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Java > Open Source Codes > org > apache > commons > net > tftp > TFTPDataPacket


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 JavaDoc;
19 import java.net.InetAddress JavaDoc;
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 JavaDoc 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 JavaDoc 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 JavaDoc 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 JavaDoc _newDatagram(DatagramPacket JavaDoc 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 JavaDoc 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 JavaDoc(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 }
251
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