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 07:39:07 +0100 (Mon, 28 Aug 2006) $
28  */
29 public class DemuxInputStream
30     extends InputStream
31 {
32     private InheritableThreadLocal<InputStream> m_streams = new InheritableThreadLocal<InputStream>();
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      */
bindStream( InputStream input )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     @Override
close()53     public void close()
54         throws IOException
55     {
56         InputStream input = getStream();
57         if( null != input )
58         {
59             input.close();
60         }
61     }
62 
63     /**
64      * Read byte from stream associated with current thread.
65      *
66      * @return the byte read from stream
67      * @throws IOException if an error occurs
68      */
69     @Override
read()70     public int read()
71         throws IOException
72     {
73         InputStream input = getStream();
74         if( null != input )
75         {
76             return input.read();
77         }
78         else
79         {
80             return -1;
81         }
82     }
83 
84     /**
85      * Utility method to retrieve stream bound to current thread (if any).
86      *
87      * @return the input stream
88      */
getStream()89     private InputStream getStream()
90     {
91         return m_streams.get();
92     }
93 }
94