    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
    024import org.apache.commons.io.IOUtils;
    025
    026/**
    027 * Data written to this stream is forwarded to a stream that has been associated with this thread.
    028 */
    029public class DemuxInputStream extends InputStream {
    030
    031    private final InheritableThreadLocal<InputStream> inputStreamLocal = new InheritableThreadLocal<>();
    032
    033    /**
    034     * Construct a new instance.
    035     */
    036    public DemuxInputStream() {
    037        // empty
    038    }
    039
    040    /**
    041     * Binds the specified stream to the current thread.
    042     *
    043     * @param input the stream to bind
    044     * @return the InputStream that was previously active
    045     */
    046    public InputStream bindStream(final InputStream input) {
    047        final InputStream oldValue = inputStreamLocal.get();
    048        inputStreamLocal.set(input);
    049        return oldValue;
    050    }
    051
    052    /**
    053     * Closes stream associated with current thread.
    054     *
    055     * @throws IOException if an error occurs
    056     */
    057    @SuppressWarnings("resource") // we actually close the stream here
    058    @Override
    059    public void close() throws IOException {
    060        IOUtils.close(inputStreamLocal.get());
    061    }
    062
    063    /**
    064     * Reads 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() throws IOException {
    071        final InputStream inputStream = inputStreamLocal.get();
    072        if (null != inputStream) {
    073            return inputStream.read();
    074        }
    075        return EOF;
    076    }
    077}