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TFTPDataPacket.java
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TFTPDataPacket.java
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/*
* 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.
* <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) */
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. */
private int length;
/** The offset into the _data array at which the data begins. */
private int offset;
/** The data stored in the packet. */
private byte[] data;
/**
* 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(final DatagramPacket datagram) throws TFTPPacketException
{
super(TFTPPacket.DATA, datagram.getAddress(), datagram.getPort());
this.data = datagram.getData();
this.offset = 4;
if (getType() != this.data[1]) {
throw new TFTPPacketException("TFTP operator code does not match type.");
}
this.blockNumber = (((this.data[2] & 0xff) << 8) | (this.data[3] & 0xff));
this.length = datagram.getLength() - 4;
if (this.length > MAX_DATA_LENGTH) {
this.length = MAX_DATA_LENGTH;
}
}
public TFTPDataPacket(final InetAddress destination, final int port, final int blockNumber,
final byte[] data)
{
this(destination, port, blockNumber, data, 0, data.length);
}
/**
* 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(final InetAddress destination, final int port, final int blockNumber,
final byte[] data, final int offset, final int length)
{
super(TFTPPacket.DATA, destination, port);
this.blockNumber = blockNumber;
this.data = data;
this.offset = offset;
this.length = Math.min(length, MAX_DATA_LENGTH);
}
/**
* Returns the block number of the data packet.
*
* @return The block number of the data packet.
*/
public int getBlockNumber()
{
return blockNumber;
}
/**
* Returns the byte array containing the packet data.
*
* @return The byte array containing the packet data.
*/
public byte[] getData()
{
return data;
}
/**
* 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;
}
/**
* 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()
{
final 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(this.data, offset, data, 4, length);
return new DatagramPacket(data, length + 4, address, port);
}
/**
* 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(final DatagramPacket datagram, final 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 != this.data) {
System.arraycopy(this.data, offset, data, 4, length);
}
datagram.setAddress(address);
datagram.setPort(port);
datagram.setData(data);
datagram.setLength(length + 4);
return datagram;
}
/** Sets the block number of the data packet.
* @param blockNumber the number to set
*/
public void setBlockNumber(final int blockNumber)
{
this.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(final byte[] data, final int offset, final int length)
{
this.data = data;
this.offset = offset;
this.length = length;
this.length = Math.min(length, MAX_DATA_LENGTH);
}
/**
* For debugging
* @since 3.6
*/
@Override
public String toString() {
return super.toString() + " DATA " + blockNumber + " " + length;
}
}