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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 static org.apache.commons.io.IOUtils.EOF;
20  
21  import java.io.IOException;
22  import java.io.InputStream;
23  
24  import org.apache.commons.io.IOUtils;
25  
26  /**
27   * Data written to this stream is forwarded to a stream that has been associated with this thread.
28   */
29  public class DemuxInputStream extends InputStream {
30  
31      private final InheritableThreadLocal<InputStream> inputStreamLocal = new InheritableThreadLocal<>();
32  
33      /**
34       * Binds the specified stream to the current thread.
35       *
36       * @param input the stream to bind
37       * @return the InputStream that was previously active
38       */
39      public InputStream bindStream(final InputStream input) {
40          final InputStream oldValue = inputStreamLocal.get();
41          inputStreamLocal.set(input);
42          return oldValue;
43      }
44  
45      /**
46       * Closes stream associated with current thread.
47       *
48       * @throws IOException if an error occurs
49       */
50      @SuppressWarnings("resource") // we actually close the stream here
51      @Override
52      public void close() throws IOException {
53          IOUtils.close(inputStreamLocal.get());
54      }
55  
56      /**
57       * Reads byte from stream associated with current thread.
58       *
59       * @return the byte read from stream
60       * @throws IOException if an error occurs
61       */
62      @SuppressWarnings("resource")
63      @Override
64      public int read() throws IOException {
65          final InputStream inputStream = inputStreamLocal.get();
66          if (null != inputStream) {
67              return inputStream.read();
68          }
69          return EOF;
70      }
71  }