    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     * Binds 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(final InputStream input) {
    040        final InputStream oldValue = inputStreamLocal.get();
    041        inputStreamLocal.set(input);
    042        return oldValue;
    043    }
    044
    045    /**
    046     * Closes stream associated with current thread.
    047     *
    048     * @throws IOException if an error occurs
    049     */
    050    @SuppressWarnings("resource") // we actually close the stream here
    051    @Override
    052    public void close() throws IOException {
    053        IOUtils.close(inputStreamLocal.get());
    054    }
    055
    056    /**
    057     * Reads byte from stream associated with current thread.
    058     *
    059     * @return the byte read from stream
    060     * @throws IOException if an error occurs
    061     */
    062    @SuppressWarnings("resource")
    063    @Override
    064    public int read() throws IOException {
    065        final InputStream inputStream = inputStreamLocal.get();
    066        if (null != inputStream) {
    067            return inputStream.read();
    068        }
    069        return EOF;
    070    }
    071}