WIP: Rust wrapper

[nyurik]

TODO/Goals

• Include core header files
• Generate/write a tiny C++ wrapper that Rust can communicate with
• Compile core with cmake, possibly including the tiny C++ generated code - resulting in a statically-linkable (from Rust) lib
• Use proper Rust strings instead of &CStr and CString where it is not performance critical.
  • PROs: consistency with the Rust ecosystem, proper utf-8 validated strings going in and out of the crate.
  • CONs: requires extra allocation and validation. On invalid string will panic, or we must introduce Result<String> for proper error reporting.

Implementation ideas

Current thinking is to get cmake to produce a static library. All steps must be initiated by the platform/rust-cxx/build.rs:

• cxx bridge generates a header file out of the #[cxx::bridge] mod ffi { ... } in platform/rust-cxx/src/main.rs
• cmake crate executes cmake with special flags to pick up that header file, plus any other CC and H files in the rust-cxx dirs, plus the rest of the core and produces static lib
• main.rs links to it and calls get_version or some other basic thing

[github-actions]

Bloaty Results 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  [ = ]       0  [ = ]       0    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-3181-compared-to-main.txt

Compared to d387090 (legacy)

    FILE SIZE        VM SIZE    
 --------------  -------------- 
   +31% +36.1Mi  +438% +26.2Mi    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-3181-compared-to-legacy.txt

[github-actions]

Benchmark Results ⚡

Benchmark                                                     Time             CPU      Time Old      Time New       CPU Old       CPU New
------------------------------------------------------------------------------------------------------------------------------------------
OVERALL_GEOMEAN                                            -0.0071         -0.0074             0             0             0             0

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/benchmark-results/pr-3181-compared-to-main.txt

[louwers]

These are pending deprecation and removal.

[nyurik]

For now these are good for testing, but I agree that we should remove these

[github-actions]

Bloaty Results (iOS) 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  [ = ]       0  [ = ]       0    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results-ios/pr-3181-compared-to-main.txt