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Posted 31 Jan 2001

CDirectoryChangeWatcher - ReadDirectoryChangesW all wrapped up

, 11 May 2002
This class wraps up ReadDirectoryChangesW.
// DirectoryChanges.h: interface for the 
// CDirectoryChangeWatcher and CDirectoryChangeHandler classes.
//  Uses an io completion port and ReadDirectoryChangesW -- this code will only work on 
//	Windows NT/2000/XP.
//	The directory being watched must be a directory on a Windows NT/2000/XP machine
//	These classes are based on the FWatch sample program in the SDK.
//	If you get a compile time error that ReadDirectoryChangesW is an undeclared identifier,
//  you'll need to #define _WIN32_WINNT 0x400 in stdafx.h.
//	Copyright 2001. Wes Jones (
//	This code is free for use under the following conditions:
//		You may not claim authorship of this code.
//		You may not sell or distrubute this code without author's permission.
//		You are not permitted to sell this code in it's compiled, non-compiled, executable, or any other form. 
//		Executable code excepted in the case that it is not sold separately from an application which 
//		uses this it. This means you can use this code for your applications as you see fit, but this code may not be sold in any form
//		to others for use in their applications.
//		This copyright notice may not be removed.
//		If this code was NOT obtained by downloading it from,
//		or given to you by a friend or coworker, please tell me, & let me know how you got it. There a plenty of lazy bastards that 
//		collect source code from the internet, and then sell it as part of 
//		a 'Programmer's Library'.  Using this code for such a purpose is stricly prohibited.
//		If you'd like to pay me to turn this into an ActiveX/COM object so you 
//		can use it in a Visual Basic application, feel free to contact me with an offer,
//		and I will create it for you. Otherwise, here is the source code, and you may make your own
//		ActiveX/COM object, providing that it is not sold separately.
//  No guarantees or warranties are expressed or implied. 
//	This code may contain bugs.
//	Warning: May contain matter. If this should come into contact with anti-matter, a violent explosion may occur.

//  Please let me know of any bugs, bug fixes, or enhancements made to this code.
//  If you have ideas for this, and/or tips or admonitions, I would be glad to hear them.
//	See notes at top of DirectoryChanges.cpp modification history and more info.

#if !defined(AFX_DIRECTORYCHANGES_H__02E53FDE_CB22_4176_B6D7_DA3675D9F1A6__INCLUDED_)

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#include <afxmt.h>
#include <afxtempl.h>


class CFileNotifyInformation;//helper class 
class CDirectoryChangeWatcher;
class CDelayedDirectoryChangeHandler;//helper class...used in implementation

class CDirectoryChangeHandler
 A class to handle changes to files in a directory.  
 The virtual On_Filexxx() functions are called whenever changes are made to a watched directory that is being handled by this object...
 The On_Filexxx() functions execute in the context of the main thread if true is passed to the constructor of CDirectoryChangeWatcher,
 OR they fire in the context of a worker thread if false is passed to the constructor of CDirectoryChangeWatcher

		A CDirectoryChangeHandler can only be used by ONE CDirectoryChangeWatcher object,
		but a CDirectoryChangeWatcher object may use multiple CDirectoryChangeHandler objects.

	When this object is destroyed, whatever directories that it was being used to handle directory changes for
	will automatically be 'unwatched'.

	The class is reference counted.  The reference count is increased every time it is used 
	in a (successfull) call to CDirectoryChangeWatcher::WatchDirectory() and is decremented whenever
	the directory becomes 'unwatched'.

   The only notifications are File Added, Removed, Modified, and Renamed.
   Even though the CDirectoryChangeWatcher::WatchDirectory (which'll call ReadDirectoryChangesW()) function allows you to specify flags 
   to watch for changes to last access time, last write time, attributes changed, etc,
   these changes all map out to On_FileModified() which doesn't specify the type of modification.

  NOTE:   The CDirectoryChangeHandler::On_Filexxx() functions
		  are called in the context of the main thread, the thread that called CDirectoryChangeWatcher::WatchDirectory(),
		  if you pass true to the constructor of CDirectoryChangeWatcher. This is accomplished via a hidden window,
		  and REQUIRES that your app has a message pump. 
		  For console applications, or applications w/out a message pump, you can pass false to the constructor
		  of CDirectoryChangeWatcher, and these notifications will fire in the context of a worker thread.  By passing false
		  to the constructor of CDirectoryChangeWatcher, you do NOT NEED a message pump in your application.


	virtual ~CDirectoryChangeHandler();

	//this class is reference counted
	long AddRef();
	long Release();
	long CurRefCnt()const;

	BOOL UnwatchDirectory();//causes CDirectoryChangeWatcher::UnwatchDirectory() to be called.
	const CString & GetChangedDirectoryName() const { return m_strChangedDirectoryName;}//WARNING: don't use this, this function will be removed in a future release.
								//returns the directory name where the change occured.  This contains
							   //the last directory to have changed if the same CDirectoryChangeHandler is
							   //being used to watch multiple directories. It will return an empty string
							   //if no changes have been made to a directory yet.   It will always be the 
							   //name of the currently changed directory(as specified in CDirectoryChangeWatcher::WatchDirectory())
							   //if called in the context of one of the
							   //On_Filexxx() functions.
	//	Override these functions:
	//	These functions are called when the directory to watch has had a change made to it
	virtual void On_FileAdded(const CString & strFileName); //=0;
			//	On_FileAdded()
			//	This function is called when a file in one of the watched folders(or subfolders)
			//	has been created.
			//	For this function to execute you'll need to specify FILE_NOTIFY_CHANGE_FILE_NAME or FILE_NOTIFY_CHANGE_DIR_NAME(for directories)
			//  when you call CDirectoryChangeWatcher::WatchDirectory()
	virtual void On_FileRemoved(const CString & strFileName);// = 0;
			//	On_FileRemoved()
			//	This function is called when a file in one of the watched folders(or subfolders)
			//	has been deleted(or moved to another directory)
			//	For this function to execute you'll need to specify FILE_NOTIFY_CHANGE_FILE_NAME or FILE_NOTIFY_CHANGE_DIR_NAME(for directories)
			//  when you call CDirectoryChangeWatcher::WatchDirecotry()

	virtual void On_FileNameChanged(const CString & strOldFileName, const CString & strNewFileName);// = 0;
			//	On_FileNameChanged()
			//	This function is called when a file in one of the watched folders(or subfolders)
			//	has been renamed.
			//	You'll need to specify FILE_NOTIFY_CHANGE_FILE_NAME (or FILE_NOTIFY_CHANGE_DIR_NAME(for directories))
			//	when you call CDirectoryChangeWatcher::WatchDirectory()

	virtual void On_FileModified(const CString & strFileName);// = 0;
			//	On_FileModified()
			//	This function is called whenever an attribute specified by the watch
			//	filter has changed on a file in the watched directory or 
			//	Specify any of the following flags when you call CDirectoryChangeWatcher::WatchDirectory()
			//	FILE_NOTIFY_CHANGE_CREATION (* See Note # 1* )
			//	General Note)  Windows tries to optimize some of these notifications.  You may not get 
			//				   a notification every single time a file is accessed for example.  
			//				   There's a MS KB article or something on this(sorry forgot which one).
			//	Note #1	)   This notification isn't what you might think(FILE_NOTIFY_CHANGE_CREATION). 
			//				See the help files for ReadDirectoryChangesW...
			//				This notifies you of a change to the file's 
			//				creation time, not when the file is created.  
			//				Use FILE_NOTIFY_CHANGE_FILE_NAME to know about newly created files.

	virtual void On_ReadDirectoryChangesError(DWORD dwError, const CString & strDirectoryName);
			//	On_ReadDirectoryChangesError()
			//	This function is called when ReadDirectoryChangesW() fails during normal
			//	operation (ie: some time after you've called CDirectoryChangeWatcher::WatchDirectory())
			//	NOTE:  *** READ THIS *** READ THIS *** READ THIS *** READ THIS ***
			//	NOTE: If this function has been called, the watched directory has been automatically unwatched.
			//			You will not receive any further notifications for that directory until 
			//			you call CDirectoryChangeWatcher::WatchDirectory() again.
			//	On_WatchStopped() will not be called.

	virtual void On_WatchStarted(DWORD dwError, const CString & strDirectoryName);
			//	void On_WatchStarted()
			//	This function is called when a directory watch has begun.  
			//	It will be called whether CDirectoryChangeWatcher::WatchDirectory() is successful or not. Check the dwError parameter.
			//	DWORD dwError					 -- 0 if successful, else it's the return value of GetLastError() 
			//										indicating why the watch failed.
			//	const CString & strDirectoryName -- The full path and name of the directory being watched.
	virtual void On_WatchStopped(const CString & strDirectoryName);
			//	void On_WatchStopped()
			//	This function is called when a directory is unwatched (except on the case of the direcotry being unwatched due to an error)
			//	This function MAY be called before the destructor of CDirectoryChangeWatcher 
			//	finishes.  
			//	Be careful if your implementation of this fuction
			//	interacts with some sort of a window handle or other object(a class, a file, etc.).  
			//	It's possible that that object/window handle will NOT be valid anymore the very last time
			//	that On_WatchStopped() is called.  
			//	This scenario is likely if the CDirectoryChangeWatcher instance is currently watching a
			//	directory, and it's destructor is called some time AFTER these objects/windows
			//	your change handler interacts with have been destroyed.
			//	If your CDirectoryChangeHandler derived class interacts w/ a window or other
			//	object, it's a good idea to unwatch any directories before the object/window is destroyed.
			//	Otherwise, place tests for valid objects/windows in the implementation of this function.
			//  Failure to follow either tip can result in a mysterious RTFM error, or a 'Run time errors'

	virtual bool On_FilterNotification(DWORD dwNotifyAction, LPCTSTR szFileName, LPCTSTR szNewFileName);
			//	bool On_FilterNotification(DWORD dwNotifyAction, LPCTSTR szFileName, LPCTSTR szNewFileName);
			//	This function gives your class a chance to filter unwanted notifications.
			//			DWORD	dwNotifyAction	-- specifies the event to filter
			//			LPCTSTR szFileName		-- specifies the name of the file for the event.
			//			LPCTSTR szNewFileName	-- specifies the new file name of a file that has been renamed.
			//			**	szFileName and szNewFileName will always be the full path and file name with extention.
			//			return true , and you will receive the notification.
			//			return false, and your class will NOT receive the notification.
			//	Valid values of dwNotifyAction:
			//		FILE_ACTION_ADDED			-- On_FileAdded() is about to be called.
			//		FILE_ACTION_REMOVED			-- On_FileRemoved() is about to be called.
			//		FILE_ACTION_MODIFIED		-- On_FileModified() is about to be called.
			//		FILE_ACTION_RENAMED_OLD_NAME-- On_FileNameChanged() is about to be call.
			//	NOTE:  When the value of dwNotifyAction is FILE_ACTION_RENAMED_OLD_NAME,
			//			szFileName will be the old name of the file, and szNewFileName will
			//			be the new name of the renamed file.
			//  The default implementation always returns true, indicating that all notifications will 
			//	be sent.
			//	NOTE:	This function may or may not be called depending upon the flags you specify to control
			//			filter behavior.
			//			If you are specifying filters when watching the directory, you will not get this notification
			//			if the file name does not pass the filter test, even if this function returns true.
	//	End Override these functions (ie: don't worry about the rest of this class)
	void SetChangedDirectoryName(const CString & strChangedDirName);//please don't use this function, it will be removed in future releases.
	long m_nRefCnt;
	CString m_strChangedDirectoryName;//will be removed in a future release.

	friend class CDirectoryChangeWatcher;
	friend class CDelayedDirectoryChangeHandler;
	//	This class keeps a reference to the CDirectoryChangeHandler 
	//	that was used when an object of this type is passed 
	//	to CDirectoryChangeWatcher::WatchDirectory().
	//	This way, when the CDirectoryChangeWatcher object is destroyed(or if CDirectoryChangeHandler::UnwatchDirectory() is called)
	//	AFTER CDirectoryChangeWatcher::UnwatchDirecotry() or CDirectoryChangeWatcher::UnwatchAllDirectories() is called 
	//	the directory(or direcotries) that this 
	//	CDirectoryChangeWatcher object is handling will be automatically unwatched
	//	If the CDirectoryChangeWatcher object is destroyed before the CDirectoryChangeHandler objects 
	//	that are being used with that watcher are destroyed, the reference counting prevents
	//	this class from referencing a destructed object.
	//	Basically, neither class needs to worry about the lifetime of the other(CDirectoryChangeWatcher && CDirectoryChangeHandler)

	long  ReferencesWatcher(CDirectoryChangeWatcher * pDirChangeWatcher);
	long  ReleaseReferenceToWatcher(CDirectoryChangeWatcher * pDirChangeWatcher);
	CDirectoryChangeWatcher * m_pDirChangeWatcher;
	long   m_nWatcherRefCnt; //<-- when this reaches 0, m_pDirChangeWatcher is set to NULL
	CCriticalSection m_csWatcher;


class CDirectoryChangeWatcher  
	A class to monitor a directory for changes made to files in it, or it's subfolders.
	The class CDirectoryChangeHandler handles the changes. You derive a class from CDirectoryChangeHandler to handle them.

	This class uses the Win32 API ReadDirectoryChangesW() to watch a directory for file changes.

	Multiple directories can be watched simultaneously using a single instance of CDirectoryChangeWatcher.
	Single or multiple instances of CDirectoryChangeHandler object(s) can be used to handle changes to watched directories.
	Directories can be added and removed from the watch dynamically at run time without destroying 
	the CDirectoryChangeWatcher object (or CDirectoryChangeHandler object(s).

	This class uses a worker thread, an io completion port, and ReadDirectoryChangesW() to monitor changes to a direcory (or subdirectories).
	There will always only be a single thread no matter how many directories are being watched(per instance of CDirectoryChangeHandler)

    This class uses worker threads.
	Notifications (calling CDirectoryChangeHandler's virtual functions) are executed 
	in the context of either the main thread, OR in a worker thread.

	The 'main' thread is the thread that first calls CDirectoryChangeWatcher::WatchDirectory().
	For notifications to execute in the main thread, it's required that the calling thread(usually the main thread) 
	has a message pump in order to process the notifications.

	For applications w/out a message pump, notifications are executed in the context of a worker thread.

	See the constructor for CDirectoryChangeWatcher.


	enum	{  //options for determining the behavior of the filter tests.
			   FILTERS_DONT_USE_FILTERS		= 1, //never test the include/exclude filters. CDirectoryChangeHandler::On_FilterNotification() is still called.
			   FILTERS_CHECK_FULL_PATH		= 2, //For the file path: "C:\FolderName\SubFolder\", the entire path is checked for the filter pattern.
			   FILTERS_CHECK_PARTIAL_PATH	= 4, //For the file path: "C:\FolderName\SubFolder\", only "SubFolder\" is checked against the filter pattern, provided that you are watching the folder "C:\FolderName", and you are also watching subfolders.
			   FILTERS_CHECK_FILE_NAME_ONLY	= 8, //For the file path: "C:\FolderName\SubFolder\", only "" is checked against the filter pattern.
			   FILTERS_TEST_HANDLER_FIRST	= 16, //test CDirectoryChangeHandler::On_FilterNotification() before checking the include/exclude filters. the default is to check the include/exclude filters first.
			   FILTERS_DONT_USE_HANDLER_FILTER = 32, //CDirectoryChangeHander::On_FilterNotification() won't be called.
			   FILTERS_NO_WATCHSTART_NOTIFICATION = 64,//CDirectoryChangeHander::On_WatchStarted() won't be called.
			   FILTERS_NO_WATCHSTOP_NOTIFICATION  = 128,//CDirectoryChangeHander::On_WatchStopped() won't be called.

	CDirectoryChangeWatcher(bool bAppHasGUI = true, DWORD dwFilterFlags = FILTERS_DEFAULT_BEHAVIOR);//see comments in ctor .cpp file.
	virtual ~CDirectoryChangeWatcher();

	//	Starts a watch on a directory:
	DWORD	WatchDirectory(const CString & strDirToWatch, 
						   DWORD dwChangesToWatchFor, 
						   CDirectoryChangeHandler * pChangeHandler, 
						   BOOL bWatchSubDirs = FALSE,
						   LPCTSTR szIncludeFilter = NULL,
						   LPCTSTR szExcludeFilter = NULL);

	BOOL	IsWatchingDirectory (const CString & strDirName)const;
	int		NumWatchedDirectories()const; //counts # of directories being watched.

	BOOL	UnwatchDirectory(const CString & strDirToStopWatching);//stops watching specified directory.
	BOOL	UnwatchAllDirectories();//stops watching ALL watched directories.

	DWORD	SetFilterFlags(DWORD dwFilterFlags);//sets filter behavior for directories watched AFTER this function has been called.
	DWORD	GetFilterFlags()const{return m_dwFilterFlags;}

	virtual void On_ThreadInitialize(){}//All file change notifications has taken place in the context of a worker any thread initialization here..
	virtual void On_ThreadExit(){}//do thread cleanup here
	friend class CDirectoryChangeHandler;
	BOOL UnwatchDirectory(CDirectoryChangeHandler * pChangeHandler);//called in CDirectoryChangeHandler::~CDirectoryChangeHandler()

	UINT static MonitorDirectoryChanges(LPVOID lpvThis );//the worker thread that monitors directories.
	class CDirWatchInfo 
		//this class is used internally by CDirectoryChangeWatcher
		//to help manage the watched directories
		CDirWatchInfo();		//private & not implemented
		CDirWatchInfo & operator=(const CDirWatchInfo & rhs);//so that they're aren't accidentally used. -- you'll get a linker error
		CDirWatchInfo(HANDLE hDir, const CString & strDirectoryName, 
					  CDirectoryChangeHandler * pChangeHandler, 
					  DWORD dwChangeFilter, BOOL bWatchSubDir, 
					  bool bAppHasGUI,
					  LPCTSTR szIncludeFilter,
					  LPCTSTR szExcludeFilter,
					  DWORD dwFilterFlags);
		~CDirWatchInfo( );//only I can delete myself....use DeleteSelf()
		void DeleteSelf(CDirectoryChangeWatcher * pWatcher);
		DWORD StartMonitor(HANDLE hCompPort);
		BOOL UnwatchDirectory( HANDLE hCompPort );
		BOOL SignalShutdown( HANDLE hCompPort );
		BOOL WaitForShutdown();			   
		BOOL LockProperties() { return m_cs.Lock(); }
		BOOL UnlockProperties(){ return m_cs.Unlock();	}

		CDelayedDirectoryChangeHandler* GetChangeHandler() const;
		CDirectoryChangeHandler * GetRealChangeHandler() const;//the 'real' change handler is your CDirectoryChangeHandler derived class.
		CDirectoryChangeHandler * SetRealDirectoryChangeHandler(CDirectoryChangeHandler * pChangeHandler);
		BOOL CloseDirectoryHandle();
		//CDirectoryChangeHandler * m_pChangeHandler;
		CDelayedDirectoryChangeHandler * m_pChangeHandler;
		HANDLE      m_hDir;//handle to directory that we're watching
		DWORD		m_dwChangeFilter;
		BOOL		m_bWatchSubDir;
		CString     m_strDirName;//name of the directory that we're watching
		CHAR        m_Buffer[ READ_DIR_CHANGE_BUFFER_SIZE ];//buffer for ReadDirectoryChangesW
		DWORD       m_dwBufLength;//length or returned data from ReadDirectoryChangesW -- ignored?...
		OVERLAPPED  m_Overlapped;
		DWORD		m_dwReadDirError;//indicates the success of the call to ReadDirectoryChanges()
		CCriticalSection m_cs;
		CEvent		m_StartStopEvent;
		enum eRunningState{
		eRunningState m_RunningState;
		};//end nested class CDirWatchInfo 

	void ProcessChangeNotifications(IN CFileNotifyInformation & notify_info, 
									IN CDirWatchInfo * pdi,
									OUT DWORD & ref_dwReadBuffer_Offset);
	friend class CDirWatchInfo;//so that CDirWatchInfo can call the following function.
	long ReleaseReferenceToWatcher(CDirectoryChangeHandler * pChangeHandler);

	BOOL	UnwatchDirectoryBecauseOfError(CDirWatchInfo * pWatchInfo);//called in case of error.
	int		AddToWatchInfo(CDirWatchInfo * pWatchInfo);
	//	functions for retrieving the directory watch info based on different parameters
	CDirWatchInfo *	GetDirWatchInfo(IN const CString & strDirName, OUT int & ref_nIdx)const;
	CDirWatchInfo *	GetDirWatchInfo(IN CDirWatchInfo * pWatchInfo, OUT int & ref_nIdx)const;
	CDirWatchInfo * GetDirWatchInfo(IN CDirectoryChangeHandler * pChangeHandler, OUT int & ref_nIdx)const;

	HANDLE m_hCompPort;	//i/o completion port
	HANDLE m_hThread;	//MonitorDirectoryChanges() thread handle
	DWORD  m_dwThreadID;
	CTypedPtrArray<CPtrArray, CDirWatchInfo*> m_DirectoriesToWatch; //holds info about the directories that we're watching.
	CCriticalSection m_csDirWatchInfo;

	bool	m_bAppHasGUI; //dispatch to main thread, or a worker thread?
	DWORD	m_dwFilterFlags;//options for determining the behavior of the filter tests.

#endif // !defined(AFX_DIRECTORYCHANGES_H__02E53FDE_CB22_4176_B6D7_DA3675D9F1A6__INCLUDED_)

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About the Author

Wes Jones
Web Developer
United States United States
No Biography provided

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