    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    }