com.l2jfree.loginserver.L2LoginIdentifier.java Source code

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Here is the source code for com.l2jfree.loginserver.L2LoginIdentifier.java

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/*
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <http://www.gnu.org/licenses/>.
 */
package com.l2jfree.loginserver;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

import org.apache.commons.io.IOUtils;

import com.l2jfree.util.Rnd;
import com.l2jfree.util.logging.L2Logger;

/**
 * The purpose of this class is classified. <BR>
 * <BR>
 * Pun intended.
 * 
 * @author savormix
 */
public final class L2LoginIdentifier {
    private static final L2Logger _log = L2Logger.getLogger(L2LoginIdentifier.class);
    private static final String FILENAME = ".l2jfree-ls";

    private long _uid;
    private boolean _loaded;

    private L2LoginIdentifier() {
        _uid = 0;
        _loaded = false;
    }

    /**
     * Returns the unique identifier for this login server.
     * 
     * @return unique identifier
     */
    public long getUID() {
        if (!isLoaded())
            load();
        return _uid;
    }

    private synchronized void load() {
        if (isLoaded())
            return;

        File f = new File(System.getProperty("user.home", null), FILENAME);
        ByteBuffer bb = ByteBuffer.allocateDirect(8);

        if (!f.exists() || f.length() != 8) {
            _uid = getRandomUID();
            _loaded = true;
            _log.info("A new UID has been generated for this login server.");

            FileOutputStream fos = null;
            try {
                f.createNewFile();
                fos = new FileOutputStream(f);
                FileChannel fc = fos.getChannel();
                bb.putLong(getUID());
                bb.flip();
                fc.write(bb);
                fos.flush();
            } catch (IOException e) {
                _log.warn("Could not store login server's UID!", e);
            } finally {
                IOUtils.closeQuietly(fos);
                f.setReadOnly();
            }
        } else {
            FileInputStream fis = null;
            try {
                fis = new FileInputStream(f);
                FileChannel fc = fis.getChannel();
                fc.read(bb);
            } catch (IOException e) {
                _log.warn("Could not read stored login server's UID!", e);
            } finally {
                IOUtils.closeQuietly(fis);
            }

            if (bb.position() > 0) {
                bb.flip();
                _uid = bb.getLong();
            } else
                _uid = getRandomUID();
            _loaded = true;
        }
    }

    private static long getRandomUID() {
        return Rnd.nextLong();
    }

    private boolean isLoaded() {
        return _loaded;
    }

    /**
     * Returns a singleton object.
     * 
     * @return an instance of this class
     */
    public static L2LoginIdentifier getInstance() {
        return SingletonHolder.INSTANCE;
    }

    private static final class SingletonHolder {
        public static final L2LoginIdentifier INSTANCE = new L2LoginIdentifier();
    }
}