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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@apache.org">Peter Donald</a>
27   * @version $Revision: 437567 $ $Date: 2006-08-28 08:39:07 +0200 (Mo, 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  }