TFTPErrorPacket

/*
 * 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;
import java.nio.charset.Charset;

/**
 * A final class derived from TFTPPacket defining the TFTP Error 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 TFTPErrorPacket extends TFTPPacket {
    /** The undefined error code according to RFC 783, value 0. */
    public static final int UNDEFINED = 0;

    /** The file not found error code according to RFC 783, value 1. */
    public static final int FILE_NOT_FOUND = 1;

    /** The access violation error code according to RFC 783, value 2. */
    public static final int ACCESS_VIOLATION = 2;

    /** The disk full error code according to RFC 783, value 3. */
    public static final int OUT_OF_SPACE = 3;

    /**
     * The illegal TFTP operation error code according to RFC 783, value 4.
     */
    public static final int ILLEGAL_OPERATION = 4;

    /** The unknown transfer id error code according to RFC 783, value 5. */
    public static final int UNKNOWN_TID = 5;

    /** The file already exists error code according to RFC 783, value 6. */
    public static final int FILE_EXISTS = 6;

    /** The no such user error code according to RFC 783, value 7. */
    public static final int NO_SUCH_USER = 7;

    /** The error code of this packet. */
    private final int error;

    /** The error message of this packet. */
    private final String message;

    /**
     * Creates an error 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 error.
     * @throws TFTPPacketException If the datagram isn't a valid TFTP error packet.
     */
    TFTPErrorPacket(final DatagramPacket datagram) throws TFTPPacketException {
        super(TFTPPacket.ERROR, datagram.getAddress(), datagram.getPort());
        int index;
        final int length;
        final byte[] data;
        final StringBuilder buffer;

        data = datagram.getData();
        length = datagram.getLength();

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

        error = (data[2] & 0xff) << 8 | data[3] & 0xff;

        if (length < 5) {
            throw new TFTPPacketException("Bad error packet. No message.");
        }

        index = 4;
        buffer = new StringBuilder();

        while (index < length && data[index] != 0) {
            buffer.append((char) data[index]);
            ++index;
        }

        message = buffer.toString();
    }

    /**
     * Creates an error packet to be sent to a host at a given port with an error code and error message.
     *
     * @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 error       The error code of the packet.
     * @param message     The error message of the packet.
     */
    public TFTPErrorPacket(final InetAddress destination, final int port, final int error, final String message) {
        super(TFTPPacket.ERROR, destination, port);

        this.error = error;
        this.message = message;
    }

    /**
     * Returns the error code of the packet.
     *
     * @return The error code of the packet.
     */
    public int getError() {
        return error;
    }

    /**
     * Returns the error message of the packet.
     *
     * @return The error message of the packet.
     */
    public String getMessage() {
        return message;
    }

    /**
     * Creates a UDP datagram containing all the TFTP error 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 error packet.
     */
    @Override
    public DatagramPacket newDatagram() {
        final byte[] data;
        final int length;

        length = message.length();

        data = new byte[length + 5];
        data[0] = 0;
        data[1] = (byte) type;
        data[2] = (byte) ((error & 0xffff) >> 8);
        data[3] = (byte) (error & 0xff);

        System.arraycopy(message.getBytes(Charset.defaultCharset()), 0, data, 4, length);

        data[length + 4] = 0;

        return new DatagramPacket(data, data.length, 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) {
        final int length;

        length = message.length();

        data[0] = 0;
        data[1] = (byte) type;
        data[2] = (byte) ((error & 0xffff) >> 8);
        data[3] = (byte) (error & 0xff);

        System.arraycopy(message.getBytes(Charset.defaultCharset()), 0, data, 4, length);

        data[length + 4] = 0;

        datagram.setAddress(address);
        datagram.setPort(port);
        datagram.setData(data);
        datagram.setLength(length + 4);

        return datagram;
    }

    /**
     * For debugging
     *
     * @since 3.6
     */
    @Override
    public String toString() {
        return super.toString() + " ERR " + error + " " + message;
    }
}