net.afterchat.mocap.MocapClassTransformer.java Source code

Introduction

Here is the source code for net.afterchat.mocap.MocapClassTransformer.java

Source

/**
 * The Mocap mod is a Minecraft mod aimed at film-makers who wish to
 * record the motion of their character and replay it back via a scripted
 * entity. It allows you to create a whole series of composite characters
 * for use in your own videos without having to splash out on extra accounts
 * or enlist help.
 * 
 * Copyright (C) 2013-2014 Echeb Keso
 *
 * This program 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.*
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */

package net.afterchat.mocap;

import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.ASTORE;
import static org.objectweb.asm.Opcodes.DUP;
import static org.objectweb.asm.Opcodes.GETSTATIC;
import static org.objectweb.asm.Opcodes.ILOAD;
import static org.objectweb.asm.Opcodes.INVOKESPECIAL;
import static org.objectweb.asm.Opcodes.INVOKEVIRTUAL;
import static org.objectweb.asm.Opcodes.NEW;
import static org.objectweb.asm.Opcodes.POP;
import static org.objectweb.asm.Opcodes.RETURN;

import java.util.Iterator;

import net.minecraft.launchwrapper.IClassTransformer;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.FieldInsnNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.InsnNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.TypeInsnNode;
import org.objectweb.asm.tree.VarInsnNode;

public class MocapClassTransformer implements IClassTransformer {
    private static final Logger logger = LogManager.getLogger();

    @Override
    public byte[] transform(String arg0, String arg1, byte[] arg2) {

        /* Release Obf class */
        if (arg0.equals("aji")) {
            logger.info("** MOCAP - Injecting new event trigger into 'Block' Class : " + arg0);
            return patchClassASM(arg0, arg2);
        }

        /* Debug class */
        if (arg0.equals("net.minecraft.block.Block")) {
            logger.info("** MOCAP - Injecting new event trigger into 'Block' Class : " + arg0);
            return patchClassASM(arg0, arg2);
        }
        return arg2;
    }

    public byte[] patchClassASM(String name, byte[] bytes) {
        ClassNode classNode = new ClassNode();
        ClassReader classReader = new ClassReader(bytes);
        classReader.accept(classNode, 0);
        Iterator<MethodNode> methods = classNode.methods.iterator();

        while (methods.hasNext()) {
            MethodNode m = methods.next();

            if ((m.name.equals("onBlockPlacedBy"))
                    || (m.name.equals("a") && m.desc.equals("(Lahb;IIILsv;Ladd;)V"))) {
                logger.info("** MOCAP - Patching onBlockPlacedBy: " + m.name);
                AbstractInsnNode currentNode = null;
                Iterator<AbstractInsnNode> iter = m.instructions.iterator();
                int index = -1;

                while (iter.hasNext()) {
                    index++;
                    currentNode = iter.next();

                    /**
                     * Just prior to the original empty function return, inject code to trigger
                     * our custom block place event.
                     */
                    if (currentNode.getOpcode() == RETURN) {
                        InsnList toInject = new InsnList();
                        toInject.add(new TypeInsnNode(NEW, "net/afterchat/mocap/LivingPlaceBlockEvent"));
                        toInject.add(new InsnNode(DUP));
                        toInject.add(new VarInsnNode(ALOAD, 5));
                        toInject.add(new VarInsnNode(ALOAD, 6));
                        toInject.add(new VarInsnNode(ILOAD, 2));
                        toInject.add(new VarInsnNode(ILOAD, 3));
                        toInject.add(new VarInsnNode(ILOAD, 4));
                        toInject.add(new MethodInsnNode(INVOKESPECIAL, "net/afterchat/mocap/LivingPlaceBlockEvent",
                                "<init>",
                                "(Lnet/minecraft/entity/EntityLivingBase;Lnet/minecraft/item/ItemStack;III)V"));
                        toInject.add(new VarInsnNode(ASTORE, 7));
                        toInject.add(new FieldInsnNode(GETSTATIC, "net/minecraftforge/common/MinecraftForge",
                                "EVENT_BUS", "Lcpw/mods/fml/common/eventhandler/EventBus;"));
                        toInject.add(new VarInsnNode(ALOAD, 7));
                        toInject.add(new MethodInsnNode(INVOKEVIRTUAL, "cpw/mods/fml/common/eventhandler/EventBus",
                                "post", "(Lcpw/mods/fml/common/eventhandler/Event;)Z"));
                        toInject.add(new InsnNode(POP));

                        m.instructions.insertBefore(currentNode, toInject);
                    }
                }
            }
        }

        ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
        classNode.accept(writer);
        return writer.toByteArray();
    }
}