Replacing base class

[sep87x]

Hey there,

 

I'm having some problems with a mod I'm working on. I want to rewrite the WorldGenDesertWells class so they become useful (seriously, they are pretty useless as they are now). As I finished and made the whole re-compile-obfuscate-blah procedure I recognized and remembered that it's impossible due to the new 1.6 update to replace base class files. Now I'm having a bit of a problem: I read a lot about ClassTransformers and stuff, but it didn't fit my imagination.

 

So my question is: is there any way to replace a whole vanilla class? The "new" class contains a new field, a (quiet huge) method and some changes in the generate() method. I do not own the original class file, because I've already edited it. Does anyone have an idea on how to do this? I am very close to release this mod and this is my last hurdle. I don't want to start the whole project all over again.

 

Greets from Germany

~ sep87x

[Mazetar]

possible but hard..

 

anyways wouldn't it be easier to replace every reference to that class with one to your own class. That at least sounds like less work if it's not called all over the place which it sounds like it ain't ?

[sep87x]

Okay, I removed a lot of code from the WorldGenDesertWells class and moved it into the main mod class. How should I progress further?

[Mazetar]

well I suggested moving it to it's own class. Since you where about to req. a few hundred byte code manipulations to change the whole class I figured you knew your java.

 

In any case it sounds quite extreme to do it like that, are you sure there aren't better ways to do the generation?

 

Also the base class thing not getting edited is possible to override for a mod if ya want to, but as always base class edited will possibly make your mod incompatible with other mods.

[sep87x]

  On 7/17/2013 at 10:45 AM, Mazetar said:

In any case it sounds quite extreme to do it like that, are you sure there aren't better ways to do the generation?

 

My current plan was to make the "custom" generation only one method in the main class to call, but diesieben07 had the better idea.

 

  Quote

How I would do it: Disable the vanilla WorldGenDesertWell by removing the override BiomeGenDesert.decorate via ASM (should be quite easy). That will stop the generation and then just generate a new type of well.

 

Thanks for that. Is there already an interface for that in Forge? I know I have to read something about ASM, but I already know a byte about it.

[sep87x]

Well, thanks. After I read your answer I found a very nice tutorial on ClassTransformers and such.

 

http://www.minecraftforum.net/topic/1854988-tutorial-162-changing-vanilla-without-editing-base-classes-coremods-and-events-very-advanced/

 

I'll try it now and come back if there are some other issues

[sep87x]

Okay, so I read through the whole thing and made the following: I set up a IClassTransformer which locates the decorate()-function inside the BiomeGenDesert class. With some byte code stuff I attempted to remove these lines:

 

            WorldGenDesertWells worldgendesertwells = new WorldGenDesertWells();
            worldgendesertwells.generate(par1World, par2Random, k, par1World.getHeightValue(k, l) + 1, l);

 

(Small amount of code, I hope it is okay to post it directly here)

 

... and make it to this:

 

            new FakeWorldGenDesertWells().generate(par1World, par2Random, k, par1World.getHeightValue(k, l) + 1, l);

 

I wrote it out and retrieved the byte code. My class transformer looks like this now: http://gw.minecraftforge.net/Ybvi

 

Before compiling, I have some questions left. Where do I need to register the class transformer and the FMLLoadingPlugin (onInit() should be clear, but which class is needed)? There are some other classes with the decorate()-method in it as I looked inside conf/methods. At the code it is now, should it be clear which method I want? I think "a" is a bit short ... even for a recompiled source.

[sep87x]

I'm sorry but I'm a bit confused now. I don't have an idea about coremods, so I need to ask. The DesertGenFMLLoadingPlugin (http://gw.minecraftforge.net/RBEG) class is the main class of the core mod. I've already "linked" the ClassTransformer in it. Do I need to add the name of the "original" mod in the method getModContainerClass(), so ModDesertWells.class.getName()? What does the manifest file look like? And I tried to add the argument (in program arguments) "fml.coreMods.load net.sep87x.desertwells.DesertGenFMLLoadingPlugin", but it didn't work. Am I doing something wrong?

[sep87x]

As far as I understood: I have two "main" classes now, the ModDesertWells class (\w @Mod annotation) and the DesertGenFMLLoadingPlugin (implements IFMLLoadingPlugin). Is it possible to "merge" both files? I mean if I can use the implementation in my ModDesertWells class? And ...

 

  On 7/17/2013 at 4:02 PM, sep87x said:

I tried to add the argument (in program arguments) "fml.coreMods.load net.sep87x.desertwells.DesertGenFMLLoadingPlugin", but it didn't work. Am I doing something wrong?

 

I am very sorry to ask so much. I'm new to coremods. Alternatively a link about coremods would be MUCH more appreciated. I couldn't find a page where coremods are being described.

[Mazetar]

The link you found above is more or less the only collection of info on coremods besides the source code

You can replace the ModDessertWells with the FMMLLoadingplugin class totally if you'd like, or use both as two seperate mods if you wish.

 

 

[sep87x]

I still don't get it. There must be something wrong when running MC. I removed the class with the @Mod annotation, moved anything to a ModContainer, and put the path into the gteModContainerClass() method of the FMLLoadingPlugin class. There must be something wrong with the running settings. I added the argument and added an environment variable.

 

 

 

I just don't get it. What am I doing wrong?

[sep87x]

Argh, me stupid

 

I added it to the vm args. Well, it recognizes the mod as a coremod, BUT there is another hurdle that popped up suddenly. There's a ClassNotFound exception in the package cpw.mods.fml.common.asm.FMLSanityChecker. See the full stack trace here: http://gw.minecraftforge.net/uPpv Is this normal?

 

My nerves are done for today. I guess I should wait for the next morning to come. Thanks to anyone who has helped me so far.

 

P.S. The class exists in the package explorer.

 

[sep87x]

I followed some instructions from the stack trace forum. That means I checked the class build path (everything alright) and checked the code where the exception has been created. I guess that something is wrong with my main coremod class (http://gw.minecraftforge.net/ufOJ), but I can't spot anything. It still raises the ClassNotFoundException (http://gw.minecraftforge.net/uPpv). Any ideas?

[sep87x]

Removed the import and the ModContainer already extends the DummyModContainer (http://gw.minecraftforge.net/89iA), but the error is still there. The class is existing, but when starting it acts like it is not existing anymore.

[sep87x]

Even with those two ideas it won't work. I'll just make a backup of my work, delete ANYTHING and create a new, fresh workspace.

[sep87x]

It really doesn't want to work. It's still a ClassNotFound exception. I'm out of ideas. The stack trace has changed a bit http://gw.minecraftforge.net/Ahpi

[sep87x]

java.lang.RuntimeException: java.lang.ClassNotFoundException: cpw.mods.fml.common.asm.FMLSanityChecker

 

Finally. I am not entirely sure, but I guess I found the source of the ClassNotFound error. As I read through the stack trace and searched for the path inside the jar, I couldn't find the common directory, the repackage and the server directory inside cpw/mods/fml. Might that be the source of the error? And what would be a way to fix this?

[BlueSpud]

I've gotten some ASM stuff to work, not replacing a whole class though. What I would assume you do is this:

(just pseudocode)

for the transformer, the transform method will be called for *I think* every class

byte[] transform(String name, byte[] bytes)
{
if (name == obfuscated name || name == deobfuscatedname)
{
   byte[] newClass = getYourClassBytes();
   return newClass;
}
}

The transform method kinda just goes through everything, see if you want to make changes, then asks for the modified or unmodified bytes back. You might be getting class not found because you aren't returning the bytes of the class.

[sep87x]

I've already dealt with that. The code should work as it is now (see here: http://gw.minecraftforge.net/hr4y). It returns the bytes correctly (of the target class), or am I missing something?

[BlueSpud]

  On 7/18/2013 at 6:32 PM, sep87x said:

I've already dealt with that. The code should work as it is now (see here: http://gw.minecraftforge.net/hr4y). It returns the bytes correctly (of the target class), or am I missing something?

Are you trying to re-write a method, or the whole class? I see a bit of both in there.

[sep87x]

I'm rewriting the decorate() method in the BiomeGenDesert class ... so a method.

[BlueSpud]

  On 7/18/2013 at 6:58 PM, sep87x said:

I'm rewriting the decorate() method in the BiomeGenDesert class ... so a method.

Try this, it replaces 2 method bodies, and I've used it to modify a few things. Just copy the method declaration and then write your own body in a new class.

public byte[] patch (String name, byte[] bytes, String desc, String iFile, String rname) throws IOException
{
	ClassNode cn = new ClassNode();
	ClassReader cr = new ClassReader(bytes);
	//the class node is now visiting the bytes that the class reader has
	cr.accept(cn,0);
	//giving us something we can look at all the methods
	Iterator<MethodNode> methods = cn.methods.iterator();
	//creating the method node we are going to mess with
	MethodNode mn = null;
	while (methods.hasNext())
	{
		MethodNode m = methods.next();
		if (m.name.equals(name) && m.desc.equals(desc))
		{
			System.out.printf("Found a method we want to transform%n");
			mn = m;
			break;
		}
	}
	//get the file we're going to replace a method with
	java.io.InputStream in = DHNTransformer.class.getResourceAsStream(iFile);
	byte[] newbyte = IOUtils.toByteArray(in);
	//get the method
	ClassNode cnr = new ClassNode();
	ClassReader crr = new ClassReader(newbyte);
	crr.accept(cnr,0);
	//find the right one
	Iterator<MethodNode> repalcemethods = cnr.methods.iterator();
	MethodNode mnr = null;
	while (repalcemethods.hasNext())
	{
		MethodNode m = repalcemethods.next();
		if (m.name.equals(rname))
		{
			System.out.printf("Found the right method that is going to be the replacement");
			mnr = m;
			break;
		}
	}
	//now we start changing the bodies
	mn.instructions = mnr.instructions;
	ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
	//let the writer visit the class now
	cn.accept(cw);

	return cw.toByteArray();

}

And how to use it:

if (arg0.equals("bhg")) {
		System.out.println("Doing RenderPlayer transformers in a obfuscated environment");
		newimport("",arg2);
		try {
			return patch("a", arg2, "(Lue;)V","/DHNCore/asm/Methods.class","renderFirstPersonArm");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
if (arg0.equals("net.minecraft.client.renderer.entity.RenderPlayer")) {
		System.out.println("Doing RenderPlayer transformers in a de-obfuscated environment");
		//make sure we import the class so that it does crash
		newimport("",arg2);
		try {
			return patch("renderFirstPersonArm", arg2, "(Lnet/minecraft/entity/player/EntityPlayer;)V","/DHNCore/asm/Methods.class","renderFirstPersonArm");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		}

[sep87x]

What about the newimport method?

[BlueSpud]

Its there. I forgot to mention that this won't let you use methods with 'this' ex: this.doSomething() I don't know if thats a problem for you.

[sep87x]

So, last question: the Methods.class in your patch method ... does it contain a method it should be replaced with?

 

P.S. While skimming the transformer class I found the error in the code ... well ... nobody was born perfect.