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CFileWatch

By , 1 Apr 2008
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Sample Image - FileWatch.jpg

Introduction

This class helps you to monitor files like in the DevStudio. If the file is modified outside your application, a message box pops up and lets you choose between ignoring modifications or reloading the data, thus discarding all changes.

If the file is modified, a message is sent either to the specified view or to the first view of a specified document. The message handler will call the reload function of the document class. The class should be thread safe.

Things you have to change in your View Class and Document Class:

In Your Document Class Header File

class CFileWatchAppDoc : public CRichEditDoc
{
    ....
public:
    void OnFileReload();
protected:
    DWORD m_hFileWatch;
    void AddToFileWatch();
};

In Your Document Class Source File

#include <span class="code-string">"FileWatch.h"</span>

CFileWatchAppDoc::CFileWatchAppDoc()
{
    m_hFileWatch = NULL;
}

CFileWatchAppDoc::~CFileWatchAppDoc()
{
    CFileWatch::RemoveHandle(m_hFileWatch);
}

BOOL CFileWatchAppDoc::OnSaveDocument(LPCTSTR lpszPathName)
{
    CFileWatch::RemoveHandle(m_hFileWatch);
    BOOL bSuccess = CRichEditDoc::OnSaveDocument(lpszPathName);
    AddToFileWatch();
   return bSuccess;
}

void CFileWatchAppDoc::SetPathName(LPCTSTR lpszPathName, BOOL bAddToMRU)
{
    CFileWatch::RemoveHandle(m_hFileWatch);
    CRichEditDoc::SetPathName(lpszPathName, bAddToMRU);
    AddToFileWatch();
}

void CFileWatchAppDoc::AddToFileWatch()
{
    m_hFileWatch =  CFileWatch::AddFileFolder(lpszPathName,
                                               NULL, this);
    CFileWatch::SetAutoReload(m_hFileWatch,
        &((CYourApp*)AfxGetApp())->m_bAutoReloadDocTypeXY);
}

void CFileWatchAppDoc::OnFileReload()
{
    // your reload code
    ...
    UpdateAllViews(NULL);
}

In Your View Class Header File

class CFileWatchAppView : public CRichEditView
{
    ...
protected:
    //{{AFX_MSG(CFileWatchAppView)
    afx_msg LRESULT OnFileWatchNotification(WPARAM wParam,
                                            LPARAM lParam);
    //}}AFX_MSG
    DECLARE_MESSAGE_MAP()
};

In Your View Class Source File

#include <span class="code-string">"FileWatch.h"</span>

BEGIN_MESSAGE_MAP(CFileWatchAppView, CRichEditView)
  //{{AFX_MSG_MAP(CFileWatchAppView)
  ON_REGISTERED_MESSAGE(CFileWatch::m_msgFileWatchNotify,
                        OnFileWatchNotification)
  //}}AFX_MSG_MAP
END_MESSAGE_MAP()

LRESULT CFileWatchAppView::OnFileWatchNotification(WPARAM wParam,
                                                   LPARAM lParam)
{
    CString sPathName = CString((LPCTSTR)lParam);
    DWORD hFileWatch = (DWORD)wParam;

    if (CFileWatch::Dialog(hFileWatch))
        GetDocument()->OnFileReload();

    return 0;
}

In Your Mainframe Class Source File

#include <span class="code-string">"FileWatch.h"</span>

void CMainFrame::OnClose()
{
    CFileWatch::Stop();

    CMDIFrameWnd::OnClose();
}

Add Non-document Files to the Watch

Non-document files, which should be monitored, can be added to the watch but must be associated with a view class. Use DWORD dwData or the file name to distinguish which file has been changed.

#include <span class="code-string">"FileWatch.h"</span>

void class::xy()
{
   ...
   DWORD hHandle = CFileWatch::AddFileFolder(LPCTSTR lpszFileName,
                HWND hWnd, CDocument* pDocument=NULL, DWORD dwData);
   ...
}

LRESULT CYourView::OnFileWatchNotification(WPARAM wParam,
                                                   LPARAM lParam)
{
    CString sPathName = CString((LPCTSTR)lParam);
    DWORD dwData = (DWORD)wParam;

    if (sPathName == GetDocument()->GetPathName())
      GetDocument()->OnFileReload();
    else
    ...

    return 0;
}

Note

Not all file systems record write time in the same manner. For example, on Windows NT FAT, create time has a resolution of 10 milliseconds, write time has a resolution of 2 seconds, and access time has a resolution of 1 day (really, the access date). On NTFS, access time has a resolution of 1 hour. Furthermore, FAT records times on disk in local time, while NTFS records times on disk in UTC, so it is not affected by changes in time zone or daylight saving time. I have no information about the resolution of the write time in FAT or FAT32. However, if the file is modified several times in the same time window, only one notification can be detected!

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

qweqwe
Software Developer (Senior)
Austria Austria
No Biography provided

Comments and Discussions

 
Generalsome wrong on 2tb disk Pinmembernhchmg15-Dec-10 22:50 
GeneralRecent article questions PinmemberVitali Halershtein9-Apr-08 0:45 
QuestionHow about files on a Windows network? PinmemberSharpmike24-Jan-05 4:33 
AnswerRe: How about files on a Windows network? PinmemberHQH7-Apr-08 20:02 
GeneralHelp Me Please PinmemberLOSTTWARE.com10-Nov-03 18:54 
QuestionHow we know which anothers application also are openning the file that our application is openning??? Pinmemberdoxuanhuyen9-Oct-03 17:11 
QuestionHow to monitor directory on Linux / UNIX without polling? PinmemberMark Fine9-May-03 4:25 
AnswerRe: How to monitor directory on Linux / UNIX without polling? PinmemberTheJosh2-Apr-08 13:11 
GeneralTop Code! Pinmemberigorss5-May-03 22:57 
Generalbug will happen Pinmemberhiro028-Dec-02 18:48 
QuestionHow to use CFileWatch in the dialog-based app? PinsussGolden Lee11-Sep-02 18:38 
General[Message Deleted] Pinmemberqweqwe15-Jun-01 8:01 
GeneralRe: DOWNLOAD LATEST VERSION HERE PinmemberAnthony_Yio13-Aug-02 1:44 

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