content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  package org.apache.guacamole.net;
  
  
  import java.util.UUID;
  import org.apache.guacamole.GuacamoleException;
  import org.apache.guacamole.io.GuacamoleReader;
  import org.apache.guacamole.io.GuacamoleWriter;
  
  /**
   * Provides a unique identifier and synchronized access to the GuacamoleReader
   * and GuacamoleWriter associated with a GuacamoleSocket.
   *
   * @author Michael Jumper
   */
  public interface GuacamoleTunnel {
  
      /**
       * The Guacamole protocol instruction opcode reserved for arbitrary
       * internal use by tunnel implementations. The value of this opcode is
       * guaranteed to be the empty string (""). Tunnel implementations may use
       * this opcode for any purpose. It is currently used by the HTTP tunnel to
       * mark the end of the HTTP response, and by the WebSocket tunnel to
       * transmit the tunnel UUID.
       */
      static final String INTERNAL_DATA_OPCODE = "";
  
      /**
       * Acquires exclusive read access to the Guacamole instruction stream
       * and returns a GuacamoleReader for reading from that stream.
       *
       * @return A GuacamoleReader for reading from the Guacamole instruction
       *         stream.
       */
      GuacamoleReader acquireReader();
  
      /**
       * Relinquishes exclusive read access to the Guacamole instruction
       * stream. This function should be called whenever a thread finishes using
       * a GuacamoleTunnel's GuacamoleReader.
       */
      void releaseReader();
  
      /**
       * Returns whether there are threads waiting for read access to the
       * Guacamole instruction stream.
       *
       * @return true if threads are waiting for read access the Guacamole
       *         instruction stream, false otherwise.
       */
      boolean hasQueuedReaderThreads();
  
      /**
       * Acquires exclusive write access to the Guacamole instruction stream
       * and returns a GuacamoleWriter for writing to that stream.
       *
       * @return A GuacamoleWriter for writing to the Guacamole instruction
       *         stream.
       */
      GuacamoleWriter acquireWriter();
  
      /**
       * Relinquishes exclusive write access to the Guacamole instruction
       * stream. This function should be called whenever a thread finishes using
       * a GuacamoleTunnel's GuacamoleWriter.
       */
      void releaseWriter();
  
      /**
       * Returns whether there are threads waiting for write access to the
       * Guacamole instruction stream.
       *
       * @return true if threads are waiting for write access the Guacamole
       *         instruction stream, false otherwise.
       */
      boolean hasQueuedWriterThreads();
  
      /**
       * Returns the unique identifier associated with this GuacamoleTunnel.
       *
       * @return The unique identifier associated with this GuacamoleTunnel.
       */
      UUID getUUID();
  
      /**
       * Returns the GuacamoleSocket used by this GuacamoleTunnel for reading
       * and writing.
       *
       * @return The GuacamoleSocket used by this GuacamoleTunnel.
       */
      GuacamoleSocket getSocket();
  
      /**
       * Release all resources allocated to this GuacamoleTunnel.
       *
       * @throws GuacamoleException if an error occurs while releasing
       *                            resources.
       */
      void close() throws GuacamoleException;
  
      /**
       * Returns whether this GuacamoleTunnel is open, or has been closed.
       *
       * @return true if this GuacamoleTunnel is open, false if it is closed.
       */
      boolean isOpen();
  
  }
  