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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.socks;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.replay.ReplayingDecoder;
import org.jboss.netty.util.CharsetUtil;

/**
 * Decodes {@link ChannelBuffer}s into {@link SocksCmdResponse}.
 * Before returning SocksResponse decoder removes itself from pipeline.
 */
public class SocksCmdResponseDecoder extends ReplayingDecoder {
    private static final String name = "SOCKS_CMD_RESPONSE_DECODER";

    /**
     * @deprecated Will be removed at the next minor version bump.
     */
    @Deprecated
    public static String getName() {
        return name;
    }

    private SocksMessage.ProtocolVersion version;
    private int fieldLength;
    private SocksMessage.CmdStatus cmdStatus;
    private SocksMessage.AddressType addressType;
    private byte reserved;
    private String host;
    private int port;
    private SocksResponse msg = SocksCommonUtils.UNKNOWN_SOCKS_RESPONSE;

    public SocksCmdResponseDecoder() {
        super(State.CHECK_PROTOCOL_VERSION);
    }

    @Override
    protected Object decode(ChannelHandlerContext ctx, Channel channel,
                            ChannelBuffer buffer, State state) throws Exception {
        switch (state) {
            case CHECK_PROTOCOL_VERSION: {
                version = SocksMessage.ProtocolVersion.fromByte(buffer.readByte());
                if (version != SocksMessage.ProtocolVersion.SOCKS5) {
                    break;
                }
                checkpoint(State.READ_CMD_HEADER);
            }
            case READ_CMD_HEADER: {
                cmdStatus = SocksMessage.CmdStatus.fromByte(buffer.readByte());
                reserved = buffer.readByte();
                addressType = SocksMessage.AddressType.fromByte(buffer.readByte());
                checkpoint(State.READ_CMD_ADDRESS);
            }
            case READ_CMD_ADDRESS: {
                switch (addressType) {
                    case IPv4: {
                        host = SocksCommonUtils.intToIp(buffer.readInt());
                        port = buffer.readUnsignedShort();
                        msg = new SocksCmdResponse(cmdStatus, addressType);
                        break;
                    }
                    case DOMAIN: {
                        fieldLength = buffer.readByte();
                        host = buffer.readBytes(fieldLength).toString(CharsetUtil.US_ASCII);
                        port = buffer.readUnsignedShort();
                        msg = new SocksCmdResponse(cmdStatus, addressType);
                        break;
                    }
                    case IPv6: {
                        host = SocksCommonUtils.ipv6toStr(buffer.readBytes(16).array());
                        port = buffer.readUnsignedShort();
                        msg = new SocksCmdResponse(cmdStatus, addressType);
                        break;
                    }
                    case UNKNOWN:
                        break;
                }
            }
        }
        ctx.getPipeline().remove(this);
        return msg;
    }

    public enum State {
        CHECK_PROTOCOL_VERSION,
        READ_CMD_HEADER,
        READ_CMD_ADDRESS
    }
}