public void close() throws IOException {
    if (in != null) {
      try {
        in.close();
      } finally {
        in = null;
      }
    }
  }

  /** Closes the current input stream and opens the next one, if any. */
  private void advance() throws IOException {
    close();
    if (it.hasNext()) {
      in = it.next().openStream();
    }
  }

  @Override

 * </pre>
 *
 * </td>
 * <td>
 * Open the Named Pipe foo for reading and writing. The pipe will behave like the <code>CallNamedPipe</code> interface.
 * </td>
 * </tr>
 * <tr>
 * <td >
 *
 * <pre>
 * new SmbNamedPipe("smb://server/IPC$/foo", SmbNamedPipe.PIPE_TYPE_RDWR | SmbNamedPipe.PIPE_TYPE_TRANSACT, context);
 * </pre>
 *
 * </td>
 * <td>

 *         SmbNamedPipe.PIPE_TYPE_CALL );
 * </pre></td><td>
 * Open the Named Pipe foo for reading and writing. The pipe will behave like the <code>CallNamedPipe</code> interface.
 * </td></tr>
 * <tr><td ><pre>
 * new SmbNamedPipe( "smb1://server/IPC$/foo",
 *         SmbNamedPipe.PIPE_TYPE_RDWR |
 *         SmbNamedPipe.PIPE_TYPE_TRANSACT );
 * </pre></td><td>

 *
 * @since 14.0
 * @author Colin Decker
 */
@J2ktIncompatible
@GwtIncompatible
public abstract class CharSink {

  /** Constructor for use by subclasses. */
  protected CharSink() {}

  /**
   * Opens a new {@link Writer} for writing to this sink. This method returns a new, independent
   * writer each time it is called.
   *
   * <p>The caller is responsible for ensuring that the returned writer is closed.
   *

   * the source will contain the concatenated data from the streams of the underlying sources.
   *
   * <p>Only one underlying stream will be open at a time. Closing the concatenated stream will
   * close the open underlying stream.
   *
   * @param sources the sources to concatenate
   * @return a {@code ByteSource} containing the concatenated data
   * @since 15.0
   */

        }
        return results;
    }

    /**
     * Opens a directory for enumeration
     *
     * @return the opened directory file entry
     * @throws CIFSException if an error occurs opening the directory
     */
    @SuppressWarnings("resource")
    @Override
    protected FileEntry open() throws CIFSException {
        final SmbTreeHandleImpl th = getTreeHandle();

            return advance(true);
        }
        return null;
    }

    /**
     * Opens the enumeration and returns the first entry.
     *
     * @return the first file entry, or null if empty
     * @throws CIFSException if an error occurs during opening
     */
    protected abstract FileEntry open() throws CIFSException;

    /**
     * Checks if the enumeration is complete.
     *

        // Act + Assert (no exception expected)
        assertDoesNotThrow(() -> SmbCopyUtil.copyFile(src, dest, buffers, 1, new WriterThread(), sh, dh));

        // Verify that server-side path engaged at least the initial opens
        verify(src, times(1)).openUnshared(anyInt(), anyInt(), anyInt(), anyInt(), anyInt());
        verify(dest, times(1)).openUnshared(anyInt(), anyInt(), anyInt(), anyInt(), anyInt());
    }

        assertTrue(ex2.getMessage().contains("Already closed"));
    }

    @Test
    @DisplayName("ensureOpen opens SMB2 via UNC path and marks open")
    void ensureOpen_smb2_opens() throws Exception {
        // Arrange
        SmbPipeHandleImpl handle = newHandleWithBasicStubs(0, "\\\\pipe\\\\foo");

            this.maxSpan = options.maxSpan;

        if (typeof options.dateLimit === 'object') //backwards compat
            this.maxSpan = options.dateLimit;

        if (typeof options.opens === 'string')
            this.opens = options.opens;

        if (typeof options.drops === 'string')
            this.drops = options.drops;

        if (typeof options.showWeekNumbers === 'boolean')