InputStreamMonitor.java

/*******************************************************************************
 * Copyright (c) 2012 Sierra Wireless and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Sierra Wireless - initial API and implementation
 *******************************************************************************/
//FIXME This class is a copy from eclipse.debug.core plugin
package org.eclipse.koneki.ldt.remote.debug.core.internal.sshprocess;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Vector;

import org.eclipse.debug.core.DebugPlugin;

/**
 * Writes to the input stream of a system process, queuing output if the stream is blocked.
 * 
 * The input stream monitor writes to system in via an output stream.
 */
public class InputStreamMonitor {

	/**
	 * The stream which is being written to (connected to system in).
	 */
	private OutputStream fStream;
	/**
	 * The queue of output.
	 */
	private Vector<String> fQueue;

	/**
	 * The thread which writes to the stream.
	 */
	private Thread fThread;
	/**
	 * A lock for ensuring that writes to the queue are contiguous
	 */
	private Object fLock;

	/**
	 * Whether the underlying output stream has been closed
	 */
	private boolean fClosed = false;

	/**
	 * The encoding of the input stream.
	 */
	private String fEncoding;

	/**
	 * Creates an input stream monitor which writes to system in via the given output stream.
	 * 
	 * @param stream
	 *            output stream
	 */
	public InputStreamMonitor(OutputStream stream) {
		this(stream, null);
	}

	/**
	 * Creates an input stream monitor which writes to system in via the given output stream.
	 * 
	 * @param stream
	 *            output stream
	 * @param encoding
	 *            stream encoding or <code>null</code> for system default
	 */
	public InputStreamMonitor(OutputStream stream, String encoding) {
		fStream = stream;
		fQueue = new Vector<String>();
		fLock = new Object();
		fEncoding = encoding;
	}

	/**
	 * Appends the given text to the stream, or queues the text to be written at a later time if the stream is blocked.
	 * 
	 * @param text
	 *            text to append
	 */
	public void write(String text) {
		synchronized (fLock) {
			fQueue.add(text);
			fLock.notifyAll();
		}
	}

	/**
	 * Starts a thread which writes the stream.
	 */
	public void startMonitoring() {
		if (fThread == null) {
			fThread = new Thread(new Runnable() {
				public void run() {
					write();
				}
			}, "Input Stream Monitor"); //$NON-NLS-1$
			fThread.setDaemon(true);
			fThread.start();
		}
	}

	/**
	 * Close all communications between this monitor and the underlying stream.
	 */
	public void close() {
		if (fThread != null) {
			Thread thread = fThread;
			fThread = null;
			thread.interrupt();
		}
	}

	/**
	 * Continuously writes to the stream.
	 */
	protected void write() {
		while (fThread != null) {
			writeNext();
		}
		if (!fClosed) {
			try {
				fStream.close();
			} catch (IOException e) {
				DebugPlugin.log(e);
			}
		}
	}

	/**
	 * Write the text in the queue to the stream.
	 */
	protected void writeNext() {
		while (!fQueue.isEmpty() && !fClosed) {
			String text = (String) fQueue.firstElement();
			fQueue.removeElementAt(0);
			try {
				if (fEncoding != null)
					fStream.write(text.getBytes(fEncoding));
				else
					fStream.write(text.getBytes());
				fStream.flush();
			} catch (IOException e) {
				DebugPlugin.log(e);
			}
		}
		try {
			synchronized (fLock) {
				fLock.wait();
			}
			// CHECKSTYLE:OFF
		} catch (InterruptedException e) {
			// CHECKSTYLE:ON
		}

	}

	/**
	 * Closes the output stream attached to the standard input stream of this monitor's process.
	 * 
	 * @exception IOException
	 *                if an exception occurs closing the input stream
	 */
	public void closeInputStream() throws IOException {
		if (!fClosed) {
			fClosed = true;
			fStream.close();
		} else {
			throw new IOException();
		}

	}
}