sender.java

用于传感器网络的节点操作系统 TinyOS 结构设计非常有意思

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 * Authors:  David Gay  <[e-mail]>
 *           Intel Research Berkeley Lab
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package net.tinyos.message;

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

/**
 * Sender class (send tinyos messages).<p>
 *
 * A sender class provides a simple interface built on Message for
 * sending tinyos messages to a SerialForwarder
 *
 * @version	1, 15 Jul 2002
 * @author	David Gay
 */
public class Sender {


    // If true, dump message contents that are sent
    private static final boolean VERBOSE = false;

    byte groupId;
    SerialStub sfw;
    TOSMsg packet;

    /**
     * Create a sender for group id gid talking to SerialForwarder forwarder
     * @param forwarder SerialForwarder with which we wish to send messages
     * @param gid group id to be placed in sent messages
     */
    public Sender(SerialStub forwarder, int gid) {
        if ((gid < 0) || (gid > 0xff)) {
	  throw new IllegalArgumentException("Cannot send messages to invalid group ID: "+gid);
	}
	groupId = (byte)(gid & 0xff);
	sfw = forwarder;
	packet = new TOSMsg(SerialForwarderStub.PACKET_SIZE);
    }

    /**
     * Send m to moteId via this Sender's SerialForwarder
     * @param moteId message destination
     * @param m message
     * @exception IOException thrown if message could not be sent
     */
    synchronized public void send(int moteId, Message m) throws IOException {
	int amType = m.amType();

	if (amType < 0) {
	    throw new IOException("unknown AM type for message " +
				  m.getClass().getName());
	}

	//  message header: destination, group id, and message type
	packet.set_addr(moteId);
	packet.set_group(groupId);
	packet.set_type((short)amType);
	// Set CRC to 1 in case we're going directly to a UART;
	packet.set_crc(1);
	byte[] data = m.dataGet();
	packet.set_length((short)data.length);
	if (data.length > MoteIF.maxMessageSize)
	    throw new IOException("message too big (" + data.length + " bytes)");
	packet.dataSet(data, 0, packet.offset_data(0), data.length);

	data = packet.dataGet();
	sfw.Write(data);
	if (VERBOSE) Dump.dump("sent", data);
    }
}