src/java/com/oroinc/net/tftp/TFTPRequestPacket.java

/***
 * $Id: TFTPRequestPacket.java,v 1.1 2002/04/03 01:04:39 brekke Exp $
 *
 * NetComponents Internet Protocol Library
 * Copyright (C) 1997-2002  Daniel F. Savarese
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library in the LICENSE file; if not, write
 * to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA  02111-1307  USA
 ***/

package com.oroinc.net.tftp;

import java.net.*;

/***
 * An abstract class derived from TFTPPacket definiing a TFTP Request
 * packet type.  It is subclassed by the 
 * <a href="com.oroinc.net.tftp.TFTPReadRequestPacket.html#_top_">
 * TFTPReadRequestPacket</a>  and
 * <a href="com.oroinc.net.tftp.TFTPWriteRequestPacket.html#_top_">
 * TFTPWriteRequestPacket</a> classes.
 * <p>
 * Details regarding the TFTP protocol and the format of TFTP packets can
 * be found in RFC 783.  But the point of these classes is to keep you
 * from having to worry about the internals.  Additionally, only very
 * few people should have to care about any of the TFTPPacket classes
 * or derived classes.  Almost all users should only be concerned with the
 * <a href="com.oroinc.net.tftp.TFTPClient.html#_top_">TFTPClient</a> class
 * <a href="com.oroinc.net.tftp.TFTPClient.html#receiveFile">receiveFile()</a>
 * and
 * <a href="com.oroinc.net.tftp.TFTPClient.html#sendFile">sendFile()</a>
 * methods.
 * <p>
 * <p>
 * @author Daniel F. Savarese
 * @see TFTPPacket
 * @see TFTPReadRequestPacket
 * @see TFTPWriteRequestPacket
 * @see TFTPPacketException
 * @see TFTP
 ***/

public abstract class TFTPRequestPacket extends TFTPPacket {
  /***
   * An array containing the string names of the transfer modes and indexed
   * by the transfer mode constants.
   ***/
  static final String[] _modeStrings = { "netascii", "octet" };

  /***
   * A null terminated byte array representation of the ascii names of the
   * transfer mode constants.  This is convenient for creating the TFTP
   * request packets.
   ***/
  static final byte[]  _modeBytes[] = {
    { (byte)'n', (byte)'e', (byte)'t', (byte)'a', (byte)'s', (byte)'c',
      (byte)'i', (byte)'i', 0 },
    { (byte)'o', (byte)'c', (byte)'t', (byte)'e', (byte)'t', 0 }
  };

  /*** The transfer mode of the request. ***/
  int _mode;

  /*** The filename of the request. ***/
  String _filename;

  /***
   * Creates a request packet of a given type to be sent to a host at a 
   * given port with a filename and transfer mode request.
   * <p>
   * @param destination  The host to which the packet is going to be sent.
   * @param port  The port to which the packet is going to be sent.
   * @param type The type of the request (either TFTPPacket.READ_REQUEST or
   *             TFTPPacket.WRITE_REQUEST).
   * @param filename The requested filename.
   * @param mode The requested transfer mode.  This should be on of the TFTP
   *        class MODE constants (e.g., TFTP.NETASCII_MODE).
   ***/
  TFTPRequestPacket(InetAddress destination, int port,
		    int type, String filename, int mode) {
    super(type, destination, port);

    _filename = filename;
    _mode     = mode;
  }

  /***
   * Creates a request packet of a given type based on a received
   * datagram.  Assumes the datagram is at least length 4, else an
   * ArrayIndexOutOfBoundsException may be thrown.
   * <p>
   * @param type The type of the request (either TFTPPacket.READ_REQUEST or
   *             TFTPPacket.WRITE_REQUEST).
   * @param datagram  The datagram containing the received request.
   * @throws TFTPPacketException  If the datagram isn't a valid TFTP
   *         request packet of the appropriate type.
   ***/
  TFTPRequestPacket(int type, DatagramPacket datagram)
       throws TFTPPacketException
  {
    super(type, datagram.getAddress(), datagram.getPort());

    byte[] data;
    int index, length;
    String mode;
    StringBuffer buffer;

    data = datagram.getData();

    if(getType() != data[1])
      throw new TFTPPacketException("TFTP operator code does not match type.");

    buffer = new StringBuffer();

    index  = 2;
    length = datagram.getLength();

    while(index < length && data[index] != 0) {
      buffer.append((char)data[index]);
      ++index;
    }

    _filename = buffer.toString();
    
    if(index >= length)
      throw new TFTPPacketException("Bad filename and mode format.");

    buffer.setLength(0);
    ++index; // need to advance beyond the end of string marker
    while(index < length && data[index] != 0) {
      buffer.append((char)data[index]);
      ++index;
    }

    mode = buffer.toString().toLowerCase();
    length = _modeStrings.length;

    for(index = 0; index < length; index++) {
      if(mode.equals(_modeStrings[index])) {
	_mode = index;
	break;
      }
    }

    if(index >= length) {
      throw new TFTPPacketException("Unrecognized TFTP transfer mode: " + mode);
      // May just want to default to binary mode instead of throwing
      // exception.
      //_mode = TFTP.OCTET_MODE;
    }
  }


  /***
   * This is a method only available within the package for
   * implementing efficient datagram transport by elminating buffering.
   * It takes a datagram as an argument, and a byte buffer in which 
   * to store the raw datagram data.  Inside the method, the data
   * is set as the datagram's data and the datagram returned.
   * <p>
   * @param datagram  The datagram to create.
   * @param data The buffer to store the packet and to use in the datagram.
   * @return The datagram argument.
   ***/
  final DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data) {
    int fileLength, modeLength;

    fileLength  = _filename.length();
    modeLength  = _modeBytes[_mode].length;

    data[0] = 0; data[1] = (byte)_type;
    System.arraycopy(_filename.getBytes(), 0, data, 2, fileLength);
    data[fileLength + 2] = 0;
    System.arraycopy(_modeBytes[_mode], 0, data, fileLength + 3,
		     modeLength);

    datagram.setAddress(_address);
    datagram.setPort(_port);
    datagram.setData(data);
    datagram.setLength(fileLength + modeLength + 4);

    return datagram;
  }

  /***
   * This is a method exposed to the programmer in case he
   * wants to implement his own TFTP client instead of using
   * the <a href="com.oroinc.net.tftp.TFTPClient.html#_top_">TFTPClient</a> 
   * class.  Under normal circumstances, you should not have a need to call
   * this method.  It creates a UDP datagram containing all the TFTP
   * request packet data in the proper format.
   * <p>
   * @return A UDP datagram containing the TFTP request packet.
   ***/
  public final DatagramPacket newDatagram() {
    int fileLength, modeLength;
    byte[] data;

    fileLength = _filename.length();
    modeLength = _modeBytes[_mode].length;

    data = new byte[fileLength + modeLength + 4];
    data[0] = 0; data[1] = (byte)_type;
    System.arraycopy(_filename.getBytes(), 0, data, 2, fileLength);
    data[fileLength + 2] = 0;
    System.arraycopy(_modeBytes[_mode], 0, data, fileLength + 3,
		     modeLength);

    return new DatagramPacket(data, data.length, _address, _port);
  }

  /***
   * Returns the transfer mode of the request.
   * <p>
   * @return The transfer mode of the request.
   ***/
  public final int getMode() { return _mode; }

  /***
   * Returns the requested filename.
   * <p>
   * @return The requested filename.
   ***/
  public final String getFilename() { return _filename; }
}