Thread: GetFileSize() and directories

Hi,

I'm trying to get the size of a directory and I came up with two ways...
1. I used FindFirstFile() and FindNextFile() and searched the directory tree for files, adding the size of each file and finally getting the directory size.
2. I opened the directory with CreateFile() using the FILE_FLAG_BACKUP_SEMANTICS flag and then called GetFileSize() with the handle returned from CreateFile(). Even though MSDN says that one can pass such handles to GetFileSize(), the function keeps returning 0 and GetLastError() returns 0 indicating no error has occurred.

I can't really understand why GetFileSize() returns 0 instead of the actual directory size, so if anyone has some answers or any other methods of getting the size of a directory that would be great.

Thanks.

FindFirst / FindNext is the way to do it.

gg

I expected to get back the correct directory size, what else could I have expected to get back?

just because you can pass in a handle to a function and not receive an error doesn't mean that the function will necessarily do what you expect it to do

Well, right, not what I expect it to do but what it's supposed to do...
So if GetFileSize() is supposed to retrieve the size of a directory, why would it return 0 bytes (that is, an incorrect size) and pretend not to fail? Maybe it's not supposed to return directory sizes after all...

there is no other information in a directory than a list of files, and you don't "read" directories that way, and I expect that even BackupRead on a directory will return zero bytes read.

I am aware of that, as I said, at first I successfully used the FindFirstFile() and FindNextFile() APIs to compute the size, but then I don't see why Windows would let you use GetFileSize() on directory handles (opened using CreateFile() and FILE_FLAG_BACKUP_SEMANTICS) knowing that it doesn't do anything.

FindFirst / FindNext is the way to do it.

That's how it worked for me but I thought there are other methods too...

This is also logical as far as file systems go - FAT/NTFS in particular do not store the size of a folder anywhere, so to call GetFileSize on one, assuming it wasn't handled by a special case (which it is, hence not a failure), would have Windows take one look at the file system and come back with "Nope, I can't see a size value there".

It doesn't fail because of those situations where you're iterating the sizes of everything within a folder, which may include other folders. A badly-caught failure will mess up the running total you have. Otherwise you'll have the correct size of the files.

Thanks for the answers guys and here's how I implemented my GetDirectorySize() function...

Code:

BOOL MyGetFileSize (const TCHAR * szPath, ULONGLONG * ptrSize)
{
	LARGE_INTEGER size;
	HANDLE hFile;
	
	hFile = CreateFile (szPath, 0, FILE_SHARE_READ, 0, OPEN_EXISTING, 0, 0);
	
	if (hFile != INVALID_HANDLE_VALUE) {
		if (GetFileSizeEx (hFile, &size)) {
			*ptrSize = size.QuadPart;
			CloseHandle (hFile);
			return TRUE;
		} else {
			CloseHandle (hFile);
			return FALSE;
		}
	}
	
	return FALSE;
}

// GetDirectorySize(), stores the directory size (in bytes) in 'ptrSize' and returns TRUE to indicate no error occurred 
// or FALSE to indicate that something went wrong and the size might not be accurate
// WARNING: You need to append a '\' to the directory name before calling the function
BOOL GetDirectorySize (const TCHAR * szPath, ULONGLONG * ptrSize)
{
	WIN32_FIND_DATA find;
	BOOL returnCode = TRUE;
	HANDLE hFind;
	TCHAR * szFullPath = (TCHAR *) malloc ((MAX_PATH + 1)* sizeof (TCHAR));

	// WARNING: You need to append a '\' to the directory name before calling the function
	wsprintf (szFullPath, TEXT("%s*"), szPath);
	hFind = FindFirstFile (szFullPath, &find);
	
	if (hFind == INVALID_HANDLE_VALUE) {
		return FALSE;
	}
	
	// Are we dealing with a directory
	if (find.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
	{
		if (lstrcmp (find.cFileName, TEXT(".")) && lstrcmp (find.cFileName, TEXT("..")))
		{
			size_t pos = lstrlen (find.cFileName) - 1;
			if (find.cFileName[pos] != '\\') {
				find.cFileName[pos+1] = '\\';
				find.cFileName[pos+2] = 0;
			}
			
			wsprintf (szFullPath, TEXT("%s%s"), szPath, find.cFileName);
			returnCode &= GetDirectorySize (szFullPath, ptrSize);
		}
	}
	else // ... or are we dealing with a file
	{
		ULONGLONG fileSize = 0;
		wsprintf (szFullPath, TEXT("%s%s"), szPath, find.cFileName);

		if (MyGetFileSize (szFullPath, &fileSize))
			*ptrSize = (*ptrSize) + fileSize;
		else
			returnCode = FALSE;
	}

	while (FindNextFile (hFind, &find))
	{
		// Are we dealing with a directory
		if (find.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
		{
			if (lstrcmp (find.cFileName, TEXT(".")) && lstrcmp (find.cFileName, TEXT("..")))
			{
				size_t pos = lstrlen (find.cFileName) - 1;
				if (find.cFileName[pos] != L'\\') {
					find.cFileName[pos+1] = L'\\';
					find.cFileName[pos+2] = 0;
				}
			
				wsprintf (szFullPath, TEXT("%s%s"), szPath, find.cFileName);
				returnCode &= GetDirectorySize (szFullPath, ptrSize);
			}
		} 
		else // ... or are we dealing with a file
		{
			ULONGLONG fileSize = 0;
			wsprintf (szFullPath, TEXT("%s%s"), szPath, find.cFileName);
			if (MyGetFileSize (szFullPath, &fileSize))
				*ptrSize = (*ptrSize) + fileSize;
			else
				returnCode = FALSE;
		}
	}

	if (GetLastError() != ERROR_NO_MORE_FILES)
		returnCode = FALSE;


	FindClose (hFind);
	free (szFullPath);
	return returnCode;
}