return nil, 0, 0, err
		}
		var decSize int64
		decSize, err = oi.DecryptedSize()
		if err != nil {
			return nil, 0, 0, err
		}
		var decRangeLength int64
		decRangeLength, err = rs.GetLength(decSize)
		if err != nil {
			return nil, 0, 0, err
		}

		// We define a closure that performs decryption given
		// a reader that returns the desired range of