FILE_NOTIFY_CHANGE_SIZE and FindFirstChangeNotification behavior in W7 and XP

[C++ Programming]

Hello,

I'm using a small program that notify me when a file size change inside a directory. The program worked perfect under Win XP, now in Windows 7 the size changes are ignored for long periods and notifications are not in sync with the changes.

At first glance that could be seen as something related to caching/flushing differences between XP and Win 7 but I verified that the file I'm monitoring is being flushed to the disk and is not staying in cache.

I used the command tail -f monitoredfile.txt displaying the file content as it is updated and I was able to see all the changes in real time but my monitor program wasn't reporting any file size change.

This is the monitor program:

#include
#include
#include
#include

void *******Directory(LPTSTR);
void *******Tree(LPTSTR);
void WatchDirectory(LPTSTR);

int _tmain(int argc, TCHAR *argv[])
{
if(argc != 2)
{
_tprintf(TEXT("Usage: %s \n"), argv[0]);
return 1;
}

WatchDirectory(argv[1]);
}

void WatchDirectory(LPTSTR lpDir)
{
DWORD dwWaitStatus;
HANDLE dwChangeHandles[2];
TCHAR lpDrive[4];
TCHAR lpFile[_MAX_FNAME];
TCHAR lpExt[_MAX_EXT];

_tsplitpath_s(lpDir, lpDrive, 4, NULL, 0, lpFile, _MAX_FNAME, lpExt, _MAX_EXT);

lpDrive[2] = (TCHAR)'\\';
lpDrive[3] = (TCHAR)'\0';

// Watch the directory for file size changes.

dwChangeHandles[0] = FindFirstChangeNotification(
lpDir, // directory to watch
FALSE, // do not watch subtree
FILE_NOTIFY_CHANGE_SIZE); // watch file size changes


// Change notification is set. Now wait on notification handles

while (TRUE)
{ printf("\nWaiting for notification...\n");

dwWaitStatus = WaitForMultipleObjects(1, dwChangeHandles, FALSE, INFINITE);

switch (dwWaitStatus)
{
case WAIT_OBJECT_0:

// A file size changed in the directory.
// do your processing and restart the notification.

_tprintf(TEXT("Directory (%s) changed.\n"), lpDir);

if (FindNextChangeNotification(dwChangeHandles[0]) == FALSE)
{
printf("\n ERROR: FindNextChangeNotification function failed.\n");
ExitProcess(GetLastError());
}
break;

default:
printf("\n ERROR: Unhandled dwWaitStatus.\n");
ExitProcess(GetLastError());
break;
}
}
}