    extern "Rust" {
        #[swift_bridge(swift_name = "{{ reg_camel }}ViaCallback")]
        fn {{ service_snake }}_{{ reg_snake }}_via_callback(
            self: &mut {{ service_name }},
{%- for meta_param in metadata_params %}
            {{ meta_param.name }}: {{ meta_param.rust_type }},
{%- endfor %}
            ctx: *mut std::ffi::c_void,
            callback: extern "C" fn(*mut std::ffi::c_void, *const u8, usize) -> *mut u8,
        ) -> i32;
    }
