attachment.java

利用java实现的多人游戏的服务器系统

package com.hypefiend.javagamebook.common;

import com.hypefiend.javagamebook.common.GameEvent;
import java.nio.ByteBuffer;
import java.nio.BufferUnderflowException;
import java.net.InetAddress;

import org.apache.log4j.Logger;

/**
 * Attachment.java
 *
 * This class is used as the Key attachment for each channel registered
 * with the Selector.
 * It holds the temporary incoming data and checks the completeness 
 * of the header and payload
 *
 * @author <a href="mailto:[e-mail]">bret barker</a>
 * @version 1.0
 */
public class Attachment {
    /** number of bytes in the network event header */
    public static final int HEADER_SIZE = 12; 

    /** log4j logger */
    private static Logger log = Logger.getLogger("Attachment");

    /** unique id for this client */
    int clientId;
    /** size in bytes of the payload (GameEvent) */
    int payloadSize;
    /** hash code of the GameName this event should be routed to */
    public int gameNameHash;

    /** do we have a full header yet? */
    private boolean gotHeader;

    /** buffer used to hold data as it's read from the channel */
    public ByteBuffer readBuff; 

     /** temporary storage of the payload before it is read into an event  */
     public byte payload[];
    
    /** 
     * constructor. initiales the payload array and the read buffer 
     */
    public Attachment (){
	payload = new byte[Globals.MAX_EVENT_SIZE];
	readBuff = ByteBuffer.allocateDirect(Globals.NET_BUFFER_SIZE);
    }
     
    /** 
     * checks if a full event has been read
     * @return true if the event is ready, otherwise false
     */
    public boolean eventReady() throws IllegalArgumentException {
	if (checkHeader() && checkPayload())
	    return true;
	else
	    return false;
    }

    /**
     * reset the attachment to prepare for reading the next event
     */
    public void reset() {
	gotHeader = false;
    }

    /**
     * Checks if we have a full header yet 
     * @return true if the header is fully available, otherwise false
     */
    private boolean checkHeader() throws IllegalArgumentException {
	if (gotHeader) return true;
	if (readBuff.remaining() >= HEADER_SIZE) {
	    // read the header info
	    clientId = readBuff.getInt();
	    gameNameHash = readBuff.getInt();
	    payloadSize = readBuff.getInt();

	    // check bounds on the payload
	    if (payloadSize > Globals.MAX_EVENT_SIZE) 
		throw new IllegalArgumentException("Header specifies payload size (" + 
						   payloadSize + ") greater than MAX_EVENT_SIZE(" + 
						   Globals.MAX_EVENT_SIZE + ")");
	    gotHeader = true;
	    return true;
	}
	else {
	    return false;
	}
    }

    /** 
     * check for a complete payload
     */
    private boolean checkPayload() {
	if (readBuff.remaining() >= payloadSize) {
 	    try {
  		readBuff.get(payload, 0, payloadSize);
 	    }
 	    catch (BufferUnderflowException bue) {
 		log.error("buffer underflow", bue);
 	    }
	    return true;
	}
	else {
	    return false;
	}
    }
}// Attachment