    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     * @see TFTPPacket
    040     * @see TFTPPacketException
    041     * @see TFTP
    042     ***/
    043
    044    public 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        public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
    095                              byte[] data)
    096        {
    097            this(destination, port, blockNumber, data, 0, data.length);
    098        }
    099
    100
    101        /***
    102         * Creates a data packet based from a received
    103         * datagram.  Assumes the datagram is at least length 4, else an
    104         * ArrayIndexOutOfBoundsException may be thrown.
    105         * <p>
    106         * @param datagram  The datagram containing the received data.
    107         * @throws TFTPPacketException  If the datagram isn't a valid TFTP
    108         *         data packet.
    109         ***/
    110        TFTPDataPacket(DatagramPacket datagram) throws TFTPPacketException
    111        {
    112            super(TFTPPacket.DATA, datagram.getAddress(), datagram.getPort());
    113
    114            _data = datagram.getData();
    115            _offset = 4;
    116
    117            if (getType() != _data[1])
    118                throw new TFTPPacketException("TFTP operator code does not match type.");
    119
    120            _blockNumber = (((_data[2] & 0xff) << 8) | (_data[3] & 0xff));
    121
    122            _length = datagram.getLength() - 4;
    123
    124            if (_length > MAX_DATA_LENGTH)
    125                _length = MAX_DATA_LENGTH;
    126        }
    127
    128        /***
    129         * This is a method only available within the package for
    130         * implementing efficient datagram transport by elminating buffering.
    131         * It takes a datagram as an argument, and a byte buffer in which
    132         * to store the raw datagram data.  Inside the method, the data
    133         * is set as the datagram's data and the datagram returned.
    134         * <p>
    135         * @param datagram  The datagram to create.
    136         * @param data The buffer to store the packet and to use in the datagram.
    137         * @return The datagram argument.
    138         ***/
    139        @Override
    140        DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
    141        {
    142            data[0] = 0;
    143            data[1] = (byte)_type;
    144            data[2] = (byte)((_blockNumber & 0xffff) >> 8);
    145            data[3] = (byte)(_blockNumber & 0xff);
    146
    147            // Doublecheck we're not the same
    148            if (data != _data)
    149                System.arraycopy(_data, _offset, data, 4, _length);
    150
    151            datagram.setAddress(_address);
    152            datagram.setPort(_port);
    153            datagram.setData(data);
    154            datagram.setLength(_length + 4);
    155
    156            return datagram;
    157        }
    158
    159        /***
    160         * Creates a UDP datagram containing all the TFTP
    161         * data packet data in the proper format.
    162         * This is a method exposed to the programmer in case he
    163         * wants to implement his own TFTP client instead of using
    164         * the {@link org.apache.commons.net.tftp.TFTPClient}
    165         * class.
    166         * Under normal circumstances, you should not have a need to call this
    167         * method.
    168         * <p>
    169         * @return A UDP datagram containing the TFTP data packet.
    170         ***/
    171        @Override
    172        public DatagramPacket newDatagram()
    173        {
    174            byte[] data;
    175
    176            data = new byte[_length + 4];
    177            data[0] = 0;
    178            data[1] = (byte)_type;
    179            data[2] = (byte)((_blockNumber & 0xffff) >> 8);
    180            data[3] = (byte)(_blockNumber & 0xff);
    181
    182            System.arraycopy(_data, _offset, data, 4, _length);
    183
    184            return new DatagramPacket(data, _length + 4, _address, _port);
    185        }
    186
    187        /***
    188         * Returns the block number of the data packet.
    189         * <p>
    190         * @return The block number of the data packet.
    191         ***/
    192        public int getBlockNumber()
    193        {
    194            return _blockNumber;
    195        }
    196
    197        /*** Sets the block number of the data packet.  ***/
    198        public void setBlockNumber(int blockNumber)
    199        {
    200            _blockNumber = blockNumber;
    201        }
    202
    203        /***
    204         * Sets the data for the data packet.
    205         * <p>
    206         * @param data The byte array containing the data.
    207         * @param offset The offset into the array where the data starts.
    208         * @param length The length of the data.
    209         ***/
    210        public void setData(byte[] data, int offset, int length)
    211        {
    212            _data = data;
    213            _offset = offset;
    214            _length = length;
    215
    216            if (length > MAX_DATA_LENGTH)
    217                _length = MAX_DATA_LENGTH;
    218            else
    219                _length = length;
    220        }
    221
    222        /***
    223         * Returns the length of the data part of the data packet.
    224         * <p>
    225         * @return The length of the data part of the data packet.
    226         ***/
    227        public int getDataLength()
    228        {
    229            return _length;
    230        }
    231
    232        /***
    233         * Returns the offset into the byte array where the packet data actually
    234         * starts.
    235         * <p>
    236         * @return The offset into the byte array where the packet data actually
    237         *         starts.
    238         ***/
    239        public int getDataOffset()
    240        {
    241            return _offset;
    242        }
    243
    244        /***
    245         * Returns the byte array containing the packet data.
    246         * <p>
    247         * @return The byte array containing the packet data.
    248         ***/
    249        public byte[] getData()
    250        {
    251            return _data;
    252        }
    253    }