code: /*
   * 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.commons.io.input;
  
  import java.io.IOException;
  import java.io.InputStream;
  
  /**
   * Data written to this stream is forwarded to a stream that has been associated
   * with this thread.
   *
   * @author <a href="mailto:peter@apache.org">Peter Donald</a>
   * @version $Revision: 736890 $ $Date: 2009-01-23 02:02:22 +0000 (Fri, 23 Jan 2009) $
   */
  public class DemuxInputStream
      extends InputStream
  {
      private final InheritableThreadLocal<InputStream> m_streams = new InheritableThreadLocal<InputStream>();
  
      /**
       * Bind the specified stream to the current thread.
       *
       * @param input the stream to bind
       * @return the InputStream that was previously active
       */
      public InputStream bindStream( InputStream input )
      {
          InputStream oldValue = m_streams.get();
          m_streams.set( input );
          return oldValue;
      }
  
      /**
       * Closes stream associated with current thread.
       *
       * @throws IOException if an error occurs
       */
      @Override
      public void close()
          throws IOException
      {
          InputStream input = m_streams.get();
          if( null != input )
          {
              input.close();
          }
      }
  
      /**
       * Read byte from stream associated with current thread.
       *
       * @return the byte read from stream
       * @throws IOException if an error occurs
       */
      @Override
      public int read()
          throws IOException
      {
          InputStream input = m_streams.get();
          if( null != input )
          {
              return input.read();
          }
          else
          {
              return -1;
          }
      }
  }
  