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.

And what exactly did you expect 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 - for example zero is a perfectly valid "size" for a directory in one way to view it - 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.

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Mats

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?

Quote:

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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

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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...

Quote:

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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.

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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.

Quote:

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FindFirst / FindNext is the way to do it.

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

If by the size of directory, you mean the size of the files IN the directory, the no, GetFileSize will not return that. It _MAY_ give you the size of the actual content in the directory, but as it turns out, it doesn't - it returns zero - which is a valid return value (e.g. it's the number of bytes of data that you can read out of the directory - it may return other values if you have ACL attributes or other "extra metadata" that is sort of part of the user-data belonging to a directory), but not particularly meaningful if you want to know the size of the files in the directory.

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Mats

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.

Two side notes:

1) GetFileSize() doesn't return 0 on error.
2) The GetFileSize() MSDN page mentions no less than three times that you shouldn't use it. You should use GetFileSizeEx() instead, which doesn't have a braindead interface.

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

Code:

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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;
}

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The only problem with the FindNextFile/FindFirstFile is that they won't return directories if you use any other pattern than *.*. Keep that in mind. Otherwise it seems correct.