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 */
017package org.apache.commons.io.input;
018
019import static org.apache.commons.io.IOUtils.EOF;
020
021import java.io.IOException;
022import java.io.InputStream;
023
024/**
025 * Data written to this stream is forwarded to a stream that has been associated
026 * with this thread.
027 *
028 */
029public class DemuxInputStream
030    extends InputStream
031{
032    private final InheritableThreadLocal<InputStream> 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( final InputStream input )
041    {
042        final 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        final 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        final InputStream input = m_streams.get();
074        if( null != input )
075        {
076            return input.read();
077        }
078        else
079        {
080            return EOF;
081        }
082    }
083}