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    1   package org.apache.commons.net.tftp;
    2
    3   /* ====================================================================
    4    * The Apache Software License, Version 1.1
    5    *
    6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
    7    * reserved.
    8    *
    9    * Redistribution and use in source and binary forms, with or without
    10   * modification, are permitted provided that the following conditions
    11   * are met:
    12   *
    13   * 1. Redistributions of source code must retain the above copyright
    14   *    notice, this list of conditions and the following disclaimer.
    15   *
    16   * 2. Redistributions in binary form must reproduce the above copyright
    17   *    notice, this list of conditions and the following disclaimer in
    18   *    the documentation and/or other materials provided with the
    19   *    distribution.
    20   *
    21   * 3. The end-user documentation included with the redistribution,
    22   *    if any, must include the following acknowledgment:
    23   *       "This product includes software developed by the
    24   *        Apache Software Foundation (http://www.apache.org/)."
    25   *    Alternately, this acknowledgment may appear in the software itself,
    26   *    if and wherever such third-party acknowledgments normally appear.
    27   *
    28   * 4. The names "Apache" and "Apache Software Foundation" and
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    30   *    derived from this software without prior written permission. For
    31   *    written permission, please contact apache@apache.org.
    32   *
    33   * 5. Products derived from this software may not be called "Apache",
    34   *    nor may "Apache" appear in their name, without
    35   *    prior written permission of the Apache Software Foundation.
    36   *
    37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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    41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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    49   * ====================================================================
    50   *
    51   * This software consists of voluntary contributions made by many
    52   * individuals on behalf of the Apache Software Foundation.  For more
    53   * information on the Apache Software Foundation, please see
    54   * <http://www.apache.org/>;.
    55   */
    56
    57  import java.net.DatagramPacket;
    58  import java.net.InetAddress;
    59
    60  /****
    61   * A final class derived from TFTPPacket definiing the TFTP Acknowledgement
    62   * packet type.
    63   * <p>
    64   * Details regarding the TFTP protocol and the format of TFTP packets can
    65   * be found in RFC 783.  But the point of these classes is to keep you
    66   * from having to worry about the internals.  Additionally, only very
    67   * few people should have to care about any of the TFTPPacket classes
    68   * or derived classes.  Almost all users should only be concerned with the
    69   * <a href="org.apache.commons.net.tftp.TFTPClient.html#_top_">TFTPClient</a> class
    70   * <a href="org.apache.commons.net.tftp.TFTPClient.html#receiveFile">receiveFile()</a>
    71   * and
    72   * <a href="org.apache.commons.net.tftp.TFTPClient.html#sendFile">sendFile()</a>
    73   * methods.
    74   * <p>
    75   * <p>
    76   * @author Daniel F. Savarese
    77   * @see TFTPPacket
    78   * @see TFTPPacketException
    79   * @see TFTP
    80   ***/
    81
    82  public final class TFTPAckPacket extends TFTPPacket
    83  {
    84      /**** The block number being acknowledged by the packet. ***/
    85      int _blockNumber;
    86
    87      /****
    88       * Creates an acknowledgment packet to be sent to a host at a given port
    89       * acknowledging receipt of a block.
    90       * <p>
    91       * @param destination  The host to which the packet is going to be sent.
    92       * @param port  The port to which the packet is going to be sent.
    93       * @param blockNumber  The block number being acknowledged.
    94       ***/
    95      public TFTPAckPacket(InetAddress destination, int port, int blockNumber)
    96      {
    97          super(TFTPPacket.ACKNOWLEDGEMENT, destination, port);
    98          _blockNumber = blockNumber;
    99      }
    100
    101     /****
    102      * Creates an acknowledgement packet based from a received
    103      * datagram.  Assumes the datagram is at least length 4, else an
    104      * ArrayIndexOutOfBoundsException may be thrown.
    105      * <p>
    106      * @param datagram  The datagram containing the received acknowledgement.
    107      * @throws TFTPPacketException  If the datagram isn't a valid TFTP
    108      *         acknowledgement packet.
    109      ***/
    110     TFTPAckPacket(DatagramPacket datagram) throws TFTPPacketException
    111     {
    112         super(TFTPPacket.ACKNOWLEDGEMENT, datagram.getAddress(),
    113               datagram.getPort());
    114         byte[] data;
    115
    116         data = datagram.getData();
    117
    118         if (getType() != data[1])
    119             throw new TFTPPacketException("TFTP operator code does not match type.");
    120
    121         _blockNumber = (((data[2] & 0xff) << 8) | (data[3] & 0xff));
    122     }
    123
    124     /****
    125      * This is a method only available within the package for
    126      * implementing efficient datagram transport by elminating buffering.
    127      * It takes a datagram as an argument, and a byte buffer in which
    128      * to store the raw datagram data.  Inside the method, the data
    129      * is set as the datagram's data and the datagram returned.
    130      * <p>
    131      * @param datagram  The datagram to create.
    132      * @param data The buffer to store the packet and to use in the datagram.
    133      * @return The datagram argument.
    134      ***/
    135     DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
    136     {
    137         data[0] = 0;
    138         data[1] = (byte)_type;
    139         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
    140         data[3] = (byte)(_blockNumber & 0xff);
    141
    142         datagram.setAddress(_address);
    143         datagram.setPort(_port);
    144         datagram.setData(data);
    145         datagram.setLength(4);
    146
    147         return datagram;
    148     }
    149
    150
    151     /****
    152      * Creates a UDP datagram containing all the TFTP
    153      * acknowledgement packet data in the proper format.
    154      * This is a method exposed to the programmer in case he
    155      * wants to implement his own TFTP client instead of using
    156      * the <a href="org.apache.commons.net.tftp.TFTPClient.html#_top_">TFTPClient</a>
    157      * class.  Under normal circumstances, you should not have a need to call this
    158      * method.
    159      * <p>
    160      * @return A UDP datagram containing the TFTP acknowledgement packet.
    161      ***/
    162     public DatagramPacket newDatagram()
    163     {
    164         byte[] data;
    165
    166         data = new byte[4];
    167         data[0] = 0;
    168         data[1] = (byte)_type;
    169         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
    170         data[3] = (byte)(_blockNumber & 0xff);
    171
    172         return new DatagramPacket(data, data.length, _address, _port);
    173     }
    174
    175
    176     /****
    177      * Returns the block number of the acknowledgement.
    178      * <p>
    179      * @return The block number of the acknowledgement.
    180      ***/
    181     public int getBlockNumber()
    182     {
    183         return _blockNumber;
    184     }
    185
    186
    187     /**** Sets the block number of the acknowledgement.  ***/
    188     public void setBlockNumber(int blockNumber)
    189     {
    190         _blockNumber = blockNumber;
    191     }
    192 }
    193

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