panda.net.tftp.TFTPDataPacket Maven / Gradle / Ivy
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package panda.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 {@link panda.net.tftp.TFTPClient} class
* {@link panda.net.tftp.TFTPClient#receiveFile receiveFile()} and
* {@link panda.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) ***/
public static final int MAX_DATA_LENGTH = 512;
/*** 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. ***/
int _blockNumber;
/*** The length of the data. ***/
int _length;
/*** The offset into the _data array at which the data begins. ***/
int _offset;
/*** 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.
*
* @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.
*
* @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.
*
* @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 {@link panda.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.
*
* @return The block number of the data packet.
***/
public int getBlockNumber() {
return _blockNumber;
}
/***
* 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.
*
* @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.
*
* @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.
*
* @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.
*
* @return The byte array containing the packet data.
***/
public byte[] getData() {
return _data;
}
}