sr.sp = sr.sp[1:] // Ensure last fragment always remains
		}
	}

	// If the last fragment is a hole, then seek to 1-byte before EOF, and
	// write a single byte to ensure the file is the right size.
	if writeLastByte && err == nil {
		_, err = ws.Write([]byte{0})
		sr.pos++
	}

	n = sr.pos - pos0
	switch {
	case err == io.EOF:
		return n, errMissData // Less data in dense file than sparse file