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    
018    package org.apache.commons.net.tftp;
019    
020    import java.net.DatagramPacket;
021    import 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     * <p>
038     * <p>
039     * @author Daniel F. Savarese
040     * @see TFTPPacket
041     * @see TFTPPacketException
042     * @see TFTP
043     ***/
044    
045    public final class TFTPDataPacket extends TFTPPacket
046    {
047        /*** The maximum number of bytes in a TFTP data packet (512) ***/
048        public static final int MAX_DATA_LENGTH = 512;
049    
050        /*** The minimum number of bytes in a TFTP data packet (0) ***/
051        public static final int MIN_DATA_LENGTH = 0;
052    
053        /*** The block number of the packet. ***/
054        int _blockNumber;
055    
056        /*** The length of the data. ***/
057        int _length;
058    
059        /*** The offset into the _data array at which the data begins. ***/
060        int _offset;
061    
062        /*** The data stored in the packet. ***/
063        byte[] _data;
064    
065        /***
066         * Creates a data packet to be sent to a host at a given port
067         * with a given block number.  The actual data to be sent is passed as
068         * an array, an offset, and a length.  The offset is the offset into
069         * the byte array where the data starts.  The length is the length of
070         * the data.  If the length is greater than MAX_DATA_LENGTH, it is
071         * truncated.
072         * <p>
073         * @param destination  The host to which the packet is going to be sent.
074         * @param port  The port to which the packet is going to be sent.
075         * @param blockNumber The block number of the data.
076         * @param data The byte array containing the data.
077         * @param offset The offset into the array where the data starts.
078         * @param length The length of the data.
079         ***/
080        public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
081                              byte[] data, int offset, int length)
082        {
083            super(TFTPPacket.DATA, destination, port);
084    
085            _blockNumber = blockNumber;
086            _data = data;
087            _offset = offset;
088    
089            if (length > MAX_DATA_LENGTH)
090                _length = MAX_DATA_LENGTH;
091            else
092                _length = length;
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         * <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    }