rust-integration.md

Lambdaworks wrapper

For now, this is a mock containing only a "number" function that always return 42. It's a proof of concept of a go package that integrates with a rust library.

Package structure

These are the relevant files:

./pkg/lambdaworks: go package wrapper so that other packages can call this
        │          one without worrying about FFI, C or rust.
        ├──lambdaworks.go: go wrapper library code. Casts C types to go types.
        └── lib: directory with the rust and C code.
            ├── lambdaworks.h: C headers representing the functions that will
            │                  be exported to go.
            └── lambdaworks: Rust package.
                ├── Cargo.Toml: Rust package definition.
                └── src/lib.rs: rust library.

Compiling

The rust package can be compiled by moving to the lib/lambdaworks directory and executing cargo build --release. This produces a lib/lambdaworks/target/liblambdaworks.a file that will be imported by the lambdaworks.go as a static library, as we can see in the comment over the Number function.

In Makefile we can see that one of the steps is actually moving to the rust project, compiling, and then copying the archive file to the lib directory so it can be consumed by the go code.

Next steps:

The lambdaworks math and crypto rust dependencies are already included in the Cargo.toml, but they are not used. The first step would be to add a wrapper that manipulates the finite field type instead of a simple integer.