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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 }