ScopeTryLock.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Misc/AssertionMacros.h"
#include "HAL/CriticalSection.h"
 
/**
 * Implements a scope lock using TryLock.
 *
 * This is a utility class that handles scope level locking using TryLock.
 * Scope locking helps to avoid programming errors by which a lock is acquired
 * and never released.
 *
 * <code>
 *  {
 *      // Try to acquire a lock on CriticalSection for the current scope.
 *      FScopeTryLock ScopeTryLock(CriticalSection);
 *      // Check that the lock was acquired.
 *      if (ScopeTryLock.IsLocked())
 *      {
 *          // If the lock was acquired, we can safely access resources protected
 *          // by the lock.
 *      }
 *      // When ScopeTryLock goes out of scope, the critical section will be
 *      // released if it was ever acquired.
 *  }
 * </code>
 */
class FScopeTryLock
{
public:
    // Constructor that tries to lock the critical section. Note that you must
    // call IsLocked to test that the lock was acquired.
    FScopeTryLock(FCriticalSection *InCriticalSection)
        : CriticalSection(InCriticalSection)
    {
        check(CriticalSection);
        if (!CriticalSection->TryLock())
        {
            CriticalSection = nullptr;
        }
    }
 
    // Destructor that will release the lock if it was ever acquired.
    ~FScopeTryLock()
    {
        if (CriticalSection)
        {
            CriticalSection->Unlock();
        }
    }
 
    FORCEINLINE bool IsLocked() const
    {
        return nullptr != CriticalSection;
    }
 
private:
    FScopeTryLock(FScopeTryLock const &InScopeLock) = delete;
    FScopeTryLock &operator=(FScopeTryLock &Rhs) = delete;
 
    FCriticalSection *CriticalSection;
};