StreamPumper.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.commons.exec;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.commons.exec.util.DebugUtils;

/**
 * Copies all data from an input stream to an output stream.
 */
public class StreamPumper implements Runnable {

    /** The default size of the internal buffer for copying the streams. */
    private static final int DEFAULT_SIZE = 1024;

    /** The input stream to pump from. */
    private final InputStream is;

    /** The output stream to pmp into. */
    private final OutputStream os;

    /** The size of the internal buffer for copying the streams. */
    private final int size;

    /** Was the end of the stream reached. */
    private boolean finished;

    /** Close the output stream when exhausted. */
    private final boolean closeWhenExhausted;

    /**
     * Constructs a new stream pumper.
     *
     * @param is input stream to read data from.
     * @param os output stream to write data to.
     */
    public StreamPumper(final InputStream is, final OutputStream os) {
        this(is, os, false);
    }

    /**
     * Constructs a new stream pumper.
     *
     * @param is                 input stream to read data from.
     * @param os                 output stream to write data to.
     * @param closeWhenExhausted if true, the output stream will be closed when the input is exhausted.
     */
    public StreamPumper(final InputStream is, final OutputStream os, final boolean closeWhenExhausted) {
        this.is = is;
        this.os = os;
        this.size = DEFAULT_SIZE;
        this.closeWhenExhausted = closeWhenExhausted;
    }

    /**
     * Constructs a new stream pumper.
     *
     * @param is                 input stream to read data from.
     * @param os                 output stream to write data to.
     * @param closeWhenExhausted if true, the output stream will be closed when the input is exhausted.
     * @param size               the size of the internal buffer for copying the streams.
     */
    public StreamPumper(final InputStream is, final OutputStream os, final boolean closeWhenExhausted, final int size) {
        this.is = is;
        this.os = os;
        this.size = size > 0 ? size : DEFAULT_SIZE;
        this.closeWhenExhausted = closeWhenExhausted;
    }

    /**
     * Tests whether the end of the stream has been reached.
     *
     * @return true is the stream has been exhausted.
     */
    public synchronized boolean isFinished() {
        return finished;
    }

    /**
     * Copies data from the input stream to the output stream. Terminates as soon as the input stream is closed or an error occurs.
     */
    @Override
    public void run() {
        synchronized (this) {
            // Just in case this object is reused in the future
            finished = false;
        }

        final byte[] buf = new byte[this.size];

        int length;
        try {
            while ((length = is.read(buf)) > 0) {
                os.write(buf, 0, length);
            }
        } catch (final Exception ignored) {
            // nothing to do - happens quite often with watchdog
        } finally {
            if (closeWhenExhausted) {
                try {
                    os.close();
                } catch (final IOException e) {
                    final String msg = "Got exception while closing exhausted output stream";
                    DebugUtils.handleException(msg, e);
                }
            }
            synchronized (this) {
                finished = true;
                notifyAll();
            }
        }
    }

    /**
     * This method blocks until the stream pumper finishes.
     *
     * @throws InterruptedException if any thread interrupted the current thread before or while the current thread was waiting for a notification.
     * @see #isFinished()
     */
    public synchronized void waitFor() throws InterruptedException {
        while (!isFinished()) {
            wait();
        }
    }
}