fr.theshark34.feelcraft.FeelcraftClassTransformer.java Source code

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Here is the source code for fr.theshark34.feelcraft.FeelcraftClassTransformer.java

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/*
 * Copyright 2015 TheShark34
 * 
 * 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 fr.theshark34.feelcraft;

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.Opcodes;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;

/**
 * The Class Transformer - Inject a line that call the {@link Feelcraft} start
 * method in the startGame method in the Minecraft class.
 * 
 * @author TheShark34
 * @version 0.0.1-ALPHA
 */
public class FeelcraftClassTransformer implements IClassTransformer {

    /**
     * The Minecraft logger
     */
    private static final Logger logger = LogManager.getLogger();

    /**
     * Inject bytecode into the Minecraft class
     * 
     * @param name
     *            The class name
     * @param transformedName
     *            I don't really know what is this
     * @param basicClass
     *            The class bytes
     */
    @Override
    public byte[] transform(String name, String transformedName, byte[] basicClass) {

        // If the class name is bao (the Minecraft class obfuscated name)
        if (name.equals("bao"))
            // Patching the obfuscated game
            return patchClassASM(name, basicClass, true);

        // Else if the class name is net.minecraft.client.Minecraft
        else if (name.equals("net.minecraft.client.Minecraft"))
            // Patching the deobfuscated game
            return patchClassASM(name, basicClass, false);

        // Else return the given class
        return basicClass;
    }

    /**
     * Patchs the Minecraft class
     * 
     * @param name
     *            The class name
     * @param bytes
     *            The initial class bytes
     * @param obfuscated
     *            If the class is obfuscated
     * @return The modified bytes
     */
    public byte[] patchClassASM(String name, byte[] bytes, boolean obfuscated) {
        // Starting the pre init
        Feelcraft.preInit();

        // Printing messages
        logger.info("[Feelcraft] Starting patching Minecraft");
        logger.info("[Feelcraft] Target class : " + name);

        // Getting the target method if the game is obfuscated or not
        String targetMethod;
        if (obfuscated)
            targetMethod = "ag";
        else
            targetMethod = "startGame";

        // Getting the class nod and reading the initial class
        ClassNode classNode = new ClassNode();
        ClassReader classReader = new ClassReader(bytes);
        classReader.accept(classNode, 0);

        // Just a boolean that will be true if the patch will be done to check
        // if it was done
        boolean patchDone = false;

        // Getting the class methods
        Iterator<MethodNode> methods = classNode.methods.iterator();

        // For each method in the class
        while (methods.hasNext()) {
            // Getting the method
            MethodNode m = methods.next();

            // If the method is our target method
            if ((m.name.equals(targetMethod) && m.desc.equals("()V"))) {
                // Printing a message
                logger.info("[Feelcraft] Patching method : " + m.name + m.desc);

                // Insert a line that will call Feelcraft.start at the top of
                // the method
                m.instructions.insertBefore(m.instructions.getFirst(), new MethodInsnNode(Opcodes.INVOKESTATIC,
                        "fr/theshark34/feelcraft/Feelcraft", "start", "()V", false));

                // Setting patchDone to true
                patchDone = true;

                // Stopping the loop
                break;
            }
        }

        // If the patch wasn't done
        if (!patchDone)
            // Printing a warning message
            logger.warn("[Feelcraft] Warning the patch wasn't done ! Some things will not going to work !");

        // Writing the patched class
        logger.info("[Feelcraft] Writing the patched class");
        ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
        classNode.accept(writer);

        // Printing a done message
        if (patchDone)
            logger.info("[Feelcraft] Successfully patched Minecraft !");
        else
            logger.info("[Feelcraft] Done");

        // Returning the modified bytes
        return writer.toByteArray();
    }

}