header.java

jxme的一些相关程序,主要是手机上程序开发以及手机和计算机通信的一些程序资料,程序编译需要Ant支持

/************************************************************************
 * $Id: Header.java,v 1.2 2002/03/04 21:42:57 echtcherbina Exp $
 *
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA"
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 SUN MICROSYSTEMS OR
 * ITS 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.
 *
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 *********************************************************************************/

package net.jxta.impl.endpoint.tcp;

import java.net.*;
import java.io.*;
import java.util.*;

import net.jxta.endpoint.*;
import net.jxta.impl.endpoint.*;

/***
 * This class implements the TCP Transport Protocol Header
 *
 * The format of the header is:
 *
 * 1 byte: type
 * 4 bytes: src IP
 * 2 bytes: src port
 * 4 bytes: size of packed (beside this header)
 * 1 byte: option
 * 4 bytes: packet id
 * 4 bytes: unused
 * Depending on the command, some of the fields may not be used. However,
 * the header is fixed: used fields are ignored, but transmitted. 
 */

public class Header {

    public byte          cmd;
    public byte[]        srcAddr;
    public int           srcPort;
    public int           size;
    public int           option;
    public int           packetId;
    public static int    length = 20; // This is bigger than what is needed

    // Cmds
    public static final int PROPAGATE = 1;
    public static final int UNICAST = 2;
/* FIXME: ACK and NACK are stated to be unused in the spec.  Is this 
 * still true?  If not, where are they used and for what?
 */
    public static final int ACK = 3;
    public static final int NACK = 4;

    // Cmds options
  /* FIXME: These need to be squared with spec.  Where are they used.
   */ 
    public static final int HANDCHECK = 1;
    public static final int NONBLOCKING = 2;


    public Header () {
	srcAddr = new byte [4];
    }

    /**
     * Utility methods for host to network (and vice versa) conversion
     * for unsigned long and short.
     */

    private static void htonl (int v, byte[] buffer, int offset) {

	buffer [offset]     = (byte) ((v & 0xff000000) >> 24);
	buffer [offset + 1] = (byte) ((v & 0x00ff0000) >> 16);
	buffer [offset + 2] = (byte) ((v & 0x0000ff00) >> 8);
	buffer [offset + 3] = (byte) (v & 0x000000ff);
    }

    private static void htons (int v, byte[] buffer, int offset) {

	buffer [offset]     = (byte) ((v & 0xff00) >> 8);
	buffer [offset + 1] = (byte) (v & 0x00ff);
    }

    private static int ntohl(byte[] buffer, int offset) {

	return ((((int) buffer [offset]) << 24) & 0xff000000) |
	       ((((int) buffer [offset + 1]) << 16) & 0xff0000) |
	       ((((int) buffer [offset + 2]) << 8) & 0xff00) |
	       (((int) buffer [offset + 3]) & 0xff);
    }

    private static int ntohs(byte[] buffer, int offset) {
	return ((((int) buffer [offset]) << 24) & 0xff000000) |
	       ((((int) buffer [offset + 1]) << 16) & 0xff0000) |
	       ((((int) buffer [offset + 2]) << 8) & 0xff00) |
	       (((int) buffer [offset + 3]) & 0xff);

    }

    public boolean initFromNetwork (byte[] buffer, int offset) {
        
	cmd = buffer [offset];
        if (cmd != PROPAGATE
            && cmd != UNICAST
            && cmd != ACK
            && cmd != NACK) return false;

	srcAddr [0] = buffer [offset + 1];
	srcAddr [1] = buffer [offset + 2];
	srcAddr [2] = buffer [offset + 3];
	srcAddr [3] = buffer [offset + 4];
	srcPort = ntohs (buffer, offset + 5);
	size = ntohl (buffer, offset + 7);
	option = buffer [offset + 11];
	packetId = ntohl (buffer, offset +12);
        return true;
    }


    public void buildForNetwork (byte[] buffer, int offset) {

	int tmpOffset = offset;
	buffer [tmpOffset++] = cmd;
	buffer [tmpOffset++] = srcAddr [0];
	buffer [tmpOffset++] = srcAddr [1];
	buffer [tmpOffset++] = srcAddr [2];
	buffer [tmpOffset++] = srcAddr [3];
	htons (srcPort, buffer, tmpOffset);
	tmpOffset += 2;
	htonl (size, buffer, tmpOffset);
	tmpOffset += 4;
	buffer [tmpOffset++] = (byte) option;
	htonl (packetId, buffer, tmpOffset);
	tmpOffset += 4;
    }

}