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twoolie / NBT

Python Parser/Writer for the NBT file format, and it's container the RegionFile.
MIT License
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Error while creating data: "struct.error: int too large to convert" #161

Open alex4200 opened 2 years ago

alex4200 commented 2 years ago

Using NBT 1.5.1 on MacOS 12.2.1 I have problems with creating NBT data. The main code is as follows:

    chunk_data = BytesIO()
    nbt_data = self.get_nbt()
    nbt_data.write_file(buffer=chunk_data)  # ERROR LINE

where I get the following error:

  File "/Users/a/Private/Minecraft/PyBlock/PyBlock/pyblock/chunk.py", line 248, in get_bytes
    nbt_data.write_file(buffer=chunk_data)
  File "/Users/a/Private/Minecraft/PyBlock/venv/lib/python3.8/site-packages/nbt/nbt.py", line 712, in write_file
    self._render_buffer(self.file)
  File "/Users/a/Private/Minecraft/PyBlock/venv/lib/python3.8/site-packages/nbt/nbt.py", line 515, in _render_buffer
    tag._render_buffer(buffer)
  File "/Users/a/Private/Minecraft/PyBlock/venv/lib/python3.8/site-packages/nbt/nbt.py", line 427, in _render_buffer
    tag._render_buffer(buffer)
  File "/Users/a/Private/Minecraft/PyBlock/venv/lib/python3.8/site-packages/nbt/nbt.py", line 515, in _render_buffer
    tag._render_buffer(buffer)
  File "/Users/a/Private/Minecraft/PyBlock/venv/lib/python3.8/site-packages/nbt/nbt.py", line 515, in _render_buffer
    tag._render_buffer(buffer)
  File "/Users/a/Private/Minecraft/PyBlock/venv/lib/python3.8/site-packages/nbt/nbt.py", line 317, in _render_buffer
    buffer.write(self.fmt.pack(*self.value))
struct.error: int too large to convert

The interesting thing is: Sometimes there is no problem! I run the EXACT same code, and I DO NOT GET ANY ERROR. In most cases I do get this error above. But in some cases, all is working fine.

Maybe that is something known? I will try to """reproduce""" this error. Not sure if that is possible at all.

I tried to create a "reproducible" example by writing the nbt data to a file. But either I get the exact same error when doing

nbt_data.write_file("test.nbt")

or it works, and I can use the correct content of test.nbt. Which does not help debug anything...

When I print out the value of self.value in the line I get the error, the values are always different. It is random!

unycorn commented 2 years ago

I just figured out why I was getting this problem and here it goes: Although the chunk data is stored in what looks simply like 64 bit integers, it is actually a SIGNED long. This means you need the leftmost bit to represent a minus sign when dealing with it in python. I wrote an awful piece of code to convert the "too big" unsigned data element to a signed one that can be passed

data = int.from_bytes((data).to_bytes(8, 'big', signed=False), 'big', signed=True)

I guess it's been a few months but if you see this hello!