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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.jboss.netty.channel.socket.nio;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBufferFactory;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelException;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ReceiveBufferSizePredictor;
import org.jboss.netty.util.ThreadNameDeterminer;

import java.io.IOException;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.concurrent.Executor;

import static org.jboss.netty.channel.Channels.*;

public class NioWorker extends AbstractNioWorker {

    private final SocketReceiveBufferAllocator recvBufferPool = new SocketReceiveBufferAllocator();

    public NioWorker(Executor executor) {
        super(executor);
    }

    public NioWorker(Executor executor, ThreadNameDeterminer determiner) {
        super(executor, determiner);
    }

    @Override
    protected boolean read(SelectionKey k) {
        final SocketChannel ch = (SocketChannel) k.channel();
        final NioSocketChannel channel = (NioSocketChannel) k.attachment();

        final ReceiveBufferSizePredictor predictor =
            channel.getConfig().getReceiveBufferSizePredictor();
        final int predictedRecvBufSize = predictor.nextReceiveBufferSize();
        final ChannelBufferFactory bufferFactory = channel.getConfig().getBufferFactory();

        int ret = 0;
        int readBytes = 0;
        boolean failure = true;

        ByteBuffer bb = recvBufferPool.get(predictedRecvBufSize).order(bufferFactory.getDefaultOrder());
        try {
            while ((ret = ch.read(bb)) > 0) {
                readBytes += ret;
                if (!bb.hasRemaining()) {
                    break;
                }
            }
            failure = false;
        } catch (ClosedChannelException e) {
            // Can happen, and does not need a user attention.
        } catch (Throwable t) {
            fireExceptionCaught(channel, t);
        }

        if (readBytes > 0) {
            bb.flip();

            final ChannelBuffer buffer = bufferFactory.getBuffer(readBytes);
            buffer.setBytes(0, bb);
            buffer.writerIndex(readBytes);

            // Update the predictor.
            predictor.previousReceiveBufferSize(readBytes);

            // Fire the event.
            fireMessageReceived(channel, buffer);
        }

        if (ret < 0 || failure) {
            k.cancel(); // Some JDK implementations run into an infinite loop without this.
            close(channel, succeededFuture(channel));
            return false;
        }

        return true;
    }

    @Override
    protected boolean scheduleWriteIfNecessary(final AbstractNioChannel channel) {
        final Thread currentThread = Thread.currentThread();
        final Thread workerThread = thread;
        if (currentThread != workerThread) {
            if (channel.writeTaskInTaskQueue.compareAndSet(false, true)) {
                registerTask(channel.writeTask);
            }

            return true;
        }

        return false;
    }

    @Override
    protected Runnable createRegisterTask(Channel channel, ChannelFuture future) {
        boolean server = !(channel instanceof NioClientSocketChannel);
        return new RegisterTask((NioSocketChannel) channel, future, server);
    }

    private final class RegisterTask implements Runnable {
        private final NioSocketChannel channel;
        private final ChannelFuture future;
        private final boolean server;

        RegisterTask(
                NioSocketChannel channel, ChannelFuture future, boolean server) {

            this.channel = channel;
            this.future = future;
            this.server = server;
        }

        public void run() {
            SocketAddress localAddress = channel.getLocalAddress();
            SocketAddress remoteAddress = channel.getRemoteAddress();

            if (localAddress == null || remoteAddress == null) {
                if (future != null) {
                    future.setFailure(new ClosedChannelException());
                }
                close(channel, succeededFuture(channel));
                return;
            }

            try {
                if (server) {
                    channel.channel.configureBlocking(false);
                }

                channel.channel.register(
                        selector, channel.getInternalInterestOps(), channel);

                if (future != null) {
                    channel.setConnected();
                    future.setSuccess();
                }

                if (server || !((NioClientSocketChannel) channel).boundManually) {
                    fireChannelBound(channel, localAddress);
                }
                fireChannelConnected(channel, remoteAddress);
            } catch (IOException e) {
                if (future != null) {
                    future.setFailure(e);
                }
                close(channel, succeededFuture(channel));
                if (!(e instanceof ClosedChannelException)) {
                    throw new ChannelException(
                            "Failed to register a socket to the selector.", e);
                }
            }
        }
    }

    @Override
    public void run() {
        super.run();
        recvBufferPool.releaseExternalResources();
    }
}