Directory Monitoring

From Forum Nokia Wiki

Reviewer Approved

This code is to monitor for file changes (added, erased) in a particular directory.

ID		Creation date	March 12, 2008
Platform	S60 3rd Edition S60 3rd Edition, FP1	Tested on devices	N73
Category	Symbian C++	Subcategory	File/Data

Keywords (APIs, classes, methods, functions):

Overview

This code shows how to monitor for file changes (added/erased) in a particular directory. There is also an application showing how to use the code Source Code

This snippet can be self-signed.

MMP file (optional)

The following capabilities and libraries are required:

CAPABILITY ReadUserData

Libraries needed

LIBRARY  euser.lib //RTimer, CActive

Header file

/*
 ============================================================================
 Name		: DirectoryMonitor.h
 Author	  : Olympio Cipriano
 Version	 : 1.0
 Copyright   : 
 Description : CDirectoryMonitor declaration
 ============================================================================
 */
 
#ifndef CDirectoryMonitor_H
#define CDirectoryMonitor_H
 
#include <e32base.h>	// For CActive, link against: euser.lib
#include <e32std.h>		// For RTimer, link against: euser.lib
#include <f32file.h>
 
enum TFileAction
	{
	EFileErased,
	EFileAdded
	};
 
class DirectoryObserver 
{
public:
      virtual void DirectoryChanged( const TDesC& aFileName, TFileAction aAction ) = 0;
};
 
class CDirectoryMonitor : public CActive
	{
public:
	// Cancel and destroy
	~CDirectoryMonitor();
 
	// Two-phased constructor.
	static CDirectoryMonitor* NewL( DirectoryObserver * iObserver );
 
	// Two-phased constructor.
	static CDirectoryMonitor* NewLC(DirectoryObserver * iObserver );
 
 
public:
 
	// New functions
	// Function for making the initial request
	void Monitor( const TDesC& aDirPath );
 
private:
	// C++ constructor
	CDirectoryMonitor( DirectoryObserver* aObserver );
 
	// Second-phase constructor
	void ConstructL();
 
	//directory internals
	void ListFiles( CDir*& aDir );
 
	void DiffDirectoryContents( );
 
	bool SearchEntry( const TEntry& aEntry, CDir* aDir );
 
	void Clean();
 
private:
	// From CActive
	// Handle completion
	void RunL();
 
	// How to cancel me
	void DoCancel();
 
	// Override to handle leaves from RunL(). Default implementation causes
	// the active scheduler to panic.
	TInt RunError(TInt aError);	
 
	struct TFileChange
	{
		TFileChange(const TEntry aEntry, TFileAction aAction)
		            :fileEntry(aEntry),action(aAction){}
		const TEntry fileEntry;
		TFileAction action;
	};
 
private:
	enum TCDirectoryMonitorState
		{
		EUninitialized, // Uninitialized
		EInitialized, // Initalized
		EError // Error condition
		};
 
private:
	TInt iState; // State of the active object
	RFs iFs;
	DirectoryObserver* iObserver;
	CDir* iOldDir;
	CDir* iNewDir;
	RArray<TFileChange> iFileChangeArray;
	RArray<TEntry> iFileList;
	HBufC* iPath;
	};
 
#endif // CDirectoryMonitor_H

Source file

/*
 ============================================================================
 Name		: DirectoryMonitor.cpp
 Author	  : Olympio Cipriano
 Version	 : 1.0
 Copyright   : 
 Description : CDirectoryMonitor implementation
 ============================================================================
 */
 
#include "DirectoryMonitor.h"
 
CDirectoryMonitor::CDirectoryMonitor( DirectoryObserver* aObserver ) :
	CActive(EPriorityStandard), 
	iObserver( aObserver )
	{
	}
 
CDirectoryMonitor* CDirectoryMonitor::NewLC( DirectoryObserver* aObserver )
	{
	CDirectoryMonitor* self = new ( ELeave ) CDirectoryMonitor( aObserver );
	CleanupStack::PushL(self);
	self->ConstructL();
	return self;
	}
 
CDirectoryMonitor* CDirectoryMonitor::NewL( DirectoryObserver* aObserver )
	{
	CDirectoryMonitor* self = CDirectoryMonitor::NewLC( aObserver );
	CleanupStack::Pop(); // self;
	return self;
	}
 
void CDirectoryMonitor::ConstructL()
	{
	User::LeaveIfError( iFs.Connect() );	
	CActiveScheduler::Add( this ); // Add to scheduler
	iPath = HBufC16::NewL(100);
	}
 
CDirectoryMonitor::~CDirectoryMonitor()
	{
	Cancel(); // Cancel any request, if outstanding
	iFs.Close();
	iFileChangeArray.Close();
	if( iOldDir )
		delete iOldDir;
	if( iNewDir )
		delete iNewDir;
	if( iPath )
		delete iPath;
	}
 
void CDirectoryMonitor::DoCancel()
	{
    iFs.NotifyChangeCancel( iStatus );
	}
 
void CDirectoryMonitor::Monitor( const TDesC& aDirPath )
	{
	*iPath = aDirPath;
	Cancel(); // Cancel any request, just to be sure
	iState = EUninitialized;
	iFs.NotifyChange( ENotifyFile, iStatus, *iPath );
	ListFiles( iOldDir );
	SetActive(); // Tell scheduler a request is active
	}
 
void CDirectoryMonitor::RunL()
{
	TInt err = iStatus.Int();  
	if ( err == KErrNone )
	{
		ListFiles( iNewDir );
		DiffDirectoryContents( );
		if( iObserver )
			for (int i = 0; i < iFileChangeArray.Count(); ++i)
			{
				TFileChange changeEntry = iFileChangeArray[i];			
				iObserver->DirectoryChanged( changeEntry.fileEntry.iName, changeEntry.action );
			}		
		Clean();
		iFs.NotifyChange( ENotifyEntry, iStatus, *iPath );
		SetActive(); // Tell scheduler a request is active 	
	}
}
 
TInt CDirectoryMonitor::RunError(TInt aError)
	{
	return aError;
	}
 
void CDirectoryMonitor::ListFiles( CDir*& aDir )
{
	if( aDir )
	{
		delete aDir;
		aDir = 0;
	}
	TInt err = iFs.GetDir( *iPath, KEntryAttNormal, ESortByName, aDir );
	if( err )
	{
	//TODO: error handling
	}
 
}
 
void CDirectoryMonitor::DiffDirectoryContents( )
{
	for (int i = 0; (iOldDir != NULL) && (i < iNewDir->Count()); ++i)
	{
		const TEntry entry = (const TEntry& )(*iNewDir)[i];
		if( ! SearchEntry( entry, iOldDir ) )
		{			
			//file added
			TFileChange change(entry,EFileAdded);
			iFileChangeArray.Append( change );
		}		
	}
	for (int i = 0; ( iOldDir != NULL ) && ( i < iOldDir->Count() ); ++i)
	{
		const TEntry entry = (const TEntry& )(*iOldDir)[i];
		if( ! SearchEntry( entry, iNewDir ) )
		{
			//file added
			TFileChange change(entry,EFileErased);
			iFileChangeArray.Append( change );
		}		
	}	
}
 
bool CDirectoryMonitor::SearchEntry( const TEntry& aEntry, CDir * aDir )
{	
	for (int i = 0; ( aDir != NULL ) && ( i < aDir->Count() ); ++i)
	{
		const TEntry& dirEntry = (const TEntry& ) (*aDir)[i];
		TDesC& entryName = (TDesC&) dirEntry.iName;
		if ( entryName.Compare( aEntry.iName ) == 0 )
			return true;				
	}
	return false;
}
 
void CDirectoryMonitor::Clean()
{
	if( iNewDir )
		{
		delete iNewDir;
		iNewDir = 0;
		}	
	iFileChangeArray.Reset();	
	ListFiles( iOldDir );
}
//end line

Postconditions

This code monitors a specific folder. A call to Monitor member funcion starts the monitoring process. The changes to be monitored are those occurred after the call to Monitor function.

Test application and other attachments

Directory Monitor Source Code: File:DirectoryMonitoring.zip

Community: Wiki