The current _zstd_set_c_parameters shares little between the two possible (int or dict) paths. By splitting the function, we can now use the Py_ssize_t AC converter.

One slight change worth noting is that the constructor won't raise an error when level is $-2^{63}$ but will just silently use the default. cc @erlend-aasland if there's a better method/sentinel we can use in the clinic to detect if the value has been set or not.

>>> _zstd.ZstdCompressor(level=-(1<<63)+1)
Traceback (most recent call last):
  File "<python-input-17>", line 1, in <module>
    _zstd.ZstdCompressor(level=-(1<<63)+1)
    ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
ValueError: compression level -9223372036854775807 not in valid range -131072 <= level <= 22.
>>> _zstd.ZstdCompressor(level=-(1<<63))
<compression.zstd.ZstdCompressor object at 0x7f61875b2210>

I also think it might be worth considering removing the level XOR options check, as we could adopt the rule that a compression level set in an options dict overrides the level parameter. I can see reasonable arguments to keep the status quo, however, so I've not done this yet.

A

cc @Rogdham

• Issue: Implement PEP 784 - Adding Zstandard to the Python standard library #132983