    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
    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    }