    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    }