1 /* 2 * Copyright (c) 2011 jMonkeyEngine 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are 7 * met: 8 * 9 * * Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 12 * * Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * * Neither the name of 'jMonkeyEngine' nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 22 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 23 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 24 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 25 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 26 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 27 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 28 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 29 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 30 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 package com.jme3.network.base; 34 35 import com.jme3.network.Message; 36 import com.jme3.network.serializing.Serializer; 37 import java.io.IOException; 38 import java.nio.ByteBuffer; 39 import java.util.LinkedList; 40 41 /** 42 * Consolidates the conversion of messages to/from byte buffers 43 * and provides a rolling message buffer. ByteBuffers can be 44 * pushed in and messages will be extracted, accumulated, and 45 * available for retrieval. This is not thread safe and is meant 46 * to be used within a single message processing thread. 47 * 48 * <p>The protocol is based on a simple length + data format 49 * where two bytes represent the (short) length of the data 50 * and the rest is the raw data for the Serializers class.</p> 51 * 52 * @version $Revision: 8843 $ 53 * @author Paul Speed 54 */ 55 public class MessageProtocol 56 { 57 private LinkedList<Message> messages = new LinkedList<Message>(); 58 private ByteBuffer current; 59 private int size; 60 private Byte carry; 61 62 /** 63 * Converts a message to a ByteBuffer using the Serializer 64 * and the (short length) + data protocol. If target is null 65 * then a 32k byte buffer will be created and filled. 66 */ messageToBuffer( Message message, ByteBuffer target )67 public static ByteBuffer messageToBuffer( Message message, ByteBuffer target ) 68 { 69 // Could let the caller pass their own in 70 ByteBuffer buffer = target == null ? ByteBuffer.allocate( 32767 + 2 ) : target; 71 72 try { 73 buffer.position( 2 ); 74 Serializer.writeClassAndObject( buffer, message ); 75 buffer.flip(); 76 short dataLength = (short)(buffer.remaining() - 2); 77 buffer.putShort( dataLength ); 78 buffer.position( 0 ); 79 80 return buffer; 81 } catch( IOException e ) { 82 throw new RuntimeException( "Error serializing message", e ); 83 } 84 } 85 86 /** 87 * Retrieves and removes an extracted message from the accumulated buffer 88 * or returns null if there are no more messages. 89 */ getMessage()90 public Message getMessage() 91 { 92 if( messages.isEmpty() ) { 93 return null; 94 } 95 96 return messages.removeFirst(); 97 } 98 99 /** 100 * Adds the specified buffer, extracting the contained messages 101 * and making them available to getMessage(). The left over 102 * data is buffered to be combined with future data. 103 & 104 * @return The total number of queued messages after this call. 105 */ addBuffer( ByteBuffer buffer )106 public int addBuffer( ByteBuffer buffer ) 107 { 108 // push the data from the buffer into as 109 // many messages as we can 110 while( buffer.remaining() > 0 ) { 111 112 if( current == null ) { 113 114 // If we have a left over carry then we need to 115 // do manual processing to get the short value 116 if( carry != null ) { 117 byte high = carry; 118 byte low = buffer.get(); 119 120 size = (high & 0xff) << 8 | (low & 0xff); 121 carry = null; 122 } 123 else if( buffer.remaining() < 2 ) { 124 // It's possible that the supplied buffer only has one 125 // byte in it... and in that case we will get an underflow 126 // when attempting to read the short below. 127 128 // It has to be 1 or we'd never get here... but one 129 // isn't enough so we stash it away. 130 carry = buffer.get(); 131 break; 132 } else { 133 // We are not currently reading an object so 134 // grab the size. 135 // Note: this is somewhat limiting... int would 136 // be better. 137 size = buffer.getShort(); 138 } 139 140 // Allocate the buffer into which we'll feed the 141 // data as we get it 142 current = ByteBuffer.allocate(size); 143 } 144 145 if( current.remaining() <= buffer.remaining() ) { 146 // We have at least one complete object so 147 // copy what we can into current, create a message, 148 // and then continue pulling from buffer. 149 150 // Artificially set the limit so we don't overflow 151 int extra = buffer.remaining() - current.remaining(); 152 buffer.limit( buffer.position() + current.remaining() ); 153 154 // Now copy the data 155 current.put( buffer ); 156 current.flip(); 157 158 // Now set the limit back to a good value 159 buffer.limit( buffer.position() + extra ); 160 161 createMessage( current ); 162 163 current = null; 164 } else { 165 166 // Not yet a complete object so just copy what we have 167 current.put( buffer ); 168 } 169 } 170 171 return messages.size(); 172 } 173 174 /** 175 * Creates a message from the properly sized byte buffer 176 * and adds it to the messages queue. 177 */ createMessage( ByteBuffer buffer )178 protected void createMessage( ByteBuffer buffer ) 179 { 180 try { 181 Object obj = Serializer.readClassAndObject( buffer ); 182 Message m = (Message)obj; 183 messages.add(m); 184 } catch( IOException e ) { 185 throw new RuntimeException( "Error deserializing object", e ); 186 } 187 } 188 } 189 190 191 192