Copyright (c) 2000, 2019 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2019 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.debug.internal.core;


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,
queueing output if the stream is blocked.
The input stream monitor writes to system in via
an output stream.
/**
 * Writes to the input stream of a system process,
 * queueing 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).
/**
	 * The stream which is being written to (connected to system in).
	 */
	private OutputStream fStream;
	
The queue of output.
/**
	 * The queue of output.
	 */
	private Vector<String> fQueue;
	
The thread which writes to the stream.
/**
	 * The thread which writes to the stream.
	 */
	private Thread fThread;
	
A lock for ensuring that writes to the queue are contiguous
/**
	 * A lock for ensuring that writes to the queue are contiguous
	 */
	private Object fLock;

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

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

	
Creates an input stream monitor which writes to system in via the given output stream.
Params:
stream – output stream/**
	 * 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.
Params:
stream – output stream
encoding – stream encoding or null for system default/**
	 * 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<>();
		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.
Params:
text – text to append/**
	 * 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.
/**
	 * Starts a thread which writes the stream.
	 */
	public void startMonitoring() {
		if (fThread == null) {
			fThread = new Thread((Runnable) this::write, DebugCoreMessages.InputStreamMonitor_label);
			fThread.setDaemon(true);
			fThread.start();
		}
	}

	
Close all communications between this
monitor and the underlying stream.
/**
	 * 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.
/**
	 * 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.
/**
	 * Write the text in the queue to the stream.
	 */
	protected void writeNext() {
		while (!fQueue.isEmpty() && !fClosed) {
			String text = 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) {
				// Queue could receive more input between last empty check and
				// lock acquire. See https://bugs.eclipse.org/550834
				if (fQueue.isEmpty()) {
					fLock.wait();
				}
			}
		} catch (InterruptedException e) {
		}
	}

	
Closes the output stream attached to the standard input stream of this
monitor's process.
Throws:
IOException – if an exception occurs closing the input stream/**
	 * 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();
		}

	}
}