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    private int length;
057
058    /** The offset into the _data array at which the data begins. */
059    private int offset;
060
061    /** The data stored in the packet. */
062    private 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(final InetAddress destination, final int port, final int blockNumber,
080                          final byte[] data, final int offset, final int length)
081    {
082        super(TFTPPacket.DATA, destination, port);
083
084        this.blockNumber = blockNumber;
085        this.data = data;
086        this.offset = offset;
087
088        if (length > MAX_DATA_LENGTH) {
089            this.length = MAX_DATA_LENGTH;
090        } else {
091            this.length = length;
092        }
093    }
094
095    public TFTPDataPacket(final InetAddress destination, final int port, final int blockNumber,
096                          final 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(final DatagramPacket datagram) throws TFTPPacketException
112    {
113        super(TFTPPacket.DATA, datagram.getAddress(), datagram.getPort());
114
115        this.data = datagram.getData();
116        this.offset = 4;
117
118        if (getType() != this.data[1]) {
119            throw new TFTPPacketException("TFTP operator code does not match type.");
120        }
121
122        this.blockNumber = (((this.data[2] & 0xff) << 8) | (this.data[3] & 0xff));
123
124        this.length = datagram.getLength() - 4;
125
126        if (this.length > MAX_DATA_LENGTH) {
127            this.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(final DatagramPacket datagram, final 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 != this.data) {
152            System.arraycopy(this.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        final 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(this.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(final int blockNumber)
205    {
206        this.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(final byte[] data, final int offset, final int length)
217    {
218        this.data = data;
219        this.offset = offset;
220        this.length = length;
221
222        if (length > MAX_DATA_LENGTH) {
223            this.length = MAX_DATA_LENGTH;
224        } else {
225            this.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
261    /**
262     * For debugging
263     * @since 3.6
264     */
265    @Override
266    public String toString() {
267        return super.toString() + " DATA " + blockNumber + " " + length;
268    }
269}