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      1 /*
      2  * Licensed to the Apache Software Foundation (ASF) under one or more
      3  * contributor license agreements.  See the NOTICE file distributed with
      4  * this work for additional information regarding copyright ownership.
      5  * The ASF licenses this file to You under the Apache License, Version 2.0
      6  * (the "License"); you may not use this file except in compliance with
      7  * the License.  You may obtain a copy of the License at
      8  *
      9  *      http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  * Unless required by applicable law or agreed to in writing, software
     12  * distributed under the License is distributed on an "AS IS" BASIS,
     13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  * See the License for the specific language governing permissions and
     15  * limitations under the License.
     16  */
     17 package org.apache.commons.io.input;
     18 
     19 import java.io.IOException;
     20 import java.io.InputStream;
     21 
     22 /**
     23  * Data written to this stream is forwarded to a stream that has been associated
     24  * with this thread.
     25  *
     26  * @author <a href="mailto:peter (at) apache.org">Peter Donald</a>
     27  * @version $Revision: 437567 $ $Date: 2006-08-28 07:39:07 +0100 (Mon, 28 Aug 2006) $
     28  */
     29 public class DemuxInputStream
     30     extends InputStream
     31 {
     32     private InheritableThreadLocal m_streams = new InheritableThreadLocal();
     33 
     34     /**
     35      * Bind the specified stream to the current thread.
     36      *
     37      * @param input the stream to bind
     38      * @return the InputStream that was previously active
     39      */
     40     public InputStream bindStream( InputStream input )
     41     {
     42         InputStream oldValue = getStream();
     43         m_streams.set( input );
     44         return oldValue;
     45     }
     46 
     47     /**
     48      * Closes stream associated with current thread.
     49      *
     50      * @throws IOException if an error occurs
     51      */
     52     public void close()
     53         throws IOException
     54     {
     55         InputStream input = getStream();
     56         if( null != input )
     57         {
     58             input.close();
     59         }
     60     }
     61 
     62     /**
     63      * Read byte from stream associated with current thread.
     64      *
     65      * @return the byte read from stream
     66      * @throws IOException if an error occurs
     67      */
     68     public int read()
     69         throws IOException
     70     {
     71         InputStream input = getStream();
     72         if( null != input )
     73         {
     74             return input.read();
     75         }
     76         else
     77         {
     78             return -1;
     79         }
     80     }
     81 
     82     /**
     83      * Utility method to retrieve stream bound to current thread (if any).
     84      *
     85      * @return the input stream
     86      */
     87     private InputStream getStream()
     88     {
     89         return (InputStream)m_streams.get();
     90     }
     91 }
     92