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/*
 * Copyright 2003-2009 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.codehaus.groovy.reflection;

import org.objectweb.asm.Opcodes;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.ClassReader;

import java.util.Map;
import java.util.HashMap;
import java.io.IOException;
import java.io.InputStream;
import java.security.AccessController;
import java.security.PrivilegedAction;

/**
 * Special class loader, which when running on Sun VM allows to generate accessor classes for any method
 */
public class SunClassLoader extends ClassLoader implements Opcodes {
    protected final Map knownClasses = new HashMap();

    protected static final SunClassLoader sunVM;

    static {
        SunClassLoader res;
        try {
            res = AccessController.doPrivileged(new PrivilegedAction() {
                public SunClassLoader run() {
                    try {
                        return new SunClassLoader();
                    } catch (Throwable e) {
                        return null;
                    }
                }
            });
        }
        catch (Throwable e) {
            res = null;
        }
        sunVM = res;
    }

    protected SunClassLoader() throws Throwable {
        super (SunClassLoader.class.getClassLoader());

        final Class magic = ClassLoader.getSystemClassLoader().loadClass("sun.reflect.MagicAccessorImpl");
        knownClasses.put("sun.reflect.MagicAccessorImpl", magic);
        loadMagic ();
    }

    private void loadMagic() {
        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
        cw.visit(Opcodes.V1_4, Opcodes.ACC_PUBLIC, "sun/reflect/GroovyMagic", null, "sun/reflect/MagicAccessorImpl", null);
        MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, "sun/reflect/MagicAccessorImpl", "", "()V");
        mv.visitInsn(RETURN);
        mv.visitMaxs(0,0);
        mv.visitEnd();
        cw.visitEnd();

        define(cw.toByteArray(), "sun.reflect.GroovyMagic");
    }

    protected void loadFromRes(String name) throws IOException {
        final InputStream asStream = SunClassLoader.class.getClassLoader().getResourceAsStream(resName(name));
        ClassReader reader = new ClassReader(asStream);
        final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
        reader.accept(cw, ClassWriter.COMPUTE_MAXS);
        asStream.close();
        define(cw.toByteArray(), name);
    }

    protected static String resName(String s) {
        return s.replace('.','/') + ".class";
    }

    protected void define(byte[] bytes, final String name) {
        knownClasses.put(name, defineClass(name, bytes, 0, bytes.length));
    }

    protected synchronized Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
        final Class aClass = knownClasses.get(name);
        if (aClass != null)
          return aClass;
        else {
            try {
                return super.loadClass(name, resolve);
            }
            catch (ClassNotFoundException e) {
                return getClass().getClassLoader().loadClass(name);
            }
        }
    }

    public Class doesKnow(String name) {
        return knownClasses.get(name);
    }
}