cargo-c VS cbindgen

I'm writing this to explain some of the problems cargo-c solves and hopefully give few pointers since the README containing all the documentation maybe grew to be fairly big.

Beside rav1e there is need also for cargo-c, so that rav1e can provide C-compatible library.

Rust is just another programming language that’s quite similar to C++. The main difference is there’s like 4 types for String (some are references and some are owned) and methods for a struct go in a `impl StructName` block after the struct definition instead of inside it.

I don’t really know rust either but I’m currently writing some bindings to expose Rust libraries to NodeJS and not having too much trouble.

For rust -> c++ I googled one time and found this tool which Mozilla seems to use to call Rust from C++ in their web browser, maybe it would “just work”: https://github.com/mozilla/cbindgen?tab=readme-ov-file

To not generate the header using cbindgen, it will copy the header {crate name}.h from the assets/ directory.

Golang uses cgo to communicate with external C libraries and Rust uses FFI (Foreign function interfaces) to export C functions. Additionally, a library for automatically generating bindings can be used to generate the header files (.h). In our case, we'll only be exporting two C functions, so using cbindgen is overkill but we'll use it regardless because why not?  Firstly, we'll write the rust functions we want to export. We'll start by creating a new rust library:

[1]: https://github.com/mozilla/cbindgen

As a 2-step approach, you could also probably use https://github.com/mozilla/cbindgen and then Nim's native C FFI.

The tooling for the first kind -- calling Rust from another language -- is a bit less developed, and tends to rely on code generation that doesn't necessarily produce a natural C API. cbindgen, uniffi, cxx, and Diplomat all take this course.

There's also cbindgen for automating the generation of C headers once you've got your code in the right shape and you'll also want to read the Rustonomicon.

You can backport Rust standard library to C using https://github.com/eqrion/cbindgen .

Later we'll see what cbindgen essentially does is receive a configuration and a Rust library and then spit out a C header (.h) file. One might think that what cbindgen is doing might not be that special and can be done by hand. In which some cases that might be true if the project is simple enough. Though additionally as the cbindgen documentation states:

Fuck it, I'll take the bait. Rust allows for amazing C interop by allowing for exporting of C types as a dynamic library, like C. Unlike C, this still allows for Rust's advanced checking at compile time. librsvg is one such library that is being used in the GTK ecosystem that is also almost completely Rust. You can use tools like cbindgen to generate C bindings.