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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.handler.codec.http;

import static org.jboss.netty.channel.Channels.*;
import static org.jboss.netty.handler.codec.http.HttpHeaders.*;

import java.util.List;
import java.util.Map.Entry;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.buffer.CompositeChannelBuffer;
import org.jboss.netty.channel.ChannelHandler;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.LifeCycleAwareChannelHandler;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
import org.jboss.netty.handler.codec.frame.TooLongFrameException;
import org.jboss.netty.util.CharsetUtil;

/**
 * A {@link ChannelHandler} that aggregates an {@link HttpMessage}
 * and its following {@link HttpChunk}s into a single {@link HttpMessage} with
 * no following {@link HttpChunk}s.  It is useful when you don't want to take
 * care of HTTP messages whose transfer encoding is 'chunked'.  Insert this
 * handler after {@link HttpMessageDecoder} in the {@link ChannelPipeline}:
 *  * {@link ChannelPipeline} p = ...;
 * ...
 * p.addLast("decoder", new {@link HttpRequestDecoder}());
 * p.addLast("aggregator", new {@link HttpChunkAggregator}(1048576));
 * ...
 * p.addLast("encoder", new {@link HttpResponseEncoder}());
 * p.addLast("handler", new HttpRequestHandler());
 * 
 * @apiviz.landmark
 * @apiviz.has org.jboss.netty.handler.codec.http.HttpChunk oneway - - filters out
 */
public class HttpChunkAggregator extends SimpleChannelUpstreamHandler implements LifeCycleAwareChannelHandler {
    public static final int DEFAULT_MAX_COMPOSITEBUFFER_COMPONENTS = 1024;

    private static final ChannelBuffer CONTINUE = ChannelBuffers.copiedBuffer(
            "HTTP/1.1 100 Continue\r\n\r\n", CharsetUtil.US_ASCII);

    private final int maxContentLength;
    private HttpMessage currentMessage;
    private boolean tooLongFrameFound;
    private ChannelHandlerContext ctx;

    private int maxCumulationBufferComponents = DEFAULT_MAX_COMPOSITEBUFFER_COMPONENTS;

    /**
     * Creates a new instance.
     *
     * @param maxContentLength
     *        the maximum length of the aggregated content.
     *        If the length of the aggregated content exceeds this value,
     *        a {@link TooLongFrameException} will be raised.
     */
    public HttpChunkAggregator(int maxContentLength) {
        if (maxContentLength <= 0) {
            throw new IllegalArgumentException(
                    "maxContentLength must be a positive integer: " +
                    maxContentLength);
        }
        this.maxContentLength = maxContentLength;
    }

    /**
     * Returns the maximum number of components in the cumulation buffer.  If the number of
     * the components in the cumulation buffer exceeds this value, the components of the
     * cumulation buffer are consolidated into a single component, involving memory copies.
     * The default value of this property is {@link #DEFAULT_MAX_COMPOSITEBUFFER_COMPONENTS}.
     */
    public final int getMaxCumulationBufferComponents() {
        return maxCumulationBufferComponents;
    }

    /**
     * Sets the maximum number of components in the cumulation buffer.  If the number of
     * the components in the cumulation buffer exceeds this value, the components of the
     * cumulation buffer are consolidated into a single component, involving memory copies.
     * The default value of this property is {@link #DEFAULT_MAX_COMPOSITEBUFFER_COMPONENTS}
     * and its minimum allowed value is {@code 2}.
     */
    public final void setMaxCumulationBufferComponents(int maxCumulationBufferComponents) {
        if (maxCumulationBufferComponents < 2) {
            throw new IllegalArgumentException(
                    "maxCumulationBufferComponents: " + maxCumulationBufferComponents +
                    " (expected: >= 2)");
        }

        if (ctx == null) {
            this.maxCumulationBufferComponents = maxCumulationBufferComponents;
        } else {
            throw new IllegalStateException(
                    "decoder properties cannot be changed once the decoder is added to a pipeline.");
        }
    }

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e)
            throws Exception {

        Object msg = e.getMessage();
        HttpMessage currentMessage = this.currentMessage;

        if (msg instanceof HttpMessage) {
            HttpMessage m = (HttpMessage) msg;
            tooLongFrameFound = false;

            // Handle the 'Expect: 100-continue' header if necessary.
            // TODO: Respond with 413 Request Entity Too Large
            //   and discard the traffic or close the connection.
            //       No need to notify the upstream handlers - just log.
            //       If decoding a response, just throw an exception.
            if (is100ContinueExpected(m)) {
                write(ctx, succeededFuture(ctx.getChannel()), CONTINUE.duplicate());
            }

            if (m.isChunked()) {
                // A chunked message - remove 'Transfer-Encoding' header,
                // initialize the cumulative buffer, and wait for incoming chunks.
                HttpCodecUtil.removeTransferEncodingChunked(m);
                m.setChunked(false);
                this.currentMessage = m;
            } else {
                // Not a chunked message - pass through.
                this.currentMessage = null;
                ctx.sendUpstream(e);
            }
        } else if (msg instanceof HttpChunk) {
            // Sanity check
            if (currentMessage == null) {
                throw new IllegalStateException(
                        "received " + HttpChunk.class.getSimpleName() +
                        " without " + HttpMessage.class.getSimpleName());
            }
            HttpChunk chunk = (HttpChunk) msg;

            if (tooLongFrameFound) {
                if (chunk.isLast()) {
                    this.currentMessage = null;
                }
                return;
            }

            // Merge the received chunk into the content of the current message.
            ChannelBuffer content = currentMessage.getContent();

            if (content.readableBytes() > maxContentLength - chunk.getContent().readableBytes()) {
                tooLongFrameFound = true;

                throw new TooLongFrameException(
                        "HTTP content length exceeded " + maxContentLength +
                        " bytes.");
            }

            // Append the content of the chunk
            appendToCumulation(chunk.getContent());

            if (chunk.isLast()) {
                this.currentMessage = null;

                // Merge trailing headers into the message.
                if (chunk instanceof HttpChunkTrailer) {
                    HttpChunkTrailer trailer = (HttpChunkTrailer) chunk;
                    for (Entry header: trailer.trailingHeaders()) {
                        currentMessage.headers().set(header.getKey(), header.getValue());
                    }
                }

                // Set the 'Content-Length' header.
                currentMessage.headers().set(
                        HttpHeaders.Names.CONTENT_LENGTH,
                        String.valueOf(content.readableBytes()));

                // All done - generate the event.
                fireMessageReceived(ctx, currentMessage, e.getRemoteAddress());
            }
        } else {
            // Neither HttpMessage or HttpChunk
            ctx.sendUpstream(e);
        }
    }

    protected void appendToCumulation(ChannelBuffer input) {
        ChannelBuffer cumulation = currentMessage.getContent();
        if (cumulation instanceof CompositeChannelBuffer) {
            // Make sure the resulting cumulation buffer has no more than the configured components.
            CompositeChannelBuffer composite = (CompositeChannelBuffer) cumulation;
            if (composite.numComponents() >= maxCumulationBufferComponents) {
                currentMessage.setContent(ChannelBuffers.wrappedBuffer(composite.copy(), input));
            } else {
                List decomposed = composite.decompose(0, composite.readableBytes());
                ChannelBuffer[] buffers = decomposed.toArray(new ChannelBuffer[decomposed.size() + 1]);
                buffers[buffers.length - 1] = input;

                currentMessage.setContent(ChannelBuffers.wrappedBuffer(buffers));
            }
        } else {
            currentMessage.setContent(ChannelBuffers.wrappedBuffer(cumulation, input));
        }
    }

    public void beforeAdd(ChannelHandlerContext ctx) throws Exception {
        this.ctx = ctx;
    }

    public void afterAdd(ChannelHandlerContext ctx) throws Exception {
        // noop
    }

    public void beforeRemove(ChannelHandlerContext ctx) throws Exception {
        // noop
    }

    public void afterRemove(ChannelHandlerContext ctx) throws Exception {
        // noop
    }
}