fix: correct edge values of window_bits

[f3fora]

see https://docs.python.org/3/library/zlib.html

[mkitti]

I'm not clear if this agrees with https://www.zlib.net/manual.html

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.66%. Comparing base (3192d0f) to head (e6fdac9).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #60   +/-   ##
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  Coverage   91.66%   91.66%           
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  Files           4        4           
  Lines         156      156           
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  Hits          143      143           
  Misses         13       13           

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[nhz2]

The zlib manual section on deflateInit2 is not straight forward about windowbits=8

The windowBits parameter is the base two logarithm of the window size (the size of the history buffer). It should be in the range 8..15 for this version of the library. Larger values of this parameter result in better compression at the expense of memory usage. The default value is 15 if deflateInit is used instead.

For the current implementation of deflate(), a windowBits value of 8 (a window size of 256 bytes) is not supported. As a result, a request for 8 will result in 9 (a 512-byte window). In that case, providing 8 to inflateInit2() will result in an error when the zlib header with 9 is checked against the initialization of inflate(). The remedy is to not use 8 with deflateInit2() with this initialization, or at least in that case use 9 with inflateInit2().

I think windowbits=8 was originally intended to work, but there is a bug in zlib so now it isn't allowed.

Ref: madler/zlib#737 madler/zlib#171

[nhz2]

I'm going to merge this now to be able to move forward on some other issues, but @mkitti and @f3fora please open an issue if there are any problems with this change, or if you need support for other advanced zlib configuration options.