    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.telnet;
    019
    020/***
    021 * Implements the telnet window size option RFC 1073.
    022 * @since 2.0
    023 ***/
    024public class WindowSizeOptionHandler extends TelnetOptionHandler
    025{
    026    /***
    027     * Horizontal Size
    028     ***/
    029    private int width = 80;
    030
    031    /***
    032     * Vertical Size
    033     ***/
    034    private int height = 24;
    035
    036    /***
    037     * Window size option
    038     ***/
    039    protected static final int WINDOW_SIZE = 31;
    040
    041    /***
    042     * Constructor for the WindowSizeOptionHandler. Allows defining desired
    043     * initial setting for local/remote activation of this option and
    044     * behavior in case a local/remote activation request for this
    045     * option is received.
    046     * <p>
    047     * @param nWidth - Window width.
    048     * @param nHeight - Window Height
    049     * @param initlocal - if set to true, a WILL is sent upon connection.
    050     * @param initremote - if set to true, a DO is sent upon connection.
    051     * @param acceptlocal - if set to true, any DO request is accepted.
    052     * @param acceptremote - if set to true, any WILL request is accepted.
    053     ***/
    054    public WindowSizeOptionHandler(
    055        final int nWidth,
    056        final int nHeight,
    057        final boolean initlocal,
    058        final boolean initremote,
    059        final boolean acceptlocal,
    060        final boolean acceptremote
    061    ) {
    062        super (
    063            TelnetOption.WINDOW_SIZE,
    064            initlocal,
    065            initremote,
    066            acceptlocal,
    067            acceptremote
    068        );
    069
    070        width = nWidth;
    071        height = nHeight;
    072    }
    073
    074    /***
    075     * Constructor for the WindowSizeOptionHandler. Initial and accept
    076     * behavior flags are set to false
    077     * <p>
    078     * @param nWidth - Window width.
    079     * @param nHeight - Window Height
    080     ***/
    081    public WindowSizeOptionHandler(
    082        final int nWidth,
    083        final int nHeight
    084    ) {
    085        super (
    086            TelnetOption.WINDOW_SIZE,
    087            false,
    088            false,
    089            false,
    090            false
    091        );
    092
    093        width = nWidth;
    094        height = nHeight;
    095    }
    096
    097    /***
    098     * Implements the abstract method of TelnetOptionHandler.
    099     * This will send the client Height and Width to the server.
    100     * <p>
    101     * @return array to send to remote system
    102     ***/
    103    @Override
    104    public int[] startSubnegotiationLocal()
    105    {
    106        final int nCompoundWindowSize = width * 0x10000 + height;
    107        int nResponseSize = 5;
    108        int nIndex;
    109        int nShift;
    110        int nTurnedOnBits;
    111
    112        if (width % 0x100 == 0xFF) {
    113            nResponseSize += 1;
    114        }
    115
    116        if (width / 0x100 == 0xFF) {
    117            nResponseSize += 1;
    118        }
    119
    120        if (height % 0x100 == 0xFF) {
    121            nResponseSize += 1;
    122        }
    123
    124        if (height / 0x100 == 0xFF) {
    125            nResponseSize += 1;
    126        }
    127
    128        //
    129        // allocate response array
    130        //
    131        final int response[] = new int[nResponseSize];
    132
    133        //
    134        // Build response array.
    135        // ---------------------
    136        // 1. put option name.
    137        // 2. loop through Window size and fill the values,
    138        // 3.    duplicate 'ff' if needed.
    139        //
    140
    141        response[0] = WINDOW_SIZE;                          // 1 //
    142
    143        for (                                               // 2 //
    144            nIndex=1, nShift = 24;
    145            nIndex < nResponseSize;
    146            nIndex++, nShift -=8
    147        ) {
    148            nTurnedOnBits = 0xFF;
    149            nTurnedOnBits <<= nShift;
    150            response[nIndex] = (nCompoundWindowSize & nTurnedOnBits) >>> nShift;
    151
    152            if (response[nIndex] == 0xff) {                 // 3 //
    153                nIndex++;
    154                response[nIndex] = 0xff;
    155            }
    156        }
    157
    158        return response;
    159    }
    160
    161}