content: /**
   * This file is part of Aion-Lightning <aion-lightning.org>.
   *
   *  Aion-Lightning 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.
   *
   *  Aion-Lightning 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 Aion-Lightning.
   *  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package com.aionemu.commons.callbacks.enhancer;
  
  import java.lang.instrument.ClassFileTransformer;
  import java.lang.instrument.IllegalClassFormatException;
  import java.security.ProtectionDomain;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.aionemu.commons.utils.ExitCode;
  
  /**
   * Basic class that checks if class can be transformed. JDK classes are not a
   * subject of transformation.
   *
   * @author SoulKeeper
   */
  public abstract class CallbackClassFileTransformer implements ClassFileTransformer {
  
  	private static final Logger log = LoggerFactory.getLogger(CallbackClassFileTransformer.class);
  
  	/**
  	 * This method analyzes class and adds callback support if needed.
  	 *
  	 * @param loader
  	 *            ClassLoader of class
  	 * @param className
  	 *            class name
  	 * @param classBeingRedefined
  	 *            not used
  	 * @param protectionDomain
  	 *            not used
  	 * @param classfileBuffer
  	 *            basic class data
  	 */
  	@Override
  	public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
  			ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
  		try {
  			// no need to scan whole jvm boot classpath
  			// also there is no need to transform classes from jvm 'ext' dir
  			if (loader == null || loader.getClass().getName().equals("sun.misc.Launcher$ExtClassLoader")) {
  				log.trace("Class " + className + " ignored.");
  				return null;
  			}
  
  			// actual class transformation
  			return transformClass(loader, classfileBuffer);
  		} catch (Exception e) {
  
  			Error e1 = new Error("Can't transform class " + className, e);
  			log.error(e1.getMessage(), e1);
  
  			// if it is a class from core (not a script) - terminate server
  			// noinspection ConstantConditions
  			if (loader != null && loader.getClass().getName().equals("sun.misc.Launcher$AppClassLoader")) {
  				Runtime.getRuntime().halt(ExitCode.CODE_ERROR);
  			}
  
  			throw e1;
  		}
  	}
  
  	/**
  	 * Actually transforms the class.
  	 *
  	 * @param loader
  	 *            class loader of this class
  	 * @param clazzBytes
  	 *            class bytes
  	 * @return class as byte array if was transformed or null if was not
  	 * @throws Exception
  	 *             if something went wrong
  	 */
  	protected abstract byte[] transformClass(ClassLoader loader, byte[] clazzBytes) throws Exception;
  }
  