It's about as good as it can get for this kind of code.
[1] https://www.reddit.com/r/rust/comments/1ixt1ei/zlibrs_is_fas...
This is explicitly an AI-coded project, Antirez argues that LLMs are worse at writing Rust than C because so much high quality systems code (think e.g. sendmail) that ends up in AI training sets is C, not Rust. Another related argument is that the more detailed syntax and compiler feedback found in Rust compared to C are really a negative for LLM workflows.
There's plenty of room to disagree wrt. this of course: without the strong typing checks of Rust around e.g. indirect references, safety and correctness ends up being a global property in typical C programs, and LLMs are terrible wrt. reasoning about global properties. You're better off forcing them to adapt to a different local syntax that does a more complete job of enforcing modularity, since this is comparatively foolproof.
Much easier to work with a language you are most comfortable with right?