Calculate NTFS and FAT file sytem size in Windows

Does anybody know how to calculate the amount of space occupied by the file system alone?

I am trying to calculate how much space files and directories occupy in a disk without iterating thru the entire disk.

this is a sample i开发者_如何学运维n C++:

ULARGE_INTEGER freeBytesAvailable, totalNumberOfBytes, totalNumberOfFreeBytes;
GetDiskFreeSpaceEx(NULL, &freeBytesAvailable, &totalNumberOfBytes, &totalNumberOfFreeBytes);
mCurrentProgress = 0;
mTotalProgress = totalNumberOfBytes.QuadPart - totalNumberOfFreeBytes.QuadPart;

But the problem is that I need to exclude the size of the file system but I have no idea if it is possible or if there is an API to get this info.

Doesn't make sense. On NTFS, small files are stored in the directory. I mean literally, they're inlined. The same sector that holds the filename also holds the file contents. Therefore, you can't count that sector as either "used for files" or "used for file system overhead".