UnrealEngineUWP/Engine/Source/Developer/DerivedDataCache/Private/DDCCleanup.h

// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.

#pragma once

/** 
 * DDC Filesystem Cache cleanup thread.
 */
class FDDCCleanup : public FRunnable
{
	/** Singleton instance */
	static FDDCCleanup* Runnable;
	
	/** Thread to run the cleanup FRunnable on */
	FRunnableThread* Thread;
	/** > 0 if we've been asked to abort work in progress at the next opportunity */
	FThreadSafeCounter StopTaskCounter;
	/** List of filesystems to clean up */
	TArray< TSharedPtr< struct FFilesystemInfo > > CleanupList;
	/** Synchronization object */
	FCriticalSection DataLock;

	/** Constructor */
	FDDCCleanup();

	/** Destructor */
	virtual ~FDDCCleanup();

	// Begin FRunnable interface.
	virtual bool Init();
	virtual uint32 Run();
	virtual void Stop();
	virtual void Exit();
	// End FRunnable interface

	/** Checks if there's been any Stop requests */
	FORCEINLINE bool ShouldStop() const
	{
		return StopTaskCounter.GetValue() > 0;
	}

	/**
	 * Waits for a given amount of time periodically checking if there's been any Stop requests.
	 *
	 * @param InSeconds time in seconds to wait.
	 * @param InSleepTime interval at which to check for Stop requests.
	 */
	void Wait( const float InSeconds, const float InSleepTime = 0.1f );

	/**
	 * Performs directory cleanup.
	 *
	 * @param FilesystemInfo Filesystem to cleanup.
	 * @return true if the filesystem contained any directories to clean up, false otherwise.
	 */
	bool CleanupFilesystemDirectory( TSharedPtr< FFilesystemInfo > FilesystemInfo );

	/** Makes sure this thread has stopped properly */
	void EnsureCompletion();

public:

	/**
	 * Adds DDC filesystem to clean up.
	 *
	 * @param InCachePath Filesystem path.
	 * @param InDaysToDelete Number of days since last access time to consider a file as unused.
	 * @param InMaxContinuousFileChecks Number of files to check without pausing.
	 */
	void AddFilesystem( FString& InCachePath, int32 InDaysToDelete, int32 InMaxNumFoldersToCheck, int32 InMaxContinuousFileChecks );

	/** Gets DDC Cleanup singleton instance */
	static FDDCCleanup* Get();

	/** Shuts down DDC Cleanup thread. */
	static void Shutdown();
};