StreamCopyThread.java

/*
 * Copyright (C) 2009-2010, Google Inc. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.util.io;

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

/**
 * Thread to copy from an input stream to an output stream.
 */
public class StreamCopyThread extends Thread {
    private static final int BUFFER_SIZE = 1024;

    private final InputStream src;

    private final OutputStream dst;

    private volatile boolean done;

    /** Lock held by flush to avoid interrupting a write. */
    private final Object writeLock;

    /**
     * Create a thread to copy data from an input stream to an output stream.
     *
     * @param i
     *            stream to copy from. The thread terminates when this stream
     *            reaches EOF. The thread closes this stream before it exits.
     * @param o
     *            stream to copy into. The destination stream is automatically
     *            closed when the thread terminates.
     */
    public StreamCopyThread(InputStream i, OutputStream o) {
        setName(Thread.currentThread().getName() + "-StreamCopy"); //$NON-NLS-1$
        src = i;
        dst = o;
        writeLock = new Object();
    }

    /**
     * Request that the thread terminate, and wait for it.
     * <p>
     * This method signals to the copy thread that it should stop as soon as
     * there is no more IO occurring.
     *
     * @throws java.lang.InterruptedException
     *             the calling thread was interrupted.
     */
    public void halt() throws InterruptedException {
        for (;;) {
            join(250 /* milliseconds */);
            if (isAlive()) {
                done = true;
                interrupt();
            } else
                break;
        }
    }

    /** {@inheritDoc} */
    @Override
    public void run() {
        try {
            final byte[] buf = new byte[BUFFER_SIZE];
            boolean readInterrupted = false;
            for (;;) {
                try {
                    if (readInterrupted) {
                        synchronized (writeLock) {
                            boolean interruptedAgain = Thread.interrupted();
                            dst.flush();
                            if (interruptedAgain) {
                                interrupt();
                            }
                        }
                        readInterrupted = false;
                    }

                    if (done)
                        break;

                    final int n;
                    try {
                        n = src.read(buf);
                    } catch (InterruptedIOException wakey) {
                        readInterrupted = true;
                        continue;
                    }
                    if (n < 0)
                        break;

                    synchronized (writeLock) {
                        boolean writeInterrupted = Thread.interrupted();
                        dst.write(buf, 0, n);
                        if (writeInterrupted) {
                            interrupt();
                        }
                    }
                } catch (IOException e) {
                    break;
                }
            }
        } finally {
            try {
                src.close();
            } catch (IOException e) {
                // Ignore IO errors on close
            }
            try {
                dst.close();
            } catch (IOException e) {
                // Ignore IO errors on close
            }
        }
    }
}