/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.tftp;

import java.net.DatagramPacket;
import java.net.InetAddress;

A final class derived from TFTPPacket definiing the TFTP Data
packet type.
 Details regarding the TFTP protocol and the format of TFTP packets can be found in RFC 783. But the point of these classes is to keep you from having to worry about the internals. Additionally, only very few people should have to care about any of the TFTPPacket classes or derived classes. Almost all users should only be concerned with the TFTPClient class receiveFile() and sendFile() methods. 
See Also:
TFTPPacket
TFTPPacketException
TFTP/***
 * A final class derived from TFTPPacket definiing the TFTP Data
 * packet type.
 * <p>
 * Details regarding the TFTP protocol and the format of TFTP packets can
 * be found in RFC 783.  But the point of these classes is to keep you
 * from having to worry about the internals.  Additionally, only very
 * few people should have to care about any of the TFTPPacket classes
 * or derived classes.  Almost all users should only be concerned with the
 * {@link org.apache.commons.net.tftp.TFTPClient} class
 * {@link org.apache.commons.net.tftp.TFTPClient#receiveFile receiveFile()}
 * and
 * {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()}
 * methods.
 *
 *
 * @see TFTPPacket
 * @see TFTPPacketException
 * @see TFTP
 ***/

public final class TFTPDataPacket extends TFTPPacket
{
    
The maximum number of bytes in a TFTP data packet (512) /*** The maximum number of bytes in a TFTP data packet (512) ***/
    public static final int MAX_DATA_LENGTH = 512;

    
The minimum number of bytes in a TFTP data packet (0) /*** The minimum number of bytes in a TFTP data packet (0) ***/
    public static final int MIN_DATA_LENGTH = 0;

    
The block number of the packet. /*** The block number of the packet. ***/
    int _blockNumber;

    
The length of the data. /*** The length of the data. ***/
    int _length;

    
The offset into the _data array at which the data begins. /*** The offset into the _data array at which the data begins. ***/
    int _offset;

    
The data stored in the packet. /*** The data stored in the packet. ***/
    byte[] _data;

    
Creates a data packet to be sent to a host at a given port
with a given block number.  The actual data to be sent is passed as
an array, an offset, and a length.  The offset is the offset into
the byte array where the data starts.  The length is the length of
the data.  If the length is greater than MAX_DATA_LENGTH, it is
truncated.
Params:
destination –  The host to which the packet is going to be sent.
port –  The port to which the packet is going to be sent.
blockNumber – The block number of the data.
data – The byte array containing the data.
offset – The offset into the array where the data starts.
length – The length of the data./***
     * Creates a data packet to be sent to a host at a given port
     * with a given block number.  The actual data to be sent is passed as
     * an array, an offset, and a length.  The offset is the offset into
     * the byte array where the data starts.  The length is the length of
     * the data.  If the length is greater than MAX_DATA_LENGTH, it is
     * truncated.
     *
     * @param destination  The host to which the packet is going to be sent.
     * @param port  The port to which the packet is going to be sent.
     * @param blockNumber The block number of the data.
     * @param data The byte array containing the data.
     * @param offset The offset into the array where the data starts.
     * @param length The length of the data.
     ***/
    public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
                          byte[] data, int offset, int length)
    {
        super(TFTPPacket.DATA, destination, port);

        _blockNumber = blockNumber;
        _data = data;
        _offset = offset;

        if (length > MAX_DATA_LENGTH) {
            _length = MAX_DATA_LENGTH;
        } else {
            _length = length;
        }
    }

    public TFTPDataPacket(InetAddress destination, int port, int blockNumber,
                          byte[] data)
    {
        this(destination, port, blockNumber, data, 0, data.length);
    }


    
Creates a data packet based from a received
datagram.  Assumes the datagram is at least length 4, else an
ArrayIndexOutOfBoundsException may be thrown.
Params:
datagram –  The datagram containing the received data.
Throws:
TFTPPacketException –  If the datagram isn't a valid TFTP
        data packet./***
     * Creates a data packet based from a received
     * datagram.  Assumes the datagram is at least length 4, else an
     * ArrayIndexOutOfBoundsException may be thrown.
     *
     * @param datagram  The datagram containing the received data.
     * @throws TFTPPacketException  If the datagram isn't a valid TFTP
     *         data packet.
     ***/
    TFTPDataPacket(DatagramPacket datagram) throws TFTPPacketException
    {
        super(TFTPPacket.DATA, datagram.getAddress(), datagram.getPort());

        _data = datagram.getData();
        _offset = 4;

        if (getType() != _data[1]) {
            throw new TFTPPacketException("TFTP operator code does not match type.");
        }

        _blockNumber = (((_data[2] & 0xff) << 8) | (_data[3] & 0xff));

        _length = datagram.getLength() - 4;

        if (_length > MAX_DATA_LENGTH) {
            _length = MAX_DATA_LENGTH;
        }
    }

    
This is a method only available within the package for
implementing efficient datagram transport by elminating buffering.
It takes a datagram as an argument, and a byte buffer in which
to store the raw datagram data.  Inside the method, the data
is set as the datagram's data and the datagram returned.
Params:
datagram –  The datagram to create.
data – The buffer to store the packet and to use in the datagram.
Returns:
The datagram argument./***
     * This is a method only available within the package for
     * implementing efficient datagram transport by elminating buffering.
     * It takes a datagram as an argument, and a byte buffer in which
     * to store the raw datagram data.  Inside the method, the data
     * is set as the datagram's data and the datagram returned.
     *
     * @param datagram  The datagram to create.
     * @param data The buffer to store the packet and to use in the datagram.
     * @return The datagram argument.
     ***/
    @Override
    DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
    {
        data[0] = 0;
        data[1] = (byte)_type;
        data[2] = (byte)((_blockNumber & 0xffff) >> 8);
        data[3] = (byte)(_blockNumber & 0xff);

        // Doublecheck we're not the same
        if (data != _data) {
            System.arraycopy(_data, _offset, data, 4, _length);
        }

        datagram.setAddress(_address);
        datagram.setPort(_port);
        datagram.setData(data);
        datagram.setLength(_length + 4);

        return datagram;
    }

    
Creates a UDP datagram containing all the TFTP data packet data in the proper format. This is a method exposed to the programmer in case he wants to implement his own TFTP client instead of using the TFTPClient class. Under normal circumstances, you should not have a need to call this method. 
Returns:
A UDP datagram containing the TFTP data packet./***
     * Creates a UDP datagram containing all the TFTP
     * data packet data in the proper format.
     * This is a method exposed to the programmer in case he
     * wants to implement his own TFTP client instead of using
     * the {@link org.apache.commons.net.tftp.TFTPClient}
     * class.
     * Under normal circumstances, you should not have a need to call this
     * method.
     *
     * @return A UDP datagram containing the TFTP data packet.
     ***/
    @Override
    public DatagramPacket newDatagram()
    {
        byte[] data;

        data = new byte[_length + 4];
        data[0] = 0;
        data[1] = (byte)_type;
        data[2] = (byte)((_blockNumber & 0xffff) >> 8);
        data[3] = (byte)(_blockNumber & 0xff);

        System.arraycopy(_data, _offset, data, 4, _length);

        return new DatagramPacket(data, _length + 4, _address, _port);
    }

    
Returns the block number of the data packet.
Returns:
The block number of the data packet./***
     * Returns the block number of the data packet.
     *
     * @return The block number of the data packet.
     ***/
    public int getBlockNumber()
    {
        return _blockNumber;
    }

    
Sets the block number of the data packet.
Params:
blockNumber – the number to set/*** Sets the block number of the data packet.
     * @param blockNumber the number to set
     ***/
    public void setBlockNumber(int blockNumber)
    {
        _blockNumber = blockNumber;
    }

    
Sets the data for the data packet.
Params:
data – The byte array containing the data.
offset – The offset into the array where the data starts.
length – The length of the data./***
     * Sets the data for the data packet.
     *
     * @param data The byte array containing the data.
     * @param offset The offset into the array where the data starts.
     * @param length The length of the data.
     ***/
    public void setData(byte[] data, int offset, int length)
    {
        _data = data;
        _offset = offset;
        _length = length;

        if (length > MAX_DATA_LENGTH) {
            _length = MAX_DATA_LENGTH;
        } else {
            _length = length;
        }
    }

    
Returns the length of the data part of the data packet.
Returns:
The length of the data part of the data packet./***
     * Returns the length of the data part of the data packet.
     *
     * @return The length of the data part of the data packet.
     ***/
    public int getDataLength()
    {
        return _length;
    }

    
Returns the offset into the byte array where the packet data actually
starts.
Returns:
The offset into the byte array where the packet data actually
        starts./***
     * Returns the offset into the byte array where the packet data actually
     * starts.
     *
     * @return The offset into the byte array where the packet data actually
     *         starts.
     ***/
    public int getDataOffset()
    {
        return _offset;
    }

    
Returns the byte array containing the packet data.
Returns:
The byte array containing the packet data./***
     * Returns the byte array containing the packet data.
     *
     * @return The byte array containing the packet data.
     ***/
    public byte[] getData()
    {
        return _data;
    }

    
For debugging
Since:
3.6/**
     * For debugging
     * @since 3.6
     */
    @Override
    public String toString() {
        return super.toString() + " DATA " + _blockNumber + " " + _length;
    }
}