gnu.jel.ImageLoader Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jgt-oms3 Show documentation
There is a newer version: 0.8.1
/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * $Id: ImageLoader.java 491 2007-10-12 17:25:56Z metlov $
 *
 * This file is part of the Java Expressions Library (JEL).
 *   For more information about JEL visit :
 *    http://kinetic.ac.donetsk.ua/JEL/
 *
 * (c) 1998 -- 2007 by Konstantin Metlov([email protected]);
 *
 * JEL is Distributed under the terms of GNU General Public License.
 *    This code comes with ABSOLUTELY NO WARRANTY.
 *  For license details see COPYING file in this directory.
 */

package gnu.jel;
import gnu.jel.debug.Debug;

/**
 * Loads JEL-generated classes into Java VM.
 *  Specifics of JEL generated classes is that the class name UTF8 is always
 * the first entry in the constant pool. This loader will not load 
 * other classes.
 */
public class ImageLoader extends ClassLoader {
  String name;
  byte[] bytes;
  Class c;
  ClassLoader parent;
  
  private ImageLoader(String name, byte[] bytes) {
    this.name=name;
    this.bytes=bytes;
    this.c=null;
    this.parent=this.getClass().getClassLoader();
  };
  

  /**
   * Loads given JEL-generated image under its own name.
   * @param image to load
   * @return the class object for the new class or null 
   *         if unsuccessful.
   */
  public static Class load(byte[] image) {
    if (Debug.enabled)
      Debug.check(image[10]==1,
                   "Attempt to load non-JEL generated class file");
      
    // JEL generated class file never have UNICODE class name
    // although they might reference UNICODE methods, etc...
    int len=(image[11]<<8)+image[12];
    char[] nameChr=new char[len];
    for(int i=0;i"load" below) if You have an older version
//    // of JDK (below 1.1.7, AFAIK), which does not allow classes with
//    // the _same_ names to be loaded by _different_ classloaders.
//    //
//    // Number of loaded expressions in this session
//    private transient volatile static long expressionUID=0;

//    /**
//     * Prefix of the expression classname
//     * 
Example: "gnu.jel.generated.E_"
//     */
//    public static String classNamePrefix="gnu.jel.generated.E_";

//    /**
//     * Loads given JEL-generated image under unique name.
//     * 
The unique name is generated by appending a steadily incremented
//     * number to the classNamePrefix.
//     * @param image to load
//     * @return the class object for the new class or null 
//     *         if unsuccessful.
//     * @see gnu.jel.ImageLoader#classNamePrefix
//     */
//    public static Class loadRenamed(byte[] image) {
//      if (Debug.enabled)
//        Debug.check(image[10]==1,
//                     "Attempt to load non-JEL generated class file");

//      String newname=classNamePrefix+Long.toString(expressionUID++);
//      String newnameHF=TypesStack.toHistoricalForm(newname);

//      // JEL generated class file never have UNICODE class name
//      // although they might reference UNICODE methods, etc...
//      int len=(image[11]<<8)+image[12];
//      int newlen=newname.length();
    
//      byte[] newimage=new byte[image.length-len+newlen];
    
//      System.arraycopy(image,0,newimage,0,11);
//      newimage[11]=(byte)(newlen>>8);
//      newimage[12]=(byte)newlen;
//      for(int i=0;i