How to debug file change notifications obtained by FindFirstChangeNotification?

Question

So, the question is: I get some notifications I don't want to get. But I don't know for what file/dir I got them. Is there a way to know why given notification was fired?

If you think about ReadDirectoryChangesW, please include a meaningful code sample.

Answer 1

~pseudocode

HANDLE handles[MAX_HANDLES];
std::string dir_array[MAX_HANDLES];

for i from 0 to MAX_HANDLES:
   h[i] = FindFirstChangeNotification(dir_array[i]...);

nCount = MAX_HANDLES;
ret = WaitForMultipleObjects(handles, nCount ...);

// check if ret returns something between WAIT_OBJECT_0 and WAIT_OBJECT_0+nCount-1
if "so":
  ret -= WAIT_OBJECT_0;
  cout << "Directory " << dir_array[ret] << " changed" << endl;

See: http://msdn.microsoft.com/en-us/library/ms687025(VS.85).aspx

Answer 2

See on professional Win32 api newsgroup news://comp.os.ms-windows.programmer.win32 for well-known MS samples (C code) (since 90's...)

Answer 3

If you would like Windows to tell you what specific file or subdirectory changed, you will need to use ReadDirectoryChangesW. The asynchronous mode is fairly simple if you use a completion routine.

On the other hand, you will probably get better performance by using the slightly more complicated I/O completion ports approach. I would recommend downloading Wes Jones' excellent CDirectoryChangeWatcher source code as a starting point. There are several gotchas that his code will help you avoid, particularly in parsing the FILE_NOTIFY_INFORMATION records.