WindowSizeOptionHandler.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.telnet;

/**
 * Implements the telnet window size option RFC 1073.
 *
 * @since 2.0
 */
public class WindowSizeOptionHandler extends TelnetOptionHandler {
    /**
     * Window size option
     */
    protected static final int WINDOW_SIZE = 31;

    /**
     * Horizontal Size
     */
    private int width = 80;

    /**
     * Vertical Size
     */
    private int height = 24;

    /**
     * Constructor for the WindowSizeOptionHandler. Initial and accept behavior flags are set to false
     *
     * @param nWidth  - Window width.
     * @param nHeight - Window Height
     */
    public WindowSizeOptionHandler(final int nWidth, final int nHeight) {
        super(TelnetOption.WINDOW_SIZE, false, false, false, false);

        width = nWidth;
        height = nHeight;
    }

    /**
     * Constructor for the WindowSizeOptionHandler. Allows defining desired initial setting for local/remote activation of this option and behavior in case a
     * local/remote activation request for this option is received.
     *
     * @param nWidth       - Window width.
     * @param nHeight      - Window Height
     * @param initlocal    - if set to true, a {@code WILL} is sent upon connection.
     * @param initremote   - if set to true, a {@code DO} is sent upon connection.
     * @param acceptlocal  - if set to true, any {@code DO} request is accepted.
     * @param acceptremote - if set to true, any {@code WILL} request is accepted.
     */
    public WindowSizeOptionHandler(final int nWidth, final int nHeight, final boolean initlocal, final boolean initremote, final boolean acceptlocal,
            final boolean acceptremote) {
        super(TelnetOption.WINDOW_SIZE, initlocal, initremote, acceptlocal, acceptremote);

        width = nWidth;
        height = nHeight;
    }

    /**
     * Implements the abstract method of TelnetOptionHandler. This will send the client Height and Width to the server.
     *
     * @return array to send to remote system
     */
    @Override
    public int[] startSubnegotiationLocal() {
        final int nCompoundWindowSize = width * 0x10000 + height;
        int nResponseSize = 5;
        int nIndex;
        int nShift;
        int nTurnedOnBits;

        if (width % 0x100 == 0xFF) {
            nResponseSize += 1;
        }

        if (width / 0x100 == 0xFF) {
            nResponseSize += 1;
        }

        if (height % 0x100 == 0xFF) {
            nResponseSize += 1;
        }

        if (height / 0x100 == 0xFF) {
            nResponseSize += 1;
        }

        //
        // allocate response array
        //
        final int[] response = new int[nResponseSize];

        //
        // Build response array.
        // ---------------------
        // 1. put option name.
        // 2. loop through Window size and fill the values,
        // 3. duplicate 'ff' if needed.
        //

        response[0] = WINDOW_SIZE; // 1 //

        for ( // 2 //
                nIndex = 1, nShift = 24; nIndex < nResponseSize; nIndex++, nShift -= 8) {
            nTurnedOnBits = 0xFF;
            nTurnedOnBits <<= nShift;
            response[nIndex] = (nCompoundWindowSize & nTurnedOnBits) >>> nShift;

            if (response[nIndex] == 0xff) { // 3 //
                nIndex++;
                response[nIndex] = 0xff;
            }
        }

        return response;
    }

}