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/*
* Copyright (c) 2011 jMonkeyEngine
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of 'jMonkeyEngine' nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.jme3.network.base;
import com.jme3.network.Message;
import com.jme3.network.serializing.Serializer;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.LinkedList;
/**
* Consolidates the conversion of messages to/from byte buffers
* and provides a rolling message buffer. ByteBuffers can be
* pushed in and messages will be extracted, accumulated, and
* available for retrieval. This is not thread safe and is meant
* to be used within a single message processing thread.
*
* <p>The protocol is based on a simple length + data format
* where two bytes represent the (short) length of the data
* and the rest is the raw data for the Serializers class.</p>
*
* @version $Revision: 8843 $
* @author Paul Speed
*/
public class MessageProtocol
{
private LinkedList<Message> messages = new LinkedList<Message>();
private ByteBuffer current;
private int size;
private Byte carry;
/**
* Converts a message to a ByteBuffer using the Serializer
* and the (short length) + data protocol. If target is null
* then a 32k byte buffer will be created and filled.
*/
public static ByteBuffer messageToBuffer( Message message, ByteBuffer target )
{
// Could let the caller pass their own in
ByteBuffer buffer = target == null ? ByteBuffer.allocate( 32767 + 2 ) : target;
try {
buffer.position( 2 );
Serializer.writeClassAndObject( buffer, message );
buffer.flip();
short dataLength = (short)(buffer.remaining() - 2);
buffer.putShort( dataLength );
buffer.position( 0 );
return buffer;
} catch( IOException e ) {
throw new RuntimeException( "Error serializing message", e );
}
}
/**
* Retrieves and removes an extracted message from the accumulated buffer
* or returns null if there are no more messages.
*/
public Message getMessage()
{
if( messages.isEmpty() ) {
return null;
}
return messages.removeFirst();
}
/**
* Adds the specified buffer, extracting the contained messages
* and making them available to getMessage(). The left over
* data is buffered to be combined with future data.
&
* @return The total number of queued messages after this call.
*/
public int addBuffer( ByteBuffer buffer )
{
// push the data from the buffer into as
// many messages as we can
while( buffer.remaining() > 0 ) {
if( current == null ) {
// If we have a left over carry then we need to
// do manual processing to get the short value
if( carry != null ) {
byte high = carry;
byte low = buffer.get();
size = (high & 0xff) << 8 | (low & 0xff);
carry = null;
}
else if( buffer.remaining() < 2 ) {
// It's possible that the supplied buffer only has one
// byte in it... and in that case we will get an underflow
// when attempting to read the short below.
// It has to be 1 or we'd never get here... but one
// isn't enough so we stash it away.
carry = buffer.get();
break;
} else {
// We are not currently reading an object so
// grab the size.
// Note: this is somewhat limiting... int would
// be better.
size = buffer.getShort();
}
// Allocate the buffer into which we'll feed the
// data as we get it
current = ByteBuffer.allocate(size);
}
if( current.remaining() <= buffer.remaining() ) {
// We have at least one complete object so
// copy what we can into current, create a message,
// and then continue pulling from buffer.
// Artificially set the limit so we don't overflow
int extra = buffer.remaining() - current.remaining();
buffer.limit( buffer.position() + current.remaining() );
// Now copy the data
current.put( buffer );
current.flip();
// Now set the limit back to a good value
buffer.limit( buffer.position() + extra );
createMessage( current );
current = null;
} else {
// Not yet a complete object so just copy what we have
current.put( buffer );
}
}
return messages.size();
}
/**
* Creates a message from the properly sized byte buffer
* and adds it to the messages queue.
*/
protected void createMessage( ByteBuffer buffer )
{
try {
Object obj = Serializer.readClassAndObject( buffer );
Message m = (Message)obj;
messages.add(m);
} catch( IOException e ) {
throw new RuntimeException( "Error deserializing object", e );
}
}
}
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