Obtaining Directory Change Notifications

迷南。 2021-10-18 12:00 169阅读 0赞

**Obtaining Directory Change Notifications**

** **

About APIs, you can go to this link: [http://msdn.microsoft.com/en-us/library/aa365261(VS.85).aspx][http_msdn.microsoft.com_en-us_library_aa365261_VS.85_.aspx]

Note following items extracted from MSDN:

1.     The [wait functions][] can monitor the specified directory or subtree by using the handle returned by the **FindFirstChangeNotification** function. A wait is satisfied when one of the filter conditions occurs in the monitored directory or subtree.

2.     After the wait has been satisfied, the application can respond to this condition and continue monitoring the directory by calling the [**FindNextChangeNotification**][FindNextChangeNotification] function and the appropriate wait function. When the handle is no longer needed, it can be closed by using the [**FindCloseChangeNotification**][FindCloseChangeNotification] function.

3.     This function does not indicate the change that satisfied the wait condition. To retrieve information about the specific change as part of the notification, use the [**ReadDirectoryChangesW**][ReadDirectoryChangesW] function.

To read the changes, we can use a WIN32\_FIND\_DATA list to keep the old attributes of the directory.

1.       Adding the specified folder to monitor queue

<table style="border-right:medium none;border-top:medium none;border-left:medium none;border-bottom:medium none;border-collapse:collapse;"> 
 <tbody> 
 <tr> 
 <td style="border-right:#000000 1pt solid;border-top:#000000 1pt solid;border-left:#000000 1pt solid;width:6.65in;border-bottom:#000000 1pt solid;"> void CFileMonitor::Add(const _bstr_t &amp;file) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CFileMonitor *pThis = new CFileMonitor(file); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //Reading files in the directory &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pThis-&gt;RefreshDirectory(FALSE); &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pThis-&gt;SetChange(::FindFirstChangeNotification( &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; path, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; FALSE,&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;FILE_NOTIFY_CHANGE_FILE_NAME | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;FILE_NOTIFY_CHANGE_LAST_WRITE &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; )); &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (pThis-&gt;GetChange() == INVALID_HANDLE_VALUE) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; delete pThis; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; DWORD ThreadId; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; HANDLE ht = ::CreateThread( &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; NULL, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp; CFileMonitor::ThreadAdd, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pThis,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &amp;ThreadId);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (ht == NULL) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; delete pThis; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; else &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ::CloseHandle(ht); } &nbsp; &nbsp; &nbsp;</td> 
 </tr> 
 </tbody> 
</table>

2.       In thread Add, wait and capture the change notification

3.       Compare the items

<table style="border-right:medium none;border-top:medium none;border-left:medium none;border-bottom:medium none;border-collapse:collapse;"> 
 <tbody> 
 <tr> 
 <td style="border-right:#000000 1pt solid;border-top:#000000 1pt solid;border-left:#000000 1pt solid;width:6.65in;border-bottom:#000000 1pt solid;"> void CFileMonitor::RefreshDirectory(BOOL bNotify /* default is TRUE */) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (m_path.length() == 0) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; // find all the files that match the path spec &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; int count = 0; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; WIN32_FIND_DATA *pFindArray = NULL; &nbsp;&nbsp; &nbsp;&nbsp; WIN32_FIND_DATA FindFileData; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; HANDLE hFind = ::FindFirstFile(m_path, &amp;FindFileData); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; BOOL more = hFind != INVALID_HANDLE_VALUE; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; while(more) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if ((FindFileData.dwFileAttributes &amp; FILE_ATTRIBUTE_DIRECTORY) == 0) // skip directories &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; // allocate a new entry in this snap shot (pFinDArray) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; count++; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pFindArray = (WIN32_FIND_DATA *)realloc(pFindArray, count * sizeof(*pFindArray)); &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; // add this file to the new snap shot &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; memcpy(pFindArray + count - 1, &amp;FindFileData, sizeof(*pFindArray)); &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (bNotify) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; DWORD fcs = GetFileStatus(m_pFindArray, m_count, FindFileData); &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (fcs != FILE_CHANGE_NONE) &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; OnFileChange(FindFileData, fcs); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; more = ::FindNextFile(hFind, &amp;FindFileData); &nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (m_pFindArray) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; free(m_pFindArray); &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; m_pFindArray = pFindArray; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; m_count = count; } &nbsp;</td> 
 </tr> 
 </tbody> 
</table>

转载于:https://www.cnblogs.com/pangpangxiong/archive/2009/09/08/1562630.html

[http_msdn.microsoft.com_en-us_library_aa365261_VS.85_.aspx]: http://msdn.microsoft.com/en-us/library/aa365261%28VS.85%29.aspx
[wait functions]: http://msdn.microsoft.com/en-us/library/ms687069%28VS.85%29.aspx
[FindNextChangeNotification]: http://msdn.microsoft.com/en-us/library/aa364427%28VS.85%29.aspx
[FindCloseChangeNotification]: http://msdn.microsoft.com/en-us/library/aa364414%28VS.85%29.aspx
[ReadDirectoryChangesW]: http://msdn.microsoft.com/en-us/library/aa365465%28VS.85%29.aspx