Slices

Static Slices

(Supported by c, cpp, kotlin, and nanobind, queried with #[diplomat::cfg(supports=static_slices)])

Support for &'static slices.

Primitive Structs

(Supported by c, cpp, and nanobind, queried with #[diplomat::cfg(supports=abi_compatibles)])

Some Diplomat backends support providing slices of structs as function parameters:

#[diplomat::bridge]
mod ffi {
    #[diplomat::attr(auto, abi_compatible)]
    struct Struct {
        a : bool,
        b : i32
    }

    impl Struct {
        pub fn bar(slice : &mut [Struct]) {}
        pub fn baz(other_slice : &[Struct]) {}
    }
}

Mapping Diplomat types from the bound language to the C API can vary based on what types are in the struct. To reduce this complexity, slices of structs come with some restrictions:

• The struct type must have #[diplomat::attr(auto, abi_compatible)] attribute.
• The struct can only have fields that are either:
  • Primitive
  • Nested primitive structs

Opaques

(Supported by queried with #[diplomat::cfg(supports=opaque_slices)])

Currently, opaque slices are restricted to input only, with no borrows allowed in the output (See the relevant issue on GitHub):

// Allowed:
pub fn takes_opaque_slice<'a>(&'a self, sl: &'a [MyOpaque]);

// Will throw an error on lowering:
pub fn borrows_slice_opaque<'a>(sl : &'a [MyOpaque]) -> &'a SomeType;