[1.7.10] bytecode doesn't seem to match sourcecode

[kauan99]

I'm trying to experiement with ASM, but I'm facing a weird problem.

 

I'm looking into what was supposed to be the bytecode of EntityPlayer.setCurrentItemOrArmor(int, ItemStack). I'm really bad at reading bytecode, but this doesn't seem right even to me:

 

java source:

 

    public void setCurrentItemOrArmor(int p_70062_1_, ItemStack p_70062_2_)
    {
        if (p_70062_1_ == 0)
        {
            this.inventory.mainInventory[this.inventory.currentItem] = p_70062_2_;
        }
        else
        {
            this.inventory.armorInventory[p_70062_1_ - 1] = p_70062_2_;
        }
    }

 

bytecode:

aload_0
getfield yz/bm Lyx;
getfield yx/b [Ladd;
iload_1
aload_2
aastore
return

 

let me see if I inderstand this correctly:

 

• aload_0

  puts a pointer to

  this

  on the stack
  

• getfield yz/bm Lyx;

  gets the field from the pointer on top of the stack (

  this

  ) identified as

  bm

  in the constants pool (

  inventory

  ), which is of type

  Lyx

  (

  pointer to InventoryPlayer

  ), pops the pointer on top the stack and puts the pointer to the field we just got onto the stack
  

• getfield yx/b [Ladd;

  same operation above, now resulting in we having a pointer to

  this.inventory.armorInventory

  (type:

  array of pointers to ItemStack

  ) on the stack
  

• iload_1

  stacks the

  int

  value param 1 on top of the stack
  

• aload_2

  stacks the

  ItemStack

  pointer param 2 on top of the stack
  

• aastore probably reads the pointer on top of the stack to some register

  A

  and pops it from the stack, then reads an

  int

  from the stack to some register

  B

  and pops it too, then stores the pointer at register

  A

  at the address obtained by performing pointer arithmetic on the pointer now on top of the stack (to

  this.inventory.armorInventory

  ), and finally pops this last pointer out of the stack
  

• return

  we all know that one
  

 

where is the code that checks if the index is 0? if this method was used it would put a sword at your helmet slot. where is the subtraction param1 - 1?

[kauan99]

how do I get the bytecode for that method? I checked the joined.srg file to find the method and the class, and picked the class from my .minecraft\versions\1.7.10.jar file (yz.class, method c(ILadd;)V). am I supposed to get the class file from somewhere else?

 

also, if someone would be so kind to check my interpretation of the bytecode for correctness that would be really apreciated.

[shadowfacts]

There is a very handy plugin for IntelliJ IDEA called ASM Bytecode Outline which allows you to view the ASM and bytecode versions of classes inside IDEA.

[kauan99]

There is a very handy plugin for IntelliJ IDEA called ASM Bytecode Outline which allows you to view the ASM and bytecode versions of classes inside IDEA.

 

yeah, thanks! I'm aware of that and I use eclipse and I can't install it for my life.... eclipse always displays and error.

[kauan99]

please I'd really like to know how to see the bytecode for minecraft classes. maybe the source displays the class after forge patches it. I want to see the source of the class after all patching has been done. could anybody help me with that? thanks.

[kauan99]

I used bytecode viewer, the problem is I don't know where to find the .class files. they're not inside .minecraft\versions\1.7.10.jar because that's where I got that .class file from. it seems only vanilla classes are in there? maybe forge uses ASM to transform the classes into what we see in the source code? All I want is access to the .class files the way they actually are when we play modded minecraft. I want to know where they are, that's all.

[kauan99]

I can't locate those files on disk.

[Draco18s]

See my post here. You should be able to follow the folder path and find the original jar files nearby.

 

http://www.minecraftforge.net/forum/index.php/topic,33642.0.html

[kauan99]

thanks!