Fix inflate() flush modes and implement state.data_type

[cjgriscom]

This PR address the following issues:

• state.data_type is always 0
• flush is not respected in inflate() #114
• Add logic to advance from TYPE state to TYPE_DO state

[folkertdev]

nice work!

it's interesting that none of the zlib/zlib-ng tests catch these bugs. We'd like to add additional tests when we find that incorrect behavior slipped through.

[folkertdev]

because we're only ever in one mode, I think a match is nicer here. Also can tests be added that verify the behavior (probably from the libz-rs-sys` crate's test modules) versus zlib itself?

[cjgriscom]

Hmm, you're right. I will double-check zlib's original logic and correct it to one match. I will also put some tests together that demonstrate parity b/t libz-rs-sys and libz-sys

[cjgriscom]

I split the changes into 3 commits and added a test which compares the stream positions and state data after each call to inflate(). It demonstrates that all three changes are needed for consistency

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.59%. Comparing base (52e1628) to head (d282f90).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #113      +/-   ##
==========================================
+ Coverage   89.95%   90.59%   +0.63%     
==========================================
  Files          36       36              
  Lines        9664     9767     +103     
==========================================
+ Hits         8693     8848     +155     
+ Misses        971      919      -52     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[folkertdev]

After your changes, other tests were failing. Turns out this is what the LEN_ state is for. It looks really weird otherwise because it does no real work, just falls throught, but apparently that state is important for the correct behavior of Flush::Trees.

Also for the future, our CI checks formatting and runs cargo clippy (also on tests). We advise you run those tools locally at every commit, that'll save a bunch of back-and-forth with CI.

[folkertdev]

Thanks for these fixes!

[cjgriscom]

Thanks for merging and for your work on this crate!