Code

EDClassTransformer.java

package com.rubisk.colorsignmod;

import java.util.Iterator;

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.MethodNode;
import static org.objectweb.asm.Opcodes.SIPUSH;
import net.minecraft.launchwrapper.IClassTransformer;

public class EDClassTransformer implements IClassTransformer {

	@Override
	public byte[] transform(String arg0, String arg1, byte[] arg2) {
	//Bytecode manipulations goes here
		if (arg0.equals("v")){
			System.out.println("***PATCHING " + arg0 + " IN OBFUSCATED TRANSFORMER***");
			return patchClassASM(arg0, arg2, true);
		}

		if (arg0.equals("net.minecraft.util.ChatAllowedCharacters")){
			System.out.println("***PATCHING " + arg0 + " IN TRANSFORMER***");
			return patchClassASM(arg0, arg2, false);

		}
		return arg2;

	}

	public byte[] patchClassASM(String name, byte[] bytes, boolean obfuscated) {

		String targetMethodName = "";

		//Our target method
		if(obfuscated == true)
			targetMethodName ="a";
		else
			targetMethodName ="isAllowedCharacter";


		//set up ASM class manipulation stuff. Consult the ASM docs for details
		ClassNode classNode = new ClassNode();
		ClassReader classReader = new ClassReader(bytes);
		classReader.accept(classNode, 0);

		//Now we loop over all of the methods declared inside the Explosion class until we get to the targetMethodName "doExplosionB"
		Iterator<MethodNode> methods = classNode.methods.iterator();
		while(methods.hasNext()){

			MethodNode m = methods.next();
			int fdiv_index = -1;
			System.out.println(m.name);
			//Check if this is doExplosionB and it's method signature is (Z)V which means that it accepts a boolean (Z) and returns a void (V)
			if ((m.name.equals(targetMethodName) && m.desc.equals("(C)Z"))){
				System.out.println("********* Inside target method!");

					AbstractInsnNode currentNode = null;
					AbstractInsnNode targetNode = null;

					@SuppressWarnings("unchecked")
					Iterator<AbstractInsnNode> iter = m.instructions.iterator();

					int index = -1;

					//Loop over the instruction set and find the instruction FDIV which checks for 167
					while (iter.hasNext()){
						index++;
						currentNode = iter.next();

						//Found it! save the index location of instruction FDIV and the node for this instruction
						if (currentNode.getOpcode() == SIPUSH){
							targetNode = currentNode;
							fdiv_index = index;
						}
					}

					//now we want the save nods that load the variable explosionSize and the division instruction:

					/*
					mv.visitInsn(FCONST_1);
					mv.visitVarInsn(ALOAD, 0);
					mv.visitFieldInsn(GETFIELD, "net/minecraft/src/Explosion", "explosionSize", "F");
					mv.visitInsn(FDIV);
					mv.visitInsn(ICONST_0);
					mv.visitMethodInsn(INVOKEVIRTUAL, "net/minecraft/src/Block", "dropBlockAsItemWithChance", "(Lnet/minecraft/src/World;IIIIFI)V");
					*/

					AbstractInsnNode remNode1 = m.instructions.get(fdiv_index+1); // mv.visitFieldInsn(GETFIELD, "net/minecraft/src/Explosion", "explosionSize", "F");
					AbstractInsnNode remNode2 = m.instructions.get(fdiv_index-1); // mv.visitFieldInsn(GETFIELD, "net/minecraft/src/Explosion", "explosionSize", "F");
					AbstractInsnNode remNode3 = m.instructions.get(fdiv_index); // mv.visitInsn(FDIV);


					//just remove these nodes from the instruction set, this will prevent the instruction FCONST_1 to be divided.

					m.instructions.remove(remNode1);
					m.instructions.remove(remNode2);
					m.instructions.remove(remNode3);


					//in this section, i'll just illustrate how to inject a call to a static method if your instruction is a little more advanced than just removing a couple of instruction:

					/*
					To add new instructions, such as calling a static method can be done like so:

					// make new instruction list
					InsnList toInject = new InsnList();

					//add your own instruction lists: *USE THE ASM JAVADOC AS REFERENCE*
					toInject.add(new VarInsnNode(ALOAD, 0));
					toInject.add(new MethodInsnNode(INVOKESTATIC, "mod/culegooner/MyStaticClass", "myStaticMethod", "()V"));

					// add the added code to the nstruction list
					// You can also choose if you want to add the code before or after the target node, check the ASM Javadoc (insertBefore)
					m.instructions.insert(targetNode, toInject);
					*/

					System.out.println("Patching Complete!");
					break;
				}
			}

		//ASM specific for cleaning up and returning the final bytes for JVM processing.
		ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
		classNode.accept(writer);
		return writer.toByteArray();
		}
}

EDFMLLoadingPlugin.java

package com.rubisk.colorsignmod;

import java.util.Map;

import net.minecraftforge.fml.relauncher.IFMLLoadingPlugin;

public class EDFMLLoadingPlugin implements IFMLLoadingPlugin {

	@Override
	public String[] getASMTransformerClass() {
	//This will return the name of the class "com.rubisk.EDClassTransformer"
	return new String[]{EDClassTransformer.class.getName()};
	}

	@Override
	public String getModContainerClass() {
		//This is the name of our dummy container "mod.culegooner.CreeperBurnCore.CBDummyContainer"
		return MyContainer.class.getName();
	}

	@Override
	public String getSetupClass() {
		return null;
	}

	@Override
	public void injectData(Map<String, Object> data) {
	}

	@Override
	public String getAccessTransformerClass() {
		return null;
	}
}

MyContainer.java

package com.rubisk.colorsignmod;

import java.util.Arrays;

import net.minecraftforge.fml.common.LoadController;
import net.minecraftforge.fml.common.ModMetadata;
import net.minecraftforge.fml.common.event.FMLConstructionEvent;
import net.minecraftforge.fml.common.event.FMLInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPostInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;

import com.google.common.eventbus.EventBus;
import com.google.common.eventbus.Subscribe;

public class MyContainer extends net.minecraftforge.fml.common.DummyModContainer {

	public MyContainer() {

	super(new ModMetadata());
	ModMetadata meta = getMetadata();
	meta.modId = "ColorSignMod";
	meta.name = "Colored Section Signs Allowance";
	meta.version = "1.0";
	meta.credits = "";
	meta.authorList = Arrays.asList("Rubisk_");
	meta.description = "";
	meta.url = "";
	meta.updateUrl = "";
	meta.screenshots = new String[0];
	meta.logoFile = "";

	}

	@Override
	public boolean registerBus(EventBus bus, LoadController controller) {
		bus.register(this);
		return true;
	}

	@Subscribe
	public void modConstruction(FMLConstructionEvent evt){
	}

	@Subscribe
	public void preInit(FMLPreInitializationEvent evt) {
	}

	@Subscribe
	public void init(FMLInitializationEvent evt) {
	}


	@Subscribe
	public void postInit(FMLPostInitializationEvent evt) {
	}

}