🔒 Getting inconsisten results for uncompressing certain deflate compressed bytestreams between C/Nim

[hot harbor]

python code: https://www.online-python.com/O5FjtZKr4c Nim code: https://play.nim-lang.org/#pasty=OKkTiTma
Tested wth zlib in C as well and get the same result as in Nim, data does not uncompress.
Would really like to know what does python do differently that this data can be uncompressed in it.

[warm frost]

@hot harbor

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[hot harbor]

Getting inconsisten results for uncompressing certain deflate compressed bytestreams between C/py

[mental obsidian]

Interesting. I think that question would be more suited to #internals-and-peps as you want to actually know something about internals and there might be people who know where to look. While the #1035199133436354600 is usually used for simpler stuff and people knowing internals probably don't check it

When I tried to prepend the gzip header and use gzip command, I got unexpected end of file, so that might be what python swallows but everyone more string errors on?

Python's zlib module is implemented in C here https://github.com/python/cpython/blob/3.12/Modules/zlibmodule.c

And here it seems we have the method used to decompress https://github.com/python/cpython/blob/0181aa2e3efedc6504b27f6fe74f096e5e454286/Modules/zlibmodule.c#L848

[warm frost]

Modules/zlibmodule.c line 848

zlib.Decompress.decompress```

[mental obsidian]

Huh... If I understand the code correctly (without going into the other functions), it seems it finds the eof and then marks it (lines 938-941) but doesn't actually error or abort (like with buffer error just after) - and therefore goes to check in line 952 which decides that there's some data, so it's a success...

[warm frost]

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