TFTPDataPacket.java
/*
* 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 defining 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 eliminating 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;
}
}