    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 * <p>
    038 * <p>
    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     * <p>
    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     * <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
    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     * <p>
    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     * <p>
    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     * <p>
    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    public void setBlockNumber(int blockNumber)
    203    {
    204        _blockNumber = blockNumber;
    205    }
    206
    207    /***
    208     * Sets the data for the data packet.
    209     * <p>
    210     * @param data The byte array containing the data.
    211     * @param offset The offset into the array where the data starts.
    212     * @param length The length of the data.
    213     ***/
    214    public void setData(byte[] data, int offset, int length)
    215    {
    216        _data = data;
    217        _offset = offset;
    218        _length = length;
    219
    220        if (length > MAX_DATA_LENGTH) {
    221            _length = MAX_DATA_LENGTH;
    222        } else {
    223            _length = length;
    224        }
    225    }
    226
    227    /***
    228     * Returns the length of the data part of the data packet.
    229     * <p>
    230     * @return The length of the data part of the data packet.
    231     ***/
    232    public int getDataLength()
    233    {
    234        return _length;
    235    }
    236
    237    /***
    238     * Returns the offset into the byte array where the packet data actually
    239     * starts.
    240     * <p>
    241     * @return The offset into the byte array where the packet data actually
    242     *         starts.
    243     ***/
    244    public int getDataOffset()
    245    {
    246        return _offset;
    247    }
    248
    249    /***
    250     * Returns the byte array containing the packet data.
    251     * <p>
    252     * @return The byte array containing the packet data.
    253     ***/
    254    public byte[] getData()
    255    {
    256        return _data;
    257    }
    258}