001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.net.tftp;
019
020import java.net.DatagramPacket;
021import java.net.InetAddress;
022
023/***
024 * A final class derived from TFTPPacket definiing the TFTP Data
025 * packet type.
026 * <p>
027 * Details regarding the TFTP protocol and the format of TFTP packets can
028 * be found in RFC 783.  But the point of these classes is to keep you
029 * from having to worry about the internals.  Additionally, only very
030 * few people should have to care about any of the TFTPPacket classes
031 * or derived classes.  Almost all users should only be concerned with the
032 * {@link org.apache.commons.net.tftp.TFTPClient} class
033 * {@link org.apache.commons.net.tftp.TFTPClient#receiveFile receiveFile()}
034 * and
035 * {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()}
036 * methods.
037 *
038 *
039 * @see TFTPPacket
040 * @see TFTPPacketException
041 * @see TFTP
042 ***/
043
044public final class TFTPDataPacket extends TFTPPacket
045{
046    /*** The maximum number of bytes in a TFTP data packet (512) ***/
047    public static final int MAX_DATA_LENGTH = 512;
048
049    /*** The minimum number of bytes in a TFTP data packet (0) ***/
050    public static final int MIN_DATA_LENGTH = 0;
051
052    /*** The block number of the packet. ***/
053    int _blockNumber;
054
055    /*** The length of the data. ***/
056    int _length;
057
058    /*** The offset into the _data array at which the data begins. ***/
059    int _offset;
060
061    /*** The data stored in the packet. ***/
062    byte[] _data;
063
064    /***
065     * Creates a data packet to be sent to a host at a given port
066     * with a given block number.  The actual data to be sent is passed as
067     * an array, an offset, and a length.  The offset is the offset into
068     * the byte array where the data starts.  The length is the length of
069     * the data.  If the length is greater than MAX_DATA_LENGTH, it is
070     * truncated.
071     *
072     * @param destination  The host to which the packet is going to be sent.
073     * @param port  The port to which the packet is going to be sent.
074     * @param blockNumber The block number of the data.
075     * @param data The byte array containing the data.
076     * @param offset The offset into the array where the data starts.
077     * @param length The length of the data.
078     ***/
079    public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
080                          byte[] data, int offset, int length)
081    {
082        super(TFTPPacket.DATA, destination, port);
083
084        _blockNumber = blockNumber;
085        _data = data;
086        _offset = offset;
087
088        if (length > MAX_DATA_LENGTH) {
089            _length = MAX_DATA_LENGTH;
090        } else {
091            _length = length;
092        }
093    }
094
095    public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
096                          byte[] data)
097    {
098        this(destination, port, blockNumber, data, 0, data.length);
099    }
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     *
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     *
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     *
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     *
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     * @param blockNumber the number to set
203     ***/
204    public void setBlockNumber(int blockNumber)
205    {
206        _blockNumber = blockNumber;
207    }
208
209    /***
210     * Sets the data for the data packet.
211     *
212     * @param data The byte array containing the data.
213     * @param offset The offset into the array where the data starts.
214     * @param length The length of the data.
215     ***/
216    public void setData(byte[] data, int offset, int length)
217    {
218        _data = data;
219        _offset = offset;
220        _length = length;
221
222        if (length > MAX_DATA_LENGTH) {
223            _length = MAX_DATA_LENGTH;
224        } else {
225            _length = length;
226        }
227    }
228
229    /***
230     * Returns the length of the data part of the data packet.
231     *
232     * @return The length of the data part of the data packet.
233     ***/
234    public int getDataLength()
235    {
236        return _length;
237    }
238
239    /***
240     * Returns the offset into the byte array where the packet data actually
241     * starts.
242     *
243     * @return The offset into the byte array where the packet data actually
244     *         starts.
245     ***/
246    public int getDataOffset()
247    {
248        return _offset;
249    }
250
251    /***
252     * Returns the byte array containing the packet data.
253     *
254     * @return The byte array containing the packet data.
255     ***/
256    public byte[] getData()
257    {
258        return _data;
259    }
260}