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    1   /*
    2    * Copyright 2001-2005 The Apache Software Foundation
    3    *
    4    * Licensed under the Apache License, Version 2.0 (the "License");
    5    * you may not use this file except in compliance with the License.
    6    * You may obtain a copy of the License at
    7    *
    8    *     http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  package org.apache.commons.net.tftp;
    17
    18  import java.net.DatagramPacket;
    19  import java.net.InetAddress;
    20
    21  /****
    22   * A final class derived from TFTPPacket definiing the TFTP Acknowledgement
    23   * packet type.
    24   * <p>
    25   * Details regarding the TFTP protocol and the format of TFTP packets can
    26   * be found in RFC 783.  But the point of these classes is to keep you
    27   * from having to worry about the internals.  Additionally, only very
    28   * few people should have to care about any of the TFTPPacket classes
    29   * or derived classes.  Almost all users should only be concerned with the
    30   * {@link org.apache.commons.net.tftp.TFTPClient} class
    31   * {@link org.apache.commons.net.tftp.TFTPClient#receiveFile receiveFile()}
    32   * and
    33   * {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()}
    34   * methods.
    35   * <p>
    36   * <p>
    37   * @author Daniel F. Savarese
    38   * @see TFTPPacket
    39   * @see TFTPPacketException
    40   * @see TFTP
    41   ***/
    42
    43  public final class TFTPAckPacket extends TFTPPacket
    44  {
    45      /**** The block number being acknowledged by the packet. ***/
    46      int _blockNumber;
    47
    48      /****
    49       * Creates an acknowledgment packet to be sent to a host at a given port
    50       * acknowledging receipt of a block.
    51       * <p>
    52       * @param destination  The host to which the packet is going to be sent.
    53       * @param port  The port to which the packet is going to be sent.
    54       * @param blockNumber  The block number being acknowledged.
    55       ***/
    56      public TFTPAckPacket(InetAddress destination, int port, int blockNumber)
    57      {
    58          super(TFTPPacket.ACKNOWLEDGEMENT, destination, port);
    59          _blockNumber = blockNumber;
    60      }
    61
    62      /****
    63       * Creates an acknowledgement packet based from a received
    64       * datagram.  Assumes the datagram is at least length 4, else an
    65       * ArrayIndexOutOfBoundsException may be thrown.
    66       * <p>
    67       * @param datagram  The datagram containing the received acknowledgement.
    68       * @throws TFTPPacketException  If the datagram isn't a valid TFTP
    69       *         acknowledgement packet.
    70       ***/
    71      TFTPAckPacket(DatagramPacket datagram) throws TFTPPacketException
    72      {
    73          super(TFTPPacket.ACKNOWLEDGEMENT, datagram.getAddress(),
    74                datagram.getPort());
    75          byte[] data;
    76
    77          data = datagram.getData();
    78
    79          if (getType() != data[1])
    80              throw new TFTPPacketException("TFTP operator code does not match type.");
    81
    82          _blockNumber = (((data[2] & 0xff) << 8) | (data[3] & 0xff));
    83      }
    84
    85      /****
    86       * This is a method only available within the package for
    87       * implementing efficient datagram transport by elminating buffering.
    88       * It takes a datagram as an argument, and a byte buffer in which
    89       * to store the raw datagram data.  Inside the method, the data
    90       * is set as the datagram's data and the datagram returned.
    91       * <p>
    92       * @param datagram  The datagram to create.
    93       * @param data The buffer to store the packet and to use in the datagram.
    94       * @return The datagram argument.
    95       ***/
    96      DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
    97      {
    98          data[0] = 0;
    99          data[1] = (byte)_type;
    100         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
    101         data[3] = (byte)(_blockNumber & 0xff);
    102
    103         datagram.setAddress(_address);
    104         datagram.setPort(_port);
    105         datagram.setData(data);
    106         datagram.setLength(4);
    107
    108         return datagram;
    109     }
    110
    111
    112     /****
    113      * Creates a UDP datagram containing all the TFTP
    114      * acknowledgement packet data in the proper format.
    115      * This is a method exposed to the programmer in case he
    116      * wants to implement his own TFTP client instead of using
    117      * the {@link org.apache.commons.net.tftp.TFTPClient}
    118      * class.  Under normal circumstances, you should not have a need to call this
    119      * method.
    120      * <p>
    121      * @return A UDP datagram containing the TFTP acknowledgement packet.
    122      ***/
    123     public DatagramPacket newDatagram()
    124     {
    125         byte[] data;
    126
    127         data = new byte[4];
    128         data[0] = 0;
    129         data[1] = (byte)_type;
    130         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
    131         data[3] = (byte)(_blockNumber & 0xff);
    132
    133         return new DatagramPacket(data, data.length, _address, _port);
    134     }
    135
    136
    137     /****
    138      * Returns the block number of the acknowledgement.
    139      * <p>
    140      * @return The block number of the acknowledgement.
    141      ***/
    142     public int getBlockNumber()
    143     {
    144         return _blockNumber;
    145     }
    146
    147
    148     /**** Sets the block number of the acknowledgement.  ***/
    149     public void setBlockNumber(int blockNumber)
    150     {
    151         _blockNumber = blockNumber;
    152     }
    153 }
    154