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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   * @author Daniel F. Savarese
40   * @see TFTPPacket
41   * @see TFTPPacketException
42   * @see TFTP
43   ***/
44  
45  public final class TFTPDataPacket extends TFTPPacket
46  {
47      /*** The maximum number of bytes in a TFTP data packet (512) ***/
48      public static final int MAX_DATA_LENGTH = 512;
49  
50      /*** The minimum number of bytes in a TFTP data packet (0) ***/
51      public static final int MIN_DATA_LENGTH = 0;
52  
53      /*** The block number of the packet. ***/
54      int _blockNumber;
55  
56      /*** The length of the data. ***/
57      int _length;
58  
59      /*** The offset into the _data array at which the data begins. ***/
60      int _offset;
61  
62      /*** The data stored in the packet. ***/
63      byte[] _data;
64  
65      /***
66       * Creates a data packet to be sent to a host at a given port
67       * with a given block number.  The actual data to be sent is passed as
68       * an array, an offset, and a length.  The offset is the offset into
69       * the byte array where the data starts.  The length is the length of
70       * the data.  If the length is greater than MAX_DATA_LENGTH, it is
71       * truncated.
72       * <p>
73       * @param destination  The host to which the packet is going to be sent.
74       * @param port  The port to which the packet is going to be sent.
75       * @param blockNumber The block number of the data.
76       * @param data The byte array containing the data.
77       * @param offset The offset into the array where the data starts.
78       * @param length The length of the data.
79       ***/
80      public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
81                            byte[] data, int offset, int length)
82      {
83          super(TFTPPacket.DATA, destination, port);
84  
85          _blockNumber = blockNumber;
86          _data = data;
87          _offset = offset;
88  
89          if (length > MAX_DATA_LENGTH)
90              _length = MAX_DATA_LENGTH;
91          else
92              _length = length;
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         _blockNumber = (((_data[2] & 0xff) << 8) | (_data[3] & 0xff));
122 
123         _length = datagram.getLength() - 4;
124 
125         if (_length > MAX_DATA_LENGTH)
126             _length = MAX_DATA_LENGTH;
127     }
128 
129     /***
130      * This is a method only available within the package for
131      * implementing efficient datagram transport by elminating buffering.
132      * It takes a datagram as an argument, and a byte buffer in which
133      * to store the raw datagram data.  Inside the method, the data
134      * is set as the datagram's data and the datagram returned.
135      * <p>
136      * @param datagram  The datagram to create.
137      * @param data The buffer to store the packet and to use in the datagram.
138      * @return The datagram argument.
139      ***/
140     @Override
141     DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
142     {
143         data[0] = 0;
144         data[1] = (byte)_type;
145         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
146         data[3] = (byte)(_blockNumber & 0xff);
147 
148         // Doublecheck we're not the same
149         if (data != _data)
150             System.arraycopy(_data, _offset, data, 4, _length);
151 
152         datagram.setAddress(_address);
153         datagram.setPort(_port);
154         datagram.setData(data);
155         datagram.setLength(_length + 4);
156 
157         return datagram;
158     }
159 
160     /***
161      * Creates a UDP datagram containing all the TFTP
162      * data packet data in the proper format.
163      * This is a method exposed to the programmer in case he
164      * wants to implement his own TFTP client instead of using
165      * the {@link org.apache.commons.net.tftp.TFTPClient}
166      * class.
167      * Under normal circumstances, you should not have a need to call this
168      * method.
169      * <p>
170      * @return A UDP datagram containing the TFTP data packet.
171      ***/
172     @Override
173     public DatagramPacket newDatagram()
174     {
175         byte[] data;
176 
177         data = new byte[_length + 4];
178         data[0] = 0;
179         data[1] = (byte)_type;
180         data[2] = (byte)((_blockNumber & 0xffff) >> 8);
181         data[3] = (byte)(_blockNumber & 0xff);
182 
183         System.arraycopy(_data, _offset, data, 4, _length);
184 
185         return new DatagramPacket(data, _length + 4, _address, _port);
186     }
187 
188     /***
189      * Returns the block number of the data packet.
190      * <p>
191      * @return The block number of the data packet.
192      ***/
193     public int getBlockNumber()
194     {
195         return _blockNumber;
196     }
197 
198     /*** Sets the block number of the data packet.  ***/
199     public void setBlockNumber(int blockNumber)
200     {
201         _blockNumber = blockNumber;
202     }
203 
204     /***
205      * Sets the data for the data packet.
206      * <p>
207      * @param data The byte array containing the data.
208      * @param offset The offset into the array where the data starts.
209      * @param length The length of the data.
210      ***/
211     public void setData(byte[] data, int offset, int length)
212     {
213         _data = data;
214         _offset = offset;
215         _length = length;
216 
217         if (length > MAX_DATA_LENGTH)
218             _length = MAX_DATA_LENGTH;
219         else
220             _length = length;
221     }
222 
223     /***
224      * Returns the length of the data part of the data packet.
225      * <p>
226      * @return The length of the data part of the data packet.
227      ***/
228     public int getDataLength()
229     {
230         return _length;
231     }
232 
233     /***
234      * Returns the offset into the byte array where the packet data actually
235      * starts.
236      * <p>
237      * @return The offset into the byte array where the packet data actually
238      *         starts.
239      ***/
240     public int getDataOffset()
241     {
242         return _offset;
243     }
244 
245     /***
246      * Returns the byte array containing the packet data.
247      * <p>
248      * @return The byte array containing the packet data.
249      ***/
250     public byte[] getData()
251     {
252         return _data;
253     }
254 }