Wait for writes to complete before closing the serial port.

briar-core/src/net/sf/briar/plugins/modem/ModemImpl.java

@@ -33,7 +33,7 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
 	private final Callback callback;
 	private final SerialPort port;
 	private final AtomicBoolean initialised, connected;
-	private final Semaphore offHook;
+	private final Semaphore offHook, writing;
 	private final byte[] line;
 
 	private int lineLen = 0;
@@ -46,6 +46,7 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
 		port = new SerialPort(portName);
 		initialised = new AtomicBoolean(false);
 		offHook = new Semaphore(1);
+		writing = new Semaphore(1);
 		connected = new AtomicBoolean(false);
 		line = new byte[MAX_LINE_LENGTH];
 		reliabilityLayer = new ReliabilityLayer(this);
@@ -151,14 +152,28 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
 	}
 
 	public void handleWrite(byte[] b) throws IOException {
+		try {
+			writing.acquire();
+		} catch(InterruptedException e) {
+			tryToClose(port);
+			Thread.currentThread().interrupt();
+			throw new IOException("Interrupted while waiting to write");
+		}
 		try {
 			port.writeBytes(b);
 		} catch(SerialPortException e) {
 			tryToClose(port);
 			throw new IOException(e.toString());
+		} finally {
+			writing.release();
 		}
 	}
 
+	public void waitForWritesToComplete() throws InterruptedException {
+		writing.acquire();
+		writing.release();
+	}
+
 	public void serialEvent(SerialPortEvent ev) {
 		try {
 			if(ev.isRXCHAR()) {

briar-core/src/net/sf/briar/plugins/modem/ReliabilityLayer.java

@@ -23,6 +23,7 @@ class ReliabilityLayer implements ReadHandler, WriteHandler {
 	private final BlockingQueue<byte[]> writes;
 
 	private volatile boolean valid = true;
+	private volatile Thread writer = null;
 
 	ReliabilityLayer(WriteHandler writeHandler) {
 		this.writeHandler = writeHandler;
@@ -36,7 +37,7 @@ class ReliabilityLayer implements ReadHandler, WriteHandler {
 	}
 
 	void init() {
-		new Thread("ReliabilityLayer") {
+		writer = new Thread("ReliabilityLayer") {
 			@Override
 			public void run() {
 				try {
@@ -58,7 +59,8 @@ class ReliabilityLayer implements ReadHandler, WriteHandler {
 					valid = false;
 				}
 			}
-		}.start();
+		};
+		writer.start();
 	}
 
 	InputStream getInputStream() {
@@ -88,4 +90,9 @@ class ReliabilityLayer implements ReadHandler, WriteHandler {
 		if(LOG.isLoggable(INFO)) LOG.info("Queueing " + b.length + " bytes");
 		if(b.length > 0) writes.add(b);
 	}
+
+	public void waitForWritesToComplete() throws InterruptedException {
+		if(writer != null) writer.join();
+		writeHandler.waitForWritesToComplete();
+	}
 }

briar-core/src/net/sf/briar/plugins/modem/Sender.java

@@ -204,6 +204,10 @@ class Sender {
 		writeHandler.handleWrite(d.getBuffer());
 	}
 
+	void waitForWritesToComplete() throws InterruptedException {
+		writeHandler.waitForWritesToComplete();
+	}
+
 	private static class Outstanding {
 
 		private final Data data;

briar-core/src/net/sf/briar/plugins/modem/SenderOutputStream.java

@@ -23,6 +23,12 @@ class SenderOutputStream extends OutputStream {
 	@Override
 	public void flush() throws IOException {
 		if(offset > Data.HEADER_LENGTH) send(false);
+		try {
+			sender.waitForWritesToComplete();
+		} catch(InterruptedException e) {
+			Thread.currentThread().interrupt();
+			throw new IOException("Interrupted while flushing output stream");
+		}
 	}
 
 	@Override

briar-core/src/net/sf/briar/plugins/modem/SlipEncoder.java

@@ -35,4 +35,8 @@ class SlipEncoder implements WriteHandler {
 		encoded[encodedLength - 1] = END;
 		writeHandler.handleWrite(encoded);
 	}
+
+	public void waitForWritesToComplete() throws InterruptedException {
+		writeHandler.waitForWritesToComplete();
+	}
 }

briar-core/src/net/sf/briar/plugins/modem/WriteHandler.java

@@ -5,4 +5,6 @@ import java.io.IOException;
 interface WriteHandler {
 
 	void handleWrite(byte[] b) throws IOException;
+
+	void waitForWritesToComplete() throws InterruptedException;
 }