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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.net.tftp;
19  
20  import java.net.DatagramPacket;
21  import java.net.InetAddress;
22  
23  /***
24   * A final class derived from TFTPPacket definiing the TFTP Data
25   * packet type.
26   * <p>
27   * Details regarding the TFTP protocol and the format of TFTP packets can
28   * be found in RFC 783.  But the point of these classes is to keep you
29   * from having to worry about the internals.  Additionally, only very
30   * few people should have to care about any of the TFTPPacket classes
31   * or derived classes.  Almost all users should only be concerned with the
32   * {@link org.apache.commons.net.tftp.TFTPClient} class
33   * {@link org.apache.commons.net.tftp.TFTPClient#receiveFile receiveFile()}
34   * and
35   * {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()}
36   * methods.
37   * <p>
38   * <p>
39   * @see TFTPPacket
40   * @see TFTPPacketException
41   * @see TFTP
42   ***/
43  
44  public final class TFTPDataPacket extends TFTPPacket
45  {
46      /*** The maximum number of bytes in a TFTP data packet (512) ***/
47      public static final int MAX_DATA_LENGTH = 512;
48  
49      /*** The minimum number of bytes in a TFTP data packet (0) ***/
50      public static final int MIN_DATA_LENGTH = 0;
51  
52      /*** The block number of the packet. ***/
53      int _blockNumber;
54  
55      /*** The length of the data. ***/
56      int _length;
57  
58      /*** The offset into the _data array at which the data begins. ***/
59      int _offset;
60  
61      /*** The data stored in the packet. ***/
62      byte[] _data;
63  
64      /***
65       * Creates a data packet to be sent to a host at a given port
66       * with a given block number.  The actual data to be sent is passed as
67       * an array, an offset, and a length.  The offset is the offset into
68       * the byte array where the data starts.  The length is the length of
69       * the data.  If the length is greater than MAX_DATA_LENGTH, it is
70       * truncated.
71       * <p>
72       * @param destination  The host to which the packet is going to be sent.
73       * @param port  The port to which the packet is going to be sent.
74       * @param blockNumber The block number of the data.
75       * @param data The byte array containing the data.
76       * @param offset The offset into the array where the data starts.
77       * @param length The length of the data.
78       ***/
79      public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
80                            byte[] data, int offset, int length)
81      {
82          super(TFTPPacket.DATA, destination, port);
83  
84          _blockNumber = blockNumber;
85          _data = data;
86          _offset = offset;
87  
88          if (length > MAX_DATA_LENGTH) {
89              _length = MAX_DATA_LENGTH;
90          } else {
91              _length = length;
92          }
93      }
94  
95      public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
96                            byte[] data)
97      {
98          this(destination, port, blockNumber, data, 0, data.length);
99      }
100 
101 
102     /***
103      * Creates a data packet based from a received
104      * datagram.  Assumes the datagram is at least length 4, else an
105      * ArrayIndexOutOfBoundsException may be thrown.
106      * <p>
107      * @param datagram  The datagram containing the received data.
108      * @throws TFTPPacketException  If the datagram isn't a valid TFTP
109      *         data packet.
110      ***/
111     TFTPDataPacket(DatagramPacket datagram) throws TFTPPacketException
112     {
113         super(TFTPPacket.DATA, datagram.getAddress(), datagram.getPort());
114 
115         _data = datagram.getData();
116         _offset = 4;
117 
118         if (getType() != _data[1]) {
119             throw new TFTPPacketException("TFTP operator code does not match type.");
120         }
121 
122         _blockNumber = (((_data[2] & 0xff) << 8) | (_data[3] & 0xff));
123 
124         _length = datagram.getLength() - 4;
125 
126         if (_length > MAX_DATA_LENGTH) {
127             _length = MAX_DATA_LENGTH;
128         }
129     }
130 
131     /***
132      * This is a method only available within the package for
133      * implementing efficient datagram transport by elminating buffering.
134      * It takes a datagram as an argument, and a byte buffer in which
135      * to store the raw datagram data.  Inside the method, the data
136      * is set as the datagram's data and the datagram returned.
137      * <p>
138      * @param datagram  The datagram to create.
139      * @param data The buffer to store the packet and to use in the datagram.
140      * @return The datagram argument.
141      ***/
142     @Override
143     DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
144     {
145         data[0] = 0;
146         data[1] = (byte)_type;
147         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
148         data[3] = (byte)(_blockNumber & 0xff);
149 
150         // Doublecheck we're not the same
151         if (data != _data) {
152             System.arraycopy(_data, _offset, data, 4, _length);
153         }
154 
155         datagram.setAddress(_address);
156         datagram.setPort(_port);
157         datagram.setData(data);
158         datagram.setLength(_length + 4);
159 
160         return datagram;
161     }
162 
163     /***
164      * Creates a UDP datagram containing all the TFTP
165      * data packet data in the proper format.
166      * This is a method exposed to the programmer in case he
167      * wants to implement his own TFTP client instead of using
168      * the {@link org.apache.commons.net.tftp.TFTPClient}
169      * class.
170      * Under normal circumstances, you should not have a need to call this
171      * method.
172      * <p>
173      * @return A UDP datagram containing the TFTP data packet.
174      ***/
175     @Override
176     public DatagramPacket newDatagram()
177     {
178         byte[] data;
179 
180         data = new byte[_length + 4];
181         data[0] = 0;
182         data[1] = (byte)_type;
183         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
184         data[3] = (byte)(_blockNumber & 0xff);
185 
186         System.arraycopy(_data, _offset, data, 4, _length);
187 
188         return new DatagramPacket(data, _length + 4, _address, _port);
189     }
190 
191     /***
192      * Returns the block number of the data packet.
193      * <p>
194      * @return The block number of the data packet.
195      ***/
196     public int getBlockNumber()
197     {
198         return _blockNumber;
199     }
200 
201     /*** Sets the block number of the data packet.  ***/
202     public void setBlockNumber(int blockNumber)
203     {
204         _blockNumber = blockNumber;
205     }
206 
207     /***
208      * Sets the data for the data packet.
209      * <p>
210      * @param data The byte array containing the data.
211      * @param offset The offset into the array where the data starts.
212      * @param length The length of the data.
213      ***/
214     public void setData(byte[] data, int offset, int length)
215     {
216         _data = data;
217         _offset = offset;
218         _length = length;
219 
220         if (length > MAX_DATA_LENGTH) {
221             _length = MAX_DATA_LENGTH;
222         } else {
223             _length = length;
224         }
225     }
226 
227     /***
228      * Returns the length of the data part of the data packet.
229      * <p>
230      * @return The length of the data part of the data packet.
231      ***/
232     public int getDataLength()
233     {
234         return _length;
235     }
236 
237     /***
238      * Returns the offset into the byte array where the packet data actually
239      * starts.
240      * <p>
241      * @return The offset into the byte array where the packet data actually
242      *         starts.
243      ***/
244     public int getDataOffset()
245     {
246         return _offset;
247     }
248 
249     /***
250      * Returns the byte array containing the packet data.
251      * <p>
252      * @return The byte array containing the packet data.
253      ***/
254     public byte[] getData()
255     {
256         return _data;
257     }
258 }