[1.7.2] Patching a vanilla method does not work

CreativeMD · May 12, 2014

Hi,

I read this tutorial: here

I don't understand everything, so please don't blame me i'm stupid . I just thought this could work.

I want to replace this:

public void doRender(Entity par1Entity, double par2, double par4, double par6, float par8, float par9)
    {
        this.doRender((EntityItem)par1Entity, par2, par4, par6, par8, par9);
    }

with this

ItemDummyContainer.doRender((EntityItem)par1Entity, par2, par4, par6, par8, par9, renderInFrame, renderWithColor);

So for this i used this method:

@Override
public byte[] transform(String arg0, String arg1, byte[] arg2) {
	if (arg0.contains("net.minecraft.client.renderer.entity.RenderItem")) {
		System.out.println("********* INSIDE OBFUSCATED MINECRAFTLOADER TRANSFORMER ABOUT TO PATCH: " + arg0);
		arg2 = replaceMethod(arg0, arg2, ItemPatchingLoader.location, !arg0.contains("net.minecraft.client.renderer.entity.RenderItem"));
		return arg2;
	}

public byte[] replaceMethod(String name, byte[] bytes, File location, boolean obfuscated)
{
	String targetMethodName = "doRender";


	//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);

	Iterator<MethodNode> methods = classNode.methods.iterator();
	while(methods.hasNext())
	{
		MethodNode m = methods.next();

		if ((m.name.equals(targetMethodName) && m.desc.equals("(Lnet/minecraft/entity/Entity;DDDFF)V")))
		{
			System.out.println("********* Inside target method!");

			AbstractInsnNode currentNode = null;

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

			int index = -1;

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

				//Found it! save the index location of instruction FDIV and the node for this instruction
				if (currentNode instanceof MethodInsnNode)
				{
					m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETSTATIC, name, "renderInFrame", "Z"));
					m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETFIELD, name, "renderWithColor", "Z"));
					((MethodInsnNode) currentNode).desc = "(Lnet/minecraft/entity/item/EntityItem;DDDFFZZ)V";
					((MethodInsnNode) currentNode).owner = "com/creativemd/itemphysic/ItemDummyContainer";
					((MethodInsnNode) currentNode).setOpcode(INVOKESTATIC);
				}
			}

			m.visitEnd();
			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();
}

I just copy this code from the forum, but this part is programmed by myself:

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

				//Found it! save the index location of instruction FDIV and the node for this instruction
				if (currentNode instanceof MethodInsnNode)
				{
					m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETSTATIC, name, "renderInFrame", "Z"));
					m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETFIELD, name, "renderWithColor", "Z"));
					((MethodInsnNode) currentNode).desc = "(Lnet/minecraft/entity/item/EntityItem;DDDFFZZ)V";
					((MethodInsnNode) currentNode).owner = "com/creativemd/itemphysic/ItemDummyContainer";
					((MethodInsnNode) currentNode).setOpcode(INVOKESTATIC);
				}
			}

This inserts the new two fields (renderInFrame and renderWithColor) and changes the method.

Like a said, i don't understand everything with is going on, but obviously this don't work, because this error comes up:

java.lang.NoClassDefFoundError: net/minecraft/client/renderer/entity/RenderItem
...
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.renderer.entity.RenderItem

So hopefully i could give you an impression what is going on. I don't have an idea what is wrong.

I would be very very happy if someone can help me

EDIT

I noticed that when i let the new two booleans, out it works , so the error caused by the insertBefore. I noticed that my two new FieldInNode have an index of 0 and doesn't fit into it.

Thanks previously

CreativeMD · May 12, 2014

Oh man your so right , of course i know this renderer, but i didn't thought about it.

Anyways i have to do something similar again, so can you tell me what i'm doing wrong.

I found out that i have to change this

m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETFIELD, name, "renderWithColor", "Z"));

to this

m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETFIELD, name.replace(".", "/"), "renderWithColor", "Z"));

but then this error comes up

java.lang.VerifyError: (class: net/minecraft/client/renderer/entity/RenderItem, method: doRender signature: (Lnet/minecraft/entity/Entity;DDDFF)V) Expecting to find object/array on stack

I would be very happy if you could help me with that

CreativeMD · May 13, 2014

Basically i have no clue at all . I read the tutorial on replacing a vanilla method and start debugging the code and try to get an impression what is going on.

So i just look at all variables and thought this could work. Changing the method like this:

((MethodInsnNode) currentNode).desc = "(Lnet/minecraft/entity/item/EntityItem;DDDFF)V";
((MethodInsnNode) currentNode).owner = "com/creativemd/itemphysic/ItemDummyContainer";
((MethodInsnNode) currentNode).setOpcode(INVOKESTATIC);

does obviously work out . I installed a ByteCode plugin in my eclipse and look up how this method looks like. I recognized that the variables are "visited" before the method is called and after that they get an label like this

mv = cw.visitMethod(ACC_PUBLIC, "doRender", "(Lnet/minecraft/entity/Entity;DDDFF)V", null, null);
mv.visitCode();
Label l0 = new Label();
mv.visitLabel(l0);
mv.visitLineNumber(756, l0);
mv.visitVarInsn(ALOAD, 0);
mv.visitVarInsn(ALOAD, 1);
mv.visitTypeInsn(CHECKCAST, "net/minecraft/entity/item/EntityItem");
mv.visitVarInsn(DLOAD, 2);
mv.visitVarInsn(DLOAD, 4);
mv.visitVarInsn(DLOAD, 6);
mv.visitVarInsn(FLOAD, ;
mv.visitVarInsn(FLOAD, 9);
mv.visitMethodInsn(INVOKEVIRTUAL, "net/minecraft/client/renderer/entity/RenderItem", "doRender", "(Lnet/minecraft/entity/item/EntityItem;DDDFF)V", false);
Label l1 = new Label();
mv.visitLabel(l1);
mv.visitLineNumber(757, l1);
mv.visitInsn(RETURN);
Label l2 = new Label();
mv.visitLabel(l2);
mv.visitLocalVariable("this", "Lnet/minecraft/client/renderer/entity/RenderItem;", null, l0, l2, 0);
mv.visitLocalVariable("par1Entity", "Lnet/minecraft/entity/Entity;", null, l0, l2, 1);
mv.visitLocalVariable("par2", "D", null, l0, l2, 2);
mv.visitLocalVariable("par4", "D", null, l0, l2, 4);
mv.visitLocalVariable("par6", "D", null, l0, l2, 6);
mv.visitLocalVariable("par8", "F", null, l0, l2, ;
mv.visitLocalVariable("par9", "F", null, l0, l2, 9);
mv.visitMaxs(10, 10);
mv.visitEnd();

So i tried to add a new parameter to the method by just adding this

m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETFIELD, name.replace(".", "/"), "renderWithColor", "Z"));

But this obviously don't work, i just look into m.instructions variable and tried to do it the same way. Yes and of course i changed the desc to that "(Lnet/minecraft/entity/item/EntityItem;DDDFFZ)V", but it's still not working.

So hopefully this can help you to help me .

CreativeMD · May 13, 2014

You are completely right, but i found no tutorials .

I know this is difficulty because i understand only 20% of what is going on, because of that i looked into that code also in variables of the instructions, but this was obviously not enough .

So i would be very happy if you could give me a link to a tutorial and i also would be very happy if you could tell me why this is not working, isn't their a possibility to add instructions?

Probably you don't understand it because you don't have enough information

CreativeMD · May 13, 2014

m.instructions.insertBefore(currentNode, new VarInsnNode(ALOAD, 0)); //mv.visitVarInsn(ALOAD, 0);
m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETFIELD, name.replace(".", "/"), "renderWithColor", "Z"));
((MethodInsnNode) currentNode).desc = "(Lnet/minecraft/entity/item/EntityItem;DDDFFZ)V";
((MethodInsnNode) currentNode).owner = "com/creativemd/itemphysic/ItemDummyContainer";
((MethodInsnNode) currentNode).setOpcode(INVOKESTATIC);

i only need to add this line , thank you very much. If this would be a getstatic this line before is not needed.

CreativeMD · May 15, 2014

I'm sad to tell this, but there is new error.

My Code

public byte[] replaceMethod(String name, byte[] bytes, File location, boolean obfuscated)
{
	String targetMethodName = "doRender";
	String targetDESC = "(Lnet/minecraft/entity/Entity;DDDFF)V";
	String newDESC = "(Lnet/minecraft/entity/Entity;DDDFFZ)V";
	String targetVar = "renderWithColor";

	//Our target method
	if(obfuscated == true)
	{
		System.out.println("Obfuscated");
		targetMethodName ="a";
		targetDESC = "(Lqn;DDDFF)V";
		newDESC = "(Lqn;DDDFFZ)V";
		targetVar = "field_77024_a";
	}


	//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);

	Iterator<MethodNode> methods = classNode.methods.iterator();
	while(methods.hasNext())
	{
		MethodNode m = methods.next();
		System.out.println("Search in " + m.name + ": " + m.desc);
		if ((m.name.equals(targetMethodName) && m.desc.equals(targetDESC)))
		{
			System.out.println("********* Inside target method!");

			AbstractInsnNode currentNode = null;

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

			while (iter.hasNext())
			{
				currentNode = iter.next();
				if (currentNode instanceof MethodInsnNode)
				{
					//m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETSTATIC, RenderItem.class.get, "renderInFrame", "Z"));
					m.instructions.insertBefore(currentNode, new VarInsnNode(ALOAD, 0)); //mv.visitVarInsn(ALOAD, 0);
					m.instructions.insertBefore(currentNode, new FieldInsnNode(Opcodes.GETFIELD, name.replace(".", "/"), targetVar, "Z"));
					((MethodInsnNode) currentNode).desc = newDESC;
					((MethodInsnNode) currentNode).owner = "com/creativemd/itemphysic/ItemDummyContainer";
					((MethodInsnNode) currentNode).setOpcode(INVOKESTATIC);
				}
			}
			m.visitEnd();
			System.out.println("Patching Complete!");
			break;
		}
	}
	System.out.println("Search in " + name);
	//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();
}

I tried to release this, but then this error comes up:

---- Minecraft Crash Report ----
// Quite honestly, I wouldn't worry myself about that.

Time: 15.05.14 15:28
Description: Initializing game

java.lang.NoClassDefFoundError: net/minecraft/client/renderer/entity/RenderItem
at net.minecraft.client.gui.achievement.GuiAchievement.<init>(SourceFile:29)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:454)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:813)
at net.minecraft.client.main.Main.main(SourceFile:103)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:134)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.renderer.entity.RenderItem
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:188)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 10 more
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: bpv
at org.objectweb.asm.ClassWriter.getCommonSuperClass(Unknown Source)
at org.objectweb.asm.ClassWriter.a(Unknown Source)
at org.objectweb.asm.Frame.a(Unknown Source)
at org.objectweb.asm.Frame.a(Unknown Source)
at org.objectweb.asm.MethodWriter.visitMaxs(Unknown Source)
at org.objectweb.asm.tree.MethodNode.accept(Unknown Source)
at org.objectweb.asm.tree.MethodNode.accept(Unknown Source)
at org.objectweb.asm.tree.ClassNode.accept(Unknown Source)
at com.creativemd.itemphysic.ItemTransformer.replaceMethod(ItemTra
nsformer.java:125)
at com.creativemd.itemphysic.ItemTransformer.transform(ItemTransformer.java:54)
at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:276)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:174)
... 12 more

I have no idea what is wrong

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[1.7.2] Patching a vanilla method does not work

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