in uniffi_macros/src/object.rs [102:217]
fn interface_impl(object: &ObjectItem, options: &DeriveOptions) -> TokenStream {
let name = object.name();
let ident = object.ident();
let impl_spec = options.ffi_impl_header("FfiConverterArc", ident);
let lower_return_impl_spec = options.ffi_impl_header("LowerReturn", ident);
let lower_error_impl_spec = options.ffi_impl_header("LowerError", ident);
let type_id_impl_spec = options.ffi_impl_header("TypeId", ident);
let lift_ref_impl_spec = options.ffi_impl_header("LiftRef", ident);
let mod_path = match mod_path() {
Ok(p) => p,
Err(e) => return e.into_compile_error(),
};
let arc_self_type = quote! { ::std::sync::Arc<Self> };
let lower_arc = ffiops::lower(&arc_self_type);
let type_id_meta_arc = ffiops::type_id_meta(&arc_self_type);
let try_lift_arc = ffiops::try_lift(&arc_self_type);
let lower_return_type_arc = ffiops::lower_return_type(&arc_self_type);
let lower_return_arc = ffiops::lower_return(&arc_self_type);
let lower_error_arc = ffiops::lower_error(&arc_self_type);
let single_threaded_annotation = wasm_single_threaded_annotation();
quote! {
// All Object structs must be `Sync + Send`. The generated scaffolding will fail to compile
// if they are not, but unfortunately it fails with an unactionably obscure error message.
// By asserting the requirement explicitly, we help Rust produce a more scrutable error message
// and thus help the user debug why the requirement isn't being met.
#single_threaded_annotation
::uniffi::deps::static_assertions::assert_impl_all!(
#ident: ::core::marker::Sync, ::core::marker::Send
);
#[doc(hidden)]
#[automatically_derived]
/// Support for passing reference-counted shared objects via the FFI.
///
/// To avoid dealing with complex lifetime semantics over the FFI, any data passed
/// by reference must be encapsulated in an `Arc`, and must be safe to share
/// across threads.
unsafe #impl_spec {
// Don't use a pointer to <T> as that requires a `pub <T>`
type FfiType = *const ::std::os::raw::c_void;
/// When lowering, we have an owned `Arc` and we transfer that ownership
/// to the foreign-language code, "leaking" it out of Rust's ownership system
/// as a raw pointer. This works safely because we have unique ownership of `self`.
/// The foreign-language code is responsible for freeing this by calling the
/// `ffi_object_free` FFI function provided by the corresponding UniFFI type.
///
/// Safety: when freeing the resulting pointer, the foreign-language code must
/// call the destructor function specific to the type `T`. Calling the destructor
/// function for other types may lead to undefined behaviour.
fn lower(obj: ::std::sync::Arc<Self>) -> Self::FfiType {
let ptr = ::std::sync::Arc::into_raw(obj) as Self::FfiType;
::uniffi::deps::trace!("lower: {} ({:?})", #name, ptr);
ptr
}
/// When lifting, we receive an owned `Arc` that the foreign language code cloned.
fn try_lift(v: Self::FfiType) -> ::uniffi::Result<::std::sync::Arc<Self>> {
::uniffi::deps::trace!("lift: {} ({:?})", #name, v);
let v = v as *const #ident;
::std::result::Result::Ok(unsafe { ::std::sync::Arc::<Self>::from_raw(v) })
}
/// When writing as a field of a complex structure, make a clone and transfer ownership
/// of it to the foreign-language code by writing its pointer into the buffer.
/// The foreign-language code is responsible for freeing this by calling the
/// `ffi_object_free` FFI function provided by the corresponding UniFFI type.
///
/// Safety: when freeing the resulting pointer, the foreign-language code must
/// call the destructor function specific to the type `T`. Calling the destructor
/// function for other types may lead to undefined behaviour.
fn write(obj: ::std::sync::Arc<Self>, buf: &mut ::std::vec::Vec<u8>) {
::uniffi::deps::static_assertions::const_assert!(::std::mem::size_of::<*const ::std::ffi::c_void>() <= 8);
::uniffi::deps::bytes::BufMut::put_u64(buf, #lower_arc(obj) as ::std::primitive::u64);
}
/// When reading as a field of a complex structure, we receive a "borrow" of the `Arc`
/// that is owned by the foreign-language code, and make a clone for our own use.
///
/// Safety: the buffer must contain a pointer previously obtained by calling
/// the `lower()` or `write()` method of this impl.
fn try_read(buf: &mut &[u8]) -> ::uniffi::Result<::std::sync::Arc<Self>> {
::uniffi::deps::static_assertions::const_assert!(::std::mem::size_of::<*const ::std::ffi::c_void>() <= 8);
::uniffi::check_remaining(buf, 8)?;
#try_lift_arc(::uniffi::deps::bytes::Buf::get_u64(buf) as Self::FfiType)
}
const TYPE_ID_META: ::uniffi::MetadataBuffer = ::uniffi::MetadataBuffer::from_code(::uniffi::metadata::codes::TYPE_INTERFACE)
.concat_str(#mod_path)
.concat_str(#name);
}
unsafe #lower_return_impl_spec {
type ReturnType = #lower_return_type_arc;
fn lower_return(obj: Self) -> ::std::result::Result<Self::ReturnType, ::uniffi::RustCallError> {
#lower_return_arc(::std::sync::Arc::new(obj))
}
}
unsafe #lower_error_impl_spec {
fn lower_error(obj: Self) -> ::uniffi::RustBuffer {
#lower_error_arc(::std::sync::Arc::new(obj))
}
}
unsafe #lift_ref_impl_spec {
type LiftType = ::std::sync::Arc<Self>;
}
#type_id_impl_spec {
const TYPE_ID_META: ::uniffi::MetadataBuffer = #type_id_meta_arc;
}
}
}