classfilebuilder.java

JPC: x86 PC Hardware Emulator. 牛津大学开发的一个纯JAVA的x86系统结构硬件模拟器。

/*
    JPC: A x86 PC Hardware Emulator for a pure Java Virtual Machine
    Release Version 2.0

    A project from the Physics Dept, The University of Oxford

    Copyright (C) 2007 Isis Innovation Limited

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License version 2 as published by
    the Free Software Foundation.

    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, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
    Details (including contact information) can be found at: 

    www.physics.ox.ac.uk/jpc
*/

package org.jpc.emulator.memory.codeblock.fastcompiler;

import java.io.*;
import java.util.*;

import org.jpc.emulator.memory.codeblock.*;
import org.jpc.classfile.*;

import org.jpc.emulator.memory.codeblock.fastcompiler.real.RealModeSkeletonBlock;
import org.jpc.emulator.memory.codeblock.fastcompiler.prot.ProtectedModeSkeletonBlock;

public class ClassFileBuilder
{
    private static final int CLASSES_PER_LOADER = 10;

    private static final InputStream realModeSkeleton, protectedModeSkeleton;

    private static CustomClassLoader currentClassLoader;

    static 
    {
        realModeSkeleton = loadSkeletonClass(RealModeSkeletonBlock.class);
        protectedModeSkeleton = loadSkeletonClass(ProtectedModeSkeletonBlock.class);
        newClassLoader();
    }

    private static InputStream loadSkeletonClass(Class clz)
    {
        byte[] classBytes = null;
        String classRes = clz.getName().replace('.', '/')+".class";
        try 
        {
 	    ClassLoader cl = ClassFileBuilder.class.getClassLoader();
            if (cl == null)
                System.err.println("ClassFileBuilder failed to get the classloader.");
 	    InputStream in = cl.getResourceAsStream(classRes);

	    ByteArrayOutputStream bout = new ByteArrayOutputStream();
            
            while (true) {
                int ch = in.read();
                if (ch < 0)
                    break;
                bout.write((byte) ch);
            }
	    
            classBytes = bout.toByteArray();
        } 
        catch (Exception e) 
        {
            System.out.println("Exception reading in skeleton class " + clz + " into ClassFileBuilder: " + e);
        }
	
        return new ByteArrayInputStream(classBytes);
    }

    private ClassFileBuilder()
    {
    }

    public static ClassFile createNewRealModeSkeletonClass()
    {
        ClassFile cf = new ClassFile();
        
        try 
        {
            realModeSkeleton.reset();
            DataInputStream dis = new DataInputStream(realModeSkeleton);
            cf.read(dis);
        }
        catch (IOException e)
        {
            System.out.println("read error: " + e);
        }

        return cf;
    }

    public static ClassFile createNewProtectedModeSkeletonClass()
    {
        ClassFile cf = new ClassFile();
        
        try 
        {
            protectedModeSkeleton.reset();
            DataInputStream dis = new DataInputStream(protectedModeSkeleton);
            cf.read(dis);
        }
        catch (IOException e)
        {
            System.out.println("read error: " + e);
        }

        return cf;
    }

    public static CodeBlock instantiateClass(ClassFile cf)
    {
        cf.update();
        String className = cf.getClassName();

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        try 
        {           
            cf.write(new DataOutputStream(bos));
        }
        catch (IOException e)
        {
            System.out.println("write error: " + e);
        }
        catch (Exception e)
        {
            System.out.println("cb ic error: " + e);
        }

        byte[] classBytes = bos.toByteArray();
                
        Class codeBlockClass = currentClassLoader.createClass(className, classBytes, 0, classBytes.length);

        CodeBlock compiledBlock = null;
        try
        {
            compiledBlock = (CodeBlock) codeBlockClass.newInstance();
        }
        catch (InstantiationException e)
        {
            throw new IllegalStateException("Could not instantiate class", e);
        }
        catch (IllegalAccessException e)
        {
            throw new IllegalStateException("Could not instantiate class", e);
        }
        
        return compiledBlock;
    }

    private static void newClassLoader()
    {
	currentClassLoader = new CustomClassLoader();
    }

    static class CustomClassLoader extends ClassLoader
    {
	private Hashtable classes;
	private int classesCount;

	public CustomClassLoader()
	{
	    super(ClassFileBuilder.class.getClassLoader());
	    classes = new Hashtable();
	}

	public Class createClass(String name, byte[] b, int off, int len)
	{
	    if (++classesCount == CLASSES_PER_LOADER)
		newClassLoader();
	    
	    Class newClass = defineClass(name, b, off, len);
	    
	    classes.put(name, newClass);
	    
	    return newClass;
	}

	public Class findClass(String name) throws ClassNotFoundException
	{
	    Class myClass = (Class)classes.get(name);
	    if (myClass != null)
		return myClass;
	    else
		throw new ClassNotFoundException(name);
	}	
    }
}