001/* 002 * Trident - A Multithreaded Server Alternative 003 * Copyright 2014 The TridentSDK Team 004 * 005 * Licensed under the Apache License, Version 2.0 (the "License"); 006 * you may not use this file except in compliance with the License. 007 * You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package net.tridentsdk.server.netty.packet; 019 020import io.netty.buffer.ByteBuf; 021import io.netty.buffer.Unpooled; 022import io.netty.channel.ChannelHandlerContext; 023import io.netty.handler.codec.ReplayingDecoder; 024import net.tridentsdk.server.TridentServer; 025import net.tridentsdk.server.netty.ClientConnection; 026import net.tridentsdk.server.netty.Codec; 027 028import java.util.List; 029import java.util.zip.Inflater; 030 031/** 032 * Decoder that decompresses (if needed) and reads the length of the packet data sent from the stream in the form 033 * of the byte buffer. 034 * 035 * <p>This is needed to interpret the data sent correctly, and make sure that the data maintains its transmission 036 * integrity. 037 * 038 * <p>Note this is not thread safe. It should only be used on one thread, or create a new instance for each 039 * channel.</p> 040 * 041 * @author The TridentSDK Team 042 */ 043public class PacketDecoder extends ReplayingDecoder<Void> { 044 045 private final Inflater inflater = new Inflater(); 046 private ClientConnection connection; 047 private int rawLength; 048 049 @Override 050 public void handlerAdded(ChannelHandlerContext context) { 051 this.connection = ClientConnection.connection(context); 052 } 053 054 @Override 055 protected void decode(ChannelHandlerContext context, ByteBuf buf, List<Object> objects) throws Exception { 056 boolean compressed = connection.isCompressionEnabled(); 057 int fullLength = -1; 058 059 if (compressed) { 060 fullLength = Codec.readVarInt32(buf); 061 } 062 063 this.rawLength = Codec.readVarInt32(buf); 064 065 if (rawLength == 0) 066 compressed = false; 067 068 if (!(compressed) || rawLength < TridentServer.instance().compressionThreshold()) { 069 ByteBuf data = buf.readBytes((fullLength == -1) ? rawLength : (fullLength - Codec.sizeOf(0))); 070 071 objects.add(new PacketData(data)); 072 return; 073 } 074 075 byte[] compressedData = new byte[buf.readableBytes()]; 076 byte[] decompressed = new byte[rawLength]; 077 078 buf.readBytes(compressedData); 079 inflater.setInput(compressedData); 080 081 inflater.inflate(decompressed); 082 objects.add(new PacketData(Unpooled.wrappedBuffer(decompressed))); 083 084 inflater.reset(); 085 } 086}