reference;
+
+};
+
+template <typename T>
+TScopeCounter(T&) -> TScopeCounter<T>;
+
+NAMESPACE_MODULE_END(Utility)
+NAMESPACE_MODULE_END(Redcraft)
+NAMESPACE_REDCRAFT_END

Redcraft.Utility/Source/Public/Templates/Templates.h

@@ -14,3 +14,4 @@
 #include "Templates/TypeHash.h"
 #include "Templates/Function.h"
 #include "Templates/Atomic.h"
+#include "Templates/ScopeHelper.h"

Redcraft.Utility/Source/Public/Testing/TemplatesTesting.h

@@ -17,6 +17,7 @@ REDCRAFTUTILITY_API void TestAny();
 REDCRAFTUTILITY_API void TestTuple();
 REDCRAFTUTILITY_API void TestFunction();
 REDCRAFTUTILITY_API void TestAtomic();
+REDCRAFTUTILITY_API void TestScopeHelper();
 REDCRAFTUTILITY_API void TestMiscTemplates();
 
 NAMESPACE_END(Testing)