fBytesTransferred
fBytesTransferred(0),
fBytesTransferred += size;
off_t BytesTransferred() const { return fBytesTransferred; }
off_t BytesRemaining() const { return fTotalSize - fBytesTransferred; }
off_t fBytesTransferred;
(uint64)fBytesTransferred);
generic_size_t fBytesTransferred;