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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 Data
    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 TFTPDataPacket extends TFTPPacket
    44  {
    45      /**** The maximum number of bytes in a TFTP data packet (512) ***/
    46      public static final int MAX_DATA_LENGTH = 512;
    47
    48      /**** The minimum number of bytes in a TFTP data packet (0) ***/
    49      public static final int MIN_DATA_LENGTH = 0;
    50
    51      /**** The block number of the packet. ***/
    52      int _blockNumber;
    53
    54      /**** The length of the data. ***/
    55      int _length;
    56
    57      /**** The offset into the _data array at which the data begins. ***/
    58      int _offset;
    59
    60      /**** The data stored in the packet. ***/
    61      byte[] _data;
    62
    63      /****
    64       * Creates a data packet to be sent to a host at a given port
    65       * with a given block number.  The actual data to be sent is passed as
    66       * an array, an offset, and a length.  The offset is the offset into
    67       * the byte array where the data starts.  The length is the length of
    68       * the data.  If the length is greater than MAX_DATA_LENGTH, it is
    69       * truncated.
    70       * <p>
    71       * @param destination  The host to which the packet is going to be sent.
    72       * @param port  The port to which the packet is going to be sent.
    73       * @param blockNumber The block number of the data.
    74       * @param data The byte array containing the data.
    75       * @param offset The offset into the array where the data starts.
    76       * @param length The length of the data.
    77       ***/
    78      public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
    79                            byte[] data, int offset, int length)
    80      {
    81          super(TFTPPacket.DATA, destination, port);
    82
    83          _blockNumber = blockNumber;
    84          _data = data;
    85          _offset = offset;
    86
    87          if (length > MAX_DATA_LENGTH)
    88              _length = MAX_DATA_LENGTH;
    89          else
    90              _length = length;
    91      }
    92
    93      public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
    94                            byte[] data)
    95      {
    96          this(destination, port, blockNumber, data, 0, data.length);
    97      }
    98
    99
    100     /****
    101      * Creates a data packet based from a received
    102      * datagram.  Assumes the datagram is at least length 4, else an
    103      * ArrayIndexOutOfBoundsException may be thrown.
    104      * <p>
    105      * @param datagram  The datagram containing the received data.
    106      * @throws TFTPPacketException  If the datagram isn't a valid TFTP
    107      *         data packet.
    108      ***/
    109     TFTPDataPacket(DatagramPacket datagram) throws TFTPPacketException
    110     {
    111         super(TFTPPacket.DATA, datagram.getAddress(), datagram.getPort());
    112
    113         _data = datagram.getData();
    114         _offset = 4;
    115
    116         if (getType() != _data[1])
    117             throw new TFTPPacketException("TFTP operator code does not match type.");
    118
    119         _blockNumber = (((_data[2] & 0xff) << 8) | (_data[3] & 0xff));
    120
    121         _length = datagram.getLength() - 4;
    122
    123         if (_length > MAX_DATA_LENGTH)
    124             _length = MAX_DATA_LENGTH;
    125     }
    126
    127     /****
    128      * This is a method only available within the package for
    129      * implementing efficient datagram transport by elminating buffering.
    130      * It takes a datagram as an argument, and a byte buffer in which
    131      * to store the raw datagram data.  Inside the method, the data
    132      * is set as the datagram's data and the datagram returned.
    133      * <p>
    134      * @param datagram  The datagram to create.
    135      * @param data The buffer to store the packet and to use in the datagram.
    136      * @return The datagram argument.
    137      ***/
    138     DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
    139     {
    140         data[0] = 0;
    141         data[1] = (byte)_type;
    142         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
    143         data[3] = (byte)(_blockNumber & 0xff);
    144
    145         // Doublecheck we're not the same
    146         if (data != _data)
    147             System.arraycopy(_data, _offset, data, 4, _length);
    148
    149         datagram.setAddress(_address);
    150         datagram.setPort(_port);
    151         datagram.setData(data);
    152         datagram.setLength(_length + 4);
    153
    154         return datagram;
    155     }
    156
    157     /****
    158      * Creates a UDP datagram containing all the TFTP
    159      * data packet data in the proper format.
    160      * This is a method exposed to the programmer in case he
    161      * wants to implement his own TFTP client instead of using
    162      * the {@link org.apache.commons.net.tftp.TFTPClient}
    163      * class.
    164      * Under normal circumstances, you should not have a need to call this
    165      * method.
    166      * <p>
    167      * @return A UDP datagram containing the TFTP data packet.
    168      ***/
    169     public DatagramPacket newDatagram()
    170     {
    171         byte[] data;
    172
    173         data = new byte[_length + 4];
    174         data[0] = 0;
    175         data[1] = (byte)_type;
    176         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
    177         data[3] = (byte)(_blockNumber & 0xff);
    178
    179         System.arraycopy(_data, _offset, data, 4, _length);
    180
    181         return new DatagramPacket(data, _length + 4, _address, _port);
    182     }
    183
    184     /****
    185      * Returns the block number of the data packet.
    186      * <p>
    187      * @return The block number of the data packet.
    188      ***/
    189     public int getBlockNumber()
    190     {
    191         return _blockNumber;
    192     }
    193
    194     /**** Sets the block number of the data packet.  ***/
    195     public void setBlockNumber(int blockNumber)
    196     {
    197         _blockNumber = blockNumber;
    198     }
    199
    200     /****
    201      * Sets the data for the data packet.
    202      * <p>
    203      * @param data The byte array containing the data.
    204      * @param offset The offset into the array where the data starts.
    205      * @param length The length of the data.
    206      ***/
    207     public void setData(byte[] data, int offset, int length)
    208     {
    209         _data = data;
    210         _offset = offset;
    211         _length = length;
    212
    213         if (length > MAX_DATA_LENGTH)
    214             _length = MAX_DATA_LENGTH;
    215         else
    216             _length = length;
    217     }
    218
    219     /****
    220      * Returns the length of the data part of the data packet.
    221      * <p>
    222      * @return The length of the data part of the data packet.
    223      ***/
    224     public int getDataLength()
    225     {
    226         return _length;
    227     }
    228
    229     /****
    230      * Returns the offset into the byte array where the packet data actually
    231      * starts.
    232      * <p>
    233      * @return The offset into the byte array where the packet data actually
    234      *         starts.
    235      ***/
    236     public int getDataOffset()
    237     {
    238         return _offset;
    239     }
    240
    241     /****
    242      * Returns the byte array containing the packet data.
    243      * <p>
    244      * @return The byte array containing the packet data.
    245      ***/
    246     public byte[] getData()
    247     {
    248         return _data;
    249     }
    250 }