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: 437567 $ $Date: 2006-08-28 07:39:07 +0100 (Mon, 28 Aug 2006) $
028     */
029    public class DemuxInputStream
030        extends InputStream
031    {
032        private InheritableThreadLocal m_streams = new InheritableThreadLocal();
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 = getStream();
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        public void close()
053            throws IOException
054        {
055            InputStream input = getStream();
056            if( null != input )
057            {
058                input.close();
059            }
060        }
061    
062        /**
063         * Read byte from stream associated with current thread.
064         *
065         * @return the byte read from stream
066         * @throws IOException if an error occurs
067         */
068        public int read()
069            throws IOException
070        {
071            InputStream input = getStream();
072            if( null != input )
073            {
074                return input.read();
075            }
076            else
077            {
078                return -1;
079            }
080        }
081    
082        /**
083         * Utility method to retrieve stream bound to current thread (if any).
084         *
085         * @return the input stream
086         */
087        private InputStream getStream()
088        {
089            return (InputStream)m_streams.get();
090        }
091    }