Scala example source code file (UnixTerminal.java)

This example Scala source code file (UnixTerminal.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

arrow_start, arrow_up, del_third, end_code, exception, map, o_prefix, override, terminallinesettings, unixkey

The UnixTerminal.java Scala example source code

/*
 * Copyright (c) 2002-2007, Marc Prud'hommeaux. All rights reserved.
 *
 * This software is distributable under the BSD license. See the terms of the
 * BSD license in the documentation provided with this software.
 */

package scala.tools.jline;

import scala.tools.jline.console.Key;
import scala.tools.jline.internal.Configuration;
import scala.tools.jline.internal.Log;
import scala.tools.jline.internal.ReplayPrefixOneCharInputStream;
import scala.tools.jline.internal.TerminalLineSettings;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

import static scala.tools.jline.UnixTerminal.UnixKey.*;
import static scala.tools.jline.console.Key.*;

/**
 * Terminal that is used for unix platforms. Terminal initialization
 * is handled by issuing the <em>stty</em> command against the
 * <em>/dev/tty</em> file to disable character echoing and enable
 * character input. All known unix systems (including
 * Linux and Macintosh OS X) support the <em>stty</em>), so this
 * implementation should work for an reasonable POSIX system.
 *
 * @author <a href="mailto:mwp1@cornell.edu">Marc Prud'hommeaux</a>
 * @author <a href="mailto:dwkemp@gmail.com">Dale Kemp</a>
 * @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
 * @author <a href="mailto:jbonofre@apache.org">Jean-Baptiste Onofré</a>
 * @since 2.0
 */
public class UnixTerminal
    extends TerminalSupport
{
    private final TerminalLineSettings settings = new TerminalLineSettings();

    private final ReplayPrefixOneCharInputStream replayStream;

    private final InputStreamReader replayReader;

    public UnixTerminal() throws Exception {
        super(true);

        this.replayStream = new ReplayPrefixOneCharInputStream(Configuration.getInputEncoding());
        this.replayReader = new InputStreamReader(replayStream, replayStream.getEncoding());
    }

    protected TerminalLineSettings getSettings() {
        return settings;
    }

    /**
     * Remove line-buffered input by invoking "stty -icanon min 1"
     * against the current terminal.
     */
    @Override
    public void init() throws Exception {
        super.init();

        setAnsiSupported(true);

        // set the console to be character-buffered instead of line-buffered
        settings.set("-icanon min 1");

        setEchoEnabled(false);
    }

    /**
     * Restore the original terminal configuration, which can be used when
     * shutting down the console reader. The ConsoleReader cannot be
     * used after calling this method.
     */
    @Override
    public void restore() throws Exception {
        settings.restore();
        super.restore();
        // print a newline after the terminal exits.
        // this should probably be a configurable.
        System.out.println();
    }

    /**
     * Returns the value of <tt>stty columns</tt> param.
     */
    @Override
    public int getWidth() {
        int w = settings.getProperty("columns");
        return w < 1 ? DEFAULT_WIDTH : w;
    }

    /**
     * Returns the value of <tt>stty rows>/tt> param.
     */
    @Override
    public int getHeight() {
        int h = settings.getProperty("rows");
        return h < 1 ? DEFAULT_HEIGHT : h;
    }

    @Override
    public synchronized void setEchoEnabled(final boolean enabled) {
        try {
            if (enabled) {
                settings.set("echo");
            }
            else {
                settings.set("-echo");
            }
            super.setEchoEnabled(enabled);
        }
        catch (Exception e) {
            Log.error("Failed to ", (enabled ? "enable" : "disable"), " echo: ", e);
        }
    }

    @Override
    public int readVirtualKey(final InputStream in) throws IOException {
        int c = readCharacter(in);

        if (Key.valueOf(c) == DELETE && settings.getProperty("erase") == DELETE.code) {
            c = BACKSPACE.code;
        }

        UnixKey key = UnixKey.valueOf(c);

        // in Unix terminals, arrow keys are represented by a sequence of 3 characters. E.g., the up arrow key yields 27, 91, 68
        if (key == ARROW_START) {
            // also the escape key is 27 thats why we read until we have something different than 27
            // this is a bugfix, because otherwise pressing escape and than an arrow key was an undefined state
            while (key == ARROW_START) {
                c = readCharacter(in);
                key = UnixKey.valueOf(c);
            }

            if (key == ARROW_PREFIX || key == O_PREFIX) {
                c = readCharacter(in);
                key = UnixKey.valueOf(c);

                if (key == ARROW_UP) {
                    return CTRL_P.code;
                }
                else if (key == ARROW_DOWN) {
                    return CTRL_N.code;
                }
                else if (key == ARROW_LEFT) {
                    return CTRL_B.code;
                }
                else if (key == ARROW_RIGHT) {
                    return CTRL_F.code;
                }
                else if (key == HOME_CODE) {
                    return CTRL_A.code;
                }
                else if (key == END_CODE) {
                    return CTRL_E.code;
                }
                else if (key == DEL_THIRD) {
                    readCharacter(in); // read 4th & ignore
                    return DELETE.code;
                }
            }
            else if (c == 'b') { // alt-b: go back a word
                return CTRL_O.code; // PREV_WORD
            }
            else if (c == 'f') { // alt-f: go forward a word
                return CTRL_T.code; // NEXT_WORD
            }
            else if (key == DEL) { // alt-backspace: delete previous word
                return CTRL_W.code; // DELETE_PREV_WORD
            }
            else if (c == 'd') { // alt-d: delete next word
                return CTRL_X.code; // DELETE_NEXT_WORD
            }

        }

        // handle unicode characters, thanks for a patch from amyi@inf.ed.ac.uk
        if (c > 128) {
            // handle unicode characters longer than 2 bytes,
            // thanks to Marc.Herbert@continuent.com
            replayStream.setInput(c, in);
            // replayReader = new InputStreamReader(replayStream, encoding);
            c = replayReader.read();
        }

        return c;
    }

    /**
     * Unix keys.
     */
    public static enum UnixKey
    {
        ARROW_START(27),

        ARROW_PREFIX(91),

        ARROW_LEFT(68),

        ARROW_RIGHT(67),

        ARROW_UP(65),

        ARROW_DOWN(66),

        O_PREFIX(79),

        HOME_CODE(72),

        END_CODE(70),

        DEL_THIRD(51),

        DEL_SECOND(126),

        DEL(127);


        public final short code;

        UnixKey(final int code) {
            this.code = (short) code;
        }

        private static final Map<Short, UnixKey> codes;

        static {
            Map<Short, UnixKey> map = new HashMap<Short, UnixKey>();

            for (UnixKey key : UnixKey.values()) {
                map.put(key.code, key);
            }

            codes = map;
        }

        public static UnixKey valueOf(final int code) {
            return codes.get((short) code);
        }
    }
}