ScopeExit.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
namespace ScopeExitSupport
{
    /**
     * Not meant for direct consumption : use ON_SCOPE_EXIT instead.
     *
     * RAII class that calls a lambda when it is destroyed.
     */
    template <typename FuncType>
    class TScopeGuard
    {
        TScopeGuard(TScopeGuard&&) = delete;
        TScopeGuard(const TScopeGuard&) = delete;
        TScopeGuard& operator=(TScopeGuard&&) = delete;
        TScopeGuard& operator=(const TScopeGuard&) = delete;
 
    public:
        // Given a lambda, constructs an RAII scope guard.
        explicit TScopeGuard(FuncType&& InFunc)
            : Func((FuncType&&)InFunc)
        {
        }
 
        // Causes the lambda to be executed.
        ~TScopeGuard()
        {
            Func();
        }
 
    private:
        // The lambda to be executed when this guard goes out of scope.
        FuncType Func;
    };
 
    struct FScopeGuardSyntaxSupport
    {
        template <typename FuncType>
        TScopeGuard<FuncType> operator+(FuncType&& InFunc)
        {
            return TScopeGuard<FuncType>((FuncType&&)InFunc);
        }
    };
}
 
#define UE_PRIVATE_SCOPE_EXIT_JOIN(A, B) UE_PRIVATE_SCOPE_EXIT_JOIN_INNER(A, B)
#define UE_PRIVATE_SCOPE_EXIT_JOIN_INNER(A, B) A##B
 
 
 
/**
 * Enables a lambda to be executed on scope exit.
 *
 * Example:
 *    {
 *      FileHandle* Handle = GetFileHandle();
 *      ON_SCOPE_EXIT
 *      {
 *          CloseFile(Handle);
 *      };
 *
 *      DoSomethingWithFile( Handle );
 *
 *      // File will be closed automatically no matter how the scope is exited, e.g.:
 *      // * Any return statement.
 *      // * break or continue (if the scope is a loop body).
 *      // * An exception is thrown outside the block.
 *      // * Execution reaches the end of the block.
 *    }
 */
#define ON_SCOPE_EXIT const auto UE_PRIVATE_SCOPE_EXIT_JOIN(ScopeGuard_, __LINE__) = ::ScopeExitSupport::FScopeGuardSyntaxSupport() + [&]()