VanillaGenerationClassFactory.java

/*
 *  Copyright (c) 2014, Lukas Tenbrink.
 *  * http://lukas.axxim.net
 */

package ivorius.reccomplex.worldgen.villages;

import com.google.common.collect.BiMap;
import com.google.common.collect.HashBiMap;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Type;

import java.util.HashSet;
import java.util.Set;

import static org.objectweb.asm.Opcodes.*;

/**
 * Created by lukas on 26.03.15.
 */
public class VanillaGenerationClassFactory extends ClassLoader
{
    private static final VanillaGenerationClassFactory INSTANCE = new VanillaGenerationClassFactory();

    protected Set<String> failed = new HashSet<>();

    public static VanillaGenerationClassFactory instance()
    {
        return INSTANCE;
    }

    public Class<?> define(String name, byte[] data)
    {
        return defineClass(name, data, 0, data.length);
    }

    public Class<? extends GenericVillagePiece> getClass(String structureID)
    {
        try
        {
            return (Class<? extends GenericVillagePiece>) findClass(classNameForStructure(structureID));
        }
        catch (ClassNotFoundException ignored)
        {
        }

        if (!failed.contains(structureID))
        {
            Class<? extends GenericVillagePiece> created = createClass(structureID);
            if (created == null)
                failed.add(structureID);
            return created;
        }

        return null;
    }

    protected Class<? extends GenericVillagePiece> createClass(String structureID)
    {
        try
        {
            return (Class<? extends GenericVillagePiece>) define(classNameForStructure(structureID), createClassBinary(structureID));
        }
        catch (Exception ex)
        {
            return null;
        }
    }

    protected String classNameForStructure(String structureID)
    {
        return "ivorius/reccomplex/dynamic/vanillagen/" + structureID;
    }

    protected byte[] createClassBinary(String className)
    {
        ClassWriter cw = new ClassWriter(0);
        cw.visit(V1_5, ACC_PUBLIC, className, null, Type.getInternalName(GenericVillagePiece.class), null);

        {
            // constructor
            MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
            mv.visitMaxs(2, 1);
            mv.visitVarInsn(ALOAD, 0);
            mv.visitMethodInsn(INVOKESPECIAL, Type.getInternalName(Object.class), "<init>", "()V", false);
            mv.visitInsn(RETURN);
            mv.visitEnd();
        }
        {
            // public Object get() { return new Object(); }
            MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "get", "()Ljava/lang/Object;", null, null);
            mv.visitMaxs(2, 1);
            mv.visitTypeInsn(NEW, Type.getInternalName(Object.class));
            mv.visitInsn(DUP);
            mv.visitMethodInsn(INVOKESPECIAL, Type.getInternalName(Object.class), "<init>", "()V", false);
            mv.visitInsn(ARETURN);
            mv.visitEnd();
        }
        cw.visitEnd();

        return cw.toByteArray();
    }
}