001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     * 
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     * 
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.io.input;
018    
019    import java.io.IOException;
020    import java.io.InputStream;
021    
022    /**
023     * Data written to this stream is forwarded to a stream that has been associated
024     * with this thread.
025     *
026     * @author <a href="mailto:peter@apache.org">Peter Donald</a>
027     * @version $Revision: 736890 $ $Date: 2009-01-23 02:02:22 +0000 (Fri, 23 Jan 2009) $
028     */
029    public class DemuxInputStream
030        extends InputStream
031    {
032        private final InheritableThreadLocal<InputStream> m_streams = new InheritableThreadLocal<InputStream>();
033    
034        /**
035         * Bind the specified stream to the current thread.
036         *
037         * @param input the stream to bind
038         * @return the InputStream that was previously active
039         */
040        public InputStream bindStream( InputStream input )
041        {
042            InputStream oldValue = m_streams.get();
043            m_streams.set( input );
044            return oldValue;
045        }
046    
047        /**
048         * Closes stream associated with current thread.
049         *
050         * @throws IOException if an error occurs
051         */
052        @Override
053        public void close()
054            throws IOException
055        {
056            InputStream input = m_streams.get();
057            if( null != input )
058            {
059                input.close();
060            }
061        }
062    
063        /**
064         * Read byte from stream associated with current thread.
065         *
066         * @return the byte read from stream
067         * @throws IOException if an error occurs
068         */
069        @Override
070        public int read()
071            throws IOException
072        {
073            InputStream input = m_streams.get();
074            if( null != input )
075            {
076                return input.read();
077            }
078            else
079            {
080                return -1;
081            }
082        }
083    }