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     * @version $Id: DemuxInputStream.java 1302056 2012-03-18 03:03:38Z ggregory $
027     */
028    public class DemuxInputStream
029        extends InputStream
030    {
031        private final InheritableThreadLocal<InputStream> m_streams = new InheritableThreadLocal<InputStream>();
032    
033        /**
034         * Bind the specified stream to the current thread.
035         *
036         * @param input the stream to bind
037         * @return the InputStream that was previously active
038         */
039        public InputStream bindStream( InputStream input )
040        {
041            InputStream oldValue = m_streams.get();
042            m_streams.set( input );
043            return oldValue;
044        }
045    
046        /**
047         * Closes stream associated with current thread.
048         *
049         * @throws IOException if an error occurs
050         */
051        @Override
052        public void close()
053            throws IOException
054        {
055            InputStream input = m_streams.get();
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        @Override
069        public int read()
070            throws IOException
071        {
072            InputStream input = m_streams.get();
073            if( null != input )
074            {
075                return input.read();
076            }
077            else
078            {
079                return -1;
080            }
081        }
082    }