func (bs *ByteStream) ReadAt(b []byte, off int64) (n int, err error) {
	if len(b) == 0 {
		return 0, nil
	}
	n, err = bs.r.ReadAt(b, off)
	bs.pos += n
	return
}
// ReadAt len(b) bytes from the underlying stream at a given offset.
ReadAt len(b) bytes from the underlying stream at a given offset.
// ReadAt len ( b ) bytes from the underlying stream at a given offset .
func (bs *ByteStream) ReadAt(b []byte, off int64) (n int, err error) {
	if len(b) == 0 {
		return 0, nil
	}
	n, err = bs.r.ReadAt(b, off)
	bs.pos += n
	return
}
func ( bs * ByteStream ) ReadAt ( b [ ] byte , off int64 ) ( n int , err error ) { if len ( b ) == 0 { return 0 , nil } n , err = bs . r . ReadAt ( b , off ) bs . pos += n return }
ReadAt len(b) bytes from the underlying stream at a given offset.
ReadAt len ( b ) bytes from the underlying stream at a given offset .