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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.output;
18  
19  import java.io.IOException;
20  import java.io.OutputStream;
21  
22  /**
23   * Forwards data to a stream that has been associated with this thread.
24   *
25   */
26  public class DemuxOutputStream extends OutputStream {
27      private final InheritableThreadLocal<OutputStream> outputStreamThreadLocal = new InheritableThreadLocal<>();
28  
29      /**
30       * Binds the specified stream to the current thread.
31       *
32       * @param output
33       *            the stream to bind
34       * @return the OutputStream that was previously active
35       */
36      public OutputStream bindStream(final OutputStream output) {
37          final OutputStream stream = outputStreamThreadLocal.get();
38          outputStreamThreadLocal.set(output);
39          return stream;
40      }
41  
42      /**
43       * Closes stream associated with current thread.
44       *
45       * @throws IOException
46       *             if an error occurs
47       */
48      @Override
49      public void close() throws IOException {
50          final OutputStream output = outputStreamThreadLocal.get();
51          if (null != output) {
52              output.close();
53          }
54      }
55  
56      /**
57       * Flushes stream associated with current thread.
58       *
59       * @throws IOException
60       *             if an error occurs
61       */
62      @Override
63      public void flush() throws IOException {
64          @SuppressWarnings("resource")
65          final OutputStream output = outputStreamThreadLocal.get();
66          if (null != output) {
67              output.flush();
68          }
69      }
70  
71      /**
72       * Writes byte to stream associated with current thread.
73       *
74       * @param ch
75       *            the byte to write to stream
76       * @throws IOException
77       *             if an error occurs
78       */
79      @Override
80      public void write(final int ch) throws IOException {
81          @SuppressWarnings("resource")
82          final OutputStream output = outputStreamThreadLocal.get();
83          if (null != output) {
84              output.write(ch);
85          }
86      }
87  }