    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
    018package org.apache.commons.net.tftp;
    019
    020import java.net.DatagramPacket;
    021import java.net.InetAddress;
    022
    023/**
    024 * A final class derived from TFTPPacket definiing the TFTP Acknowledgement packet type.
    025 * <p>
    026 * 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
    027 * 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
    028 * should only be concerned with the {@link org.apache.commons.net.tftp.TFTPClient} class {@link org.apache.commons.net.tftp.TFTPClient#receiveFile
    029 * receiveFile()} and {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()} methods.
    030 *
    031 *
    032 * @see TFTPPacket
    033 * @see TFTPPacketException
    034 * @see TFTP
    035 */
    036
    037public final class TFTPAckPacket extends TFTPPacket {
    038    /** The block number being acknowledged by the packet. */
    039    int blockNumber;
    040
    041    /**
    042     * Creates an acknowledgement packet based from a received datagram. Assumes the datagram is at least length 4, else an ArrayIndexOutOfBoundsException may
    043     * be thrown.
    044     *
    045     * @param datagram The datagram containing the received acknowledgement.
    046     * @throws TFTPPacketException If the datagram isn't a valid TFTP acknowledgement packet.
    047     */
    048    TFTPAckPacket(final DatagramPacket datagram) throws TFTPPacketException {
    049        super(TFTPPacket.ACKNOWLEDGEMENT, datagram.getAddress(), datagram.getPort());
    050        final byte[] data;
    051
    052        data = datagram.getData();
    053
    054        if (getType() != data[1]) {
    055            throw new TFTPPacketException("TFTP operator code does not match type.");
    056        }
    057
    058        this.blockNumber = (((data[2] & 0xff) << 8) | (data[3] & 0xff));
    059    }
    060
    061    /**
    062     * Creates an acknowledgment packet to be sent to a host at a given port acknowledging receipt of a block.
    063     *
    064     * @param destination The host to which the packet is going to be sent.
    065     * @param port        The port to which the packet is going to be sent.
    066     * @param blockNumber The block number being acknowledged.
    067     */
    068    public TFTPAckPacket(final InetAddress destination, final int port, final int blockNumber) {
    069        super(TFTPPacket.ACKNOWLEDGEMENT, destination, port);
    070        this.blockNumber = blockNumber;
    071    }
    072
    073    /**
    074     * Returns the block number of the acknowledgement.
    075     *
    076     * @return The block number of the acknowledgement.
    077     */
    078    public int getBlockNumber() {
    079        return blockNumber;
    080    }
    081
    082    /**
    083     * Creates a UDP datagram containing all the TFTP acknowledgement packet data in the proper format. This is a method exposed to the programmer in case he
    084     * wants to implement his own TFTP client instead of using the {@link org.apache.commons.net.tftp.TFTPClient} class. Under normal circumstances, you should
    085     * not have a need to call this method.
    086     *
    087     * @return A UDP datagram containing the TFTP acknowledgement packet.
    088     */
    089    @Override
    090    public DatagramPacket newDatagram() {
    091        final byte[] data;
    092
    093        data = new byte[4];
    094        data[0] = 0;
    095        data[1] = (byte) type;
    096        data[2] = (byte) ((blockNumber & 0xffff) >> 8);
    097        data[3] = (byte) (blockNumber & 0xff);
    098
    099        return new DatagramPacket(data, data.length, address, port);
    100    }
    101
    102    /**
    103     * This is a method only available within the package for implementing efficient datagram transport by elminating buffering. It takes a datagram as an
    104     * 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.
    105     *
    106     * @param datagram The datagram to create.
    107     * @param data     The buffer to store the packet and to use in the datagram.
    108     * @return The datagram argument.
    109     */
    110    @Override
    111    DatagramPacket newDatagram(final DatagramPacket datagram, final byte[] data) {
    112        data[0] = 0;
    113        data[1] = (byte) type;
    114        data[2] = (byte) ((blockNumber & 0xffff) >> 8);
    115        data[3] = (byte) (blockNumber & 0xff);
    116
    117        datagram.setAddress(address);
    118        datagram.setPort(port);
    119        datagram.setData(data);
    120        datagram.setLength(4);
    121
    122        return datagram;
    123    }
    124
    125    /**
    126     * Sets the block number of the acknowledgement.
    127     *
    128     * @param blockNumber the number to set
    129     */
    130    public void setBlockNumber(final int blockNumber) {
    131        this.blockNumber = blockNumber;
    132    }
    133
    134    /**
    135     * For debugging
    136     *
    137     * @since 3.6
    138     */
    139    @Override
    140    public String toString() {
    141        return super.toString() + " ACK " + blockNumber;
    142    }
    143}