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+/*******************************************************************************
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+ * Copyright (c) 2014 Sebastian Stenzel
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+ * This file is licensed under the terms of the MIT license.
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+ * See the LICENSE.txt file for more info.
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+ *
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+ * Contributors:
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+ * Sebastian Stenzel - initial API and implementation
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+ ******************************************************************************/
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+package org.cryptomator.ui.util;
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+
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+import java.io.Closeable;
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+import java.io.IOException;
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+import java.net.InetAddress;
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+import java.net.InetSocketAddress;
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+import java.nio.ByteBuffer;
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+import java.nio.channels.ClosedChannelException;
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+import java.nio.channels.ClosedSelectorException;
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+import java.nio.channels.ReadableByteChannel;
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+import java.nio.channels.SelectableChannel;
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+import java.nio.channels.SelectionKey;
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+import java.nio.channels.Selector;
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+import java.nio.channels.ServerSocketChannel;
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+import java.nio.channels.SocketChannel;
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+import java.nio.channels.WritableByteChannel;
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+import java.util.HashSet;
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+import java.util.Objects;
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+import java.util.Optional;
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+import java.util.Set;
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+import java.util.concurrent.ExecutorService;
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+import java.util.prefs.Preferences;
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+
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+import org.apache.commons.io.IOUtils;
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+import org.cryptomator.ui.Main;
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+import org.cryptomator.ui.util.ListenerRegistry.ListenerRegistration;
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+import org.slf4j.Logger;
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+import org.slf4j.LoggerFactory;
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+
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+/**
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+ * Classes and methods to manage running this application in a mode, which only
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+ * shows one instance.
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+ *
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+ * @author Tillmann Gaida
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+ */
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+public class SingleInstanceManager {
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+ private static final Logger LOG = LoggerFactory.getLogger(SingleInstanceManager.class);
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+
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+ /**
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+ * Connection to a running instance
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+ */
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+ public static class RemoteInstance implements Closeable {
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+ final SocketChannel channel;
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+
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+ RemoteInstance(SocketChannel channel) {
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+ super();
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+ this.channel = channel;
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+ }
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+
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+ /**
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+ * Sends a message to the running instance.
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+ *
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+ * @param string
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+ * May not be longer than 2^16 - 1 bytes.
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+ * @param timeout
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+ * timeout in milliseconds. this should be larger than the
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+ * precision of {@link System#currentTimeMillis()}.
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+ * @return true if the message was sent within the given timeout.
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+ * @throws IOException
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+ */
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+ public boolean sendMessage(String string, long timeout) throws IOException {
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+ Objects.requireNonNull(string);
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+ byte[] message = string.getBytes();
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+ if (message.length >= 256 * 256) {
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+ throw new IOException("Message too long.");
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+ }
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+
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+ ByteBuffer buf = ByteBuffer.allocate(message.length + 2);
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+ buf.put((byte) (message.length / 256));
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+ buf.put((byte) (message.length % 256));
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+ buf.put(message);
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+
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+ buf.flip();
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+ TimeoutTask.attempt(t -> {
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+ if (channel.write(buf) < 0) {
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+ return true;
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+ }
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+ return !buf.hasRemaining();
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+ }, timeout, 10);
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+ return !buf.hasRemaining();
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+ }
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+
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+ @Override
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+ public void close() throws IOException {
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+ channel.close();
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+ }
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+
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+ public int getRemotePort() throws IOException {
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+ return ((InetSocketAddress) channel.getRemoteAddress()).getPort();
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+ }
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+ }
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+
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+ public static interface MessageListener {
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+ void handleMessage(String message);
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+ }
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+
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+ /**
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+ * Represents a socket making this the main instance of the application.
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+ */
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+ public static class LocalInstance implements Closeable {
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+ private class ChannelState {
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+ ByteBuffer write = ByteBuffer.wrap(applicationKey.getBytes());
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+ ByteBuffer readLength = ByteBuffer.allocate(2);
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+ ByteBuffer readMessage = null;
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+ }
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+
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+ final ListenerRegistry<MessageListener, String> registry = new ListenerRegistry<>(MessageListener::handleMessage);
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+ final String applicationKey;
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+ final ServerSocketChannel channel;
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+ final Selector selector;
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+ int port = 0;
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+
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+ public LocalInstance(String applicationKey, ServerSocketChannel channel, Selector selector) {
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+ Objects.requireNonNull(applicationKey);
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+ this.applicationKey = applicationKey;
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+ this.channel = channel;
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+ this.selector = selector;
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+ }
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+
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+ /**
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+ * Register a listener for
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+ *
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+ * @param listener
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+ * @return
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+ */
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+ public ListenerRegistration registerListener(MessageListener listener) {
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+ Objects.requireNonNull(listener);
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+ return registry.registerListener(listener);
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+ }
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+
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+ void handleSelection(SelectionKey key) throws IOException {
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+ if (key.isAcceptable()) {
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+ final SocketChannel accepted = channel.accept();
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+ if (accepted != null) {
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+ LOG.info("accepted incoming connection");
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+ accepted.configureBlocking(false);
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+ accepted.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
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+ }
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+ }
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+
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+ if (key.attachment() == null) {
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+ key.attach(new ChannelState());
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+ }
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+
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+ ChannelState state = (ChannelState) key.attachment();
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+
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+ if (key.isWritable() && state.write != null) {
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+ ((WritableByteChannel) key.channel()).write(state.write);
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+ if (!state.write.hasRemaining()) {
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+ state.write = null;
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+ }
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+ LOG.debug("wrote welcome. switching to read only.");
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+ key.interestOps(SelectionKey.OP_READ);
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+ }
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+
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+ if (key.isReadable()) {
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+ ByteBuffer buffer = state.readLength != null ? state.readLength : state.readMessage;
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+
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+ if (((ReadableByteChannel) key.channel()).read(buffer) < 0) {
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+ key.cancel();
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+ }
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+
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+ if (!buffer.hasRemaining()) {
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+ buffer.flip();
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+ if (state.readLength != null) {
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+ int length = (buffer.get() + 256) % 256;
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+ length = length * 256 + ((buffer.get() + 256) % 256);
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+
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+ state.readLength = null;
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+ state.readMessage = ByteBuffer.allocate(length);
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+ } else {
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+ byte[] bytes = new byte[buffer.limit()];
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+ buffer.get(bytes);
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+
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+ state.readMessage = null;
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+ state.readLength = ByteBuffer.allocate(2);
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+
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+ registry.broadcast(new String(bytes, "UTF-8"));
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+ }
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+ }
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+ }
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+ }
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+
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+ public void close() {
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+ IOUtils.closeQuietly(selector);
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+ IOUtils.closeQuietly(channel);
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+ if (getSavedPort(applicationKey).orElse(-1).equals(port)) {
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+ Preferences.userNodeForPackage(Main.class).remove(applicationKey);
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+ }
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+ }
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+
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+ void selectionLoop() {
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+ try {
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+ final Set<SelectionKey> keysToRemove = new HashSet<>();
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+ while (selector.select() > 0) {
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+ final Set<SelectionKey> keys = selector.selectedKeys();
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+ for (SelectionKey key : keys) {
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+ if (Thread.interrupted()) {
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+ return;
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+ }
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+ try {
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+ handleSelection(key);
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+ } catch (IOException | IllegalStateException e) {
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+ LOG.error("exception in selector", e);
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+ } finally {
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+ keysToRemove.add(key);
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+ }
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+ }
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+ keys.removeAll(keysToRemove);
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+ }
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+ } catch (ClosedSelectorException e) {
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+ return;
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+ } catch (Exception e) {
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+ LOG.error("error while selecting", e);
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+ }
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+ }
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+ }
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+
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+ /**
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+ * Checks if there is a valid port at
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+ * {@link Preferences#userNodeForPackage(Class)} for {@link Main} under the
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+ * given applicationKey, tries to connect to the port at the loopback
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+ * address and checks if the port identifies with the applicationKey.
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+ *
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+ * @param applicationKey
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+ * key used to load the port and check the identity of the
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+ * connection.
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+ * @return
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+ */
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+ public static Optional<RemoteInstance> getRemoteInstance(String applicationKey) {
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+ Optional<Integer> port = getSavedPort(applicationKey);
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+
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+ if (!port.isPresent()) {
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+ return Optional.empty();
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+ }
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+
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+ SocketChannel channel = null;
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+ boolean close = true;
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+ try {
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+ channel = SocketChannel.open();
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+ channel.configureBlocking(false);
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+ LOG.info("connecting to instance {}", port.get());
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+ channel.connect(new InetSocketAddress(InetAddress.getLoopbackAddress(), port.get()));
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+
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+ SocketChannel fChannel = channel;
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+ if (!TimeoutTask.attempt(t -> fChannel.finishConnect(), 1000, 10)) {
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+ return Optional.empty();
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+ }
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+
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+ LOG.info("connected to instance {}", port.get());
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+
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+ final byte[] bytes = applicationKey.getBytes();
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+ ByteBuffer buf = ByteBuffer.allocate(bytes.length);
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+ tryFill(channel, buf, 1000);
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+ if (buf.hasRemaining()) {
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+ return Optional.empty();
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+ }
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+
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+ buf.flip();
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+
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+ for (int i = 0; i < bytes.length; i++) {
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+ if (buf.get() != bytes[i]) {
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+ return Optional.empty();
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+ }
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+ }
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+
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+ close = false;
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+ return Optional.of(new RemoteInstance(channel));
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+ } catch (Exception e) {
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+ return Optional.empty();
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+ } finally {
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+ if (close) {
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+ IOUtils.closeQuietly(channel);
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+ }
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+ }
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+ }
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+
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+ static Optional<Integer> getSavedPort(String applicationKey) {
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+ int port = Preferences.userNodeForPackage(Main.class).getInt(applicationKey, -1);
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+
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+ if (port == -1) {
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+ LOG.info("no running instance found");
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+ return Optional.empty();
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+ }
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+
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+ return Optional.of(port);
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+ }
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+
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+ /**
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+ * Creates a server socket on a free port and saves the port in
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+ * {@link Preferences#userNodeForPackage(Class)} for {@link Main} under the
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+ * given applicationKey.
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+ *
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+ * @param applicationKey
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+ * key used to save the port and identify upon connection.
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+ * @param exec
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+ * the task which is submitted is interruptable.
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+ * @return
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+ * @throws IOException
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+ */
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+ public static LocalInstance startLocalInstance(String applicationKey, ExecutorService exec) throws IOException {
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+ final ServerSocketChannel channel = ServerSocketChannel.open();
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+ channel.configureBlocking(false);
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+ channel.bind(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0));
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+
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+ final int port = ((InetSocketAddress) channel.getLocalAddress()).getPort();
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+ Preferences.userNodeForPackage(Main.class).putInt(applicationKey, port);
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+ LOG.info("InstanceManager bound to port {}", port);
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+
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+ Selector selector = Selector.open();
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+ channel.register(selector, SelectionKey.OP_ACCEPT);
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+
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+ LocalInstance instance = new LocalInstance(applicationKey, channel, selector);
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+
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+ exec.submit(() -> {
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+ try {
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+ instance.port = ((InetSocketAddress) channel.getLocalAddress()).getPort();
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+ } catch (IOException e) {
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+
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+ }
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+ instance.selectionLoop();
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+ });
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+
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+ return instance;
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+ }
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+
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+ /**
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+ * tries to fill the given buffer for the given time
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+ *
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+ * @param channel
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+ * @param buf
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+ * @param timeout
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+ * @throws ClosedChannelException
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+ * @throws IOException
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+ */
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+ public static <T extends SelectableChannel & ReadableByteChannel> void tryFill(T channel, final ByteBuffer buf, int timeout) throws IOException {
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+ if (channel.isBlocking()) {
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+ throw new IllegalStateException("Channel is in blocking mode.");
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+ }
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+
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+ try (Selector selector = Selector.open()) {
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+ channel.register(selector, SelectionKey.OP_READ);
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+
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+ TimeoutTask.attempt(remainingTime -> {
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+ if (!buf.hasRemaining()) {
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+ return true;
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+ }
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+ if (selector.select(remainingTime) > 0) {
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+ if (channel.read(buf) < 0) {
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+ return true;
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+ }
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+ }
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+ return !buf.hasRemaining();
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+ }, timeout, 1);
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+ }
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+ }
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+}
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Sebastian Stenzel