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use proc_macro2::{Ident, Span, TokenStream};
use quote::quote;
use syn::DeriveInput;
use crate::{
ffiops,
util::{
create_metadata_items, either_attribute_arg, extract_docstring, ident_to_string, kw,
mod_path, wasm_single_threaded_annotation, AttributeSliceExt, UniffiAttributeArgs,
},
DeriveOptions,
};
use syn::{parse::ParseStream, LitStr, Token};
use uniffi_meta::ObjectImpl;
/// Handle #[uniffi(...)] attributes for objects
#[derive(Clone, Default)]
pub struct ObjectAttr {
pub name: Option<String>,
}
impl UniffiAttributeArgs for ObjectAttr {
fn parse_one(input: ParseStream<'_>) -> syn::Result<Self> {
let lookahead = input.lookahead1();
if lookahead.peek(kw::name) {
let _: kw::name = input.parse()?;
let _: Token![=] = input.parse()?;
let name = Some(input.parse::<LitStr>()?.value());
Ok(Self { name })
} else {
Err(syn::Error::new(
input.span(),
format!("attribute `{input}` is not supported here."),
))
}
}
fn merge(self, other: Self) -> syn::Result<Self> {
Ok(Self {
name: either_attribute_arg(self.name, other.name)?,
})
}
}
/// Stores parsed data from the Derive Input for the struct/enum.
struct ObjectItem {
ident: Ident,
docstring: String,
attr: ObjectAttr,
}
impl ObjectItem {
fn new(input: DeriveInput) -> syn::Result<Self> {
let attr = input.attrs.parse_uniffi_attr_args::<ObjectAttr>()?;
Ok(Self {
ident: input.ident,
docstring: extract_docstring(&input.attrs)?,
attr,
})
}
fn ident(&self) -> &Ident {
&self.ident
}
fn name(&self) -> String {
ident_to_string(&self.ident)
}
fn foreign_name(&self) -> String {
match &self.attr.name {
Some(name) => name.clone(),
None => self.name(),
}
}
fn docstring(&self) -> &str {
self.docstring.as_str()
}
}
pub fn expand_object(input: DeriveInput, options: DeriveOptions) -> syn::Result<TokenStream> {
let module_path = mod_path()?;
let object = ObjectItem::new(input)?;
let name = &object.foreign_name();
let ident = object.ident();
let clone_fn_ident = Ident::new(
&uniffi_meta::clone_fn_symbol_name(&module_path, name),
Span::call_site(),
);
let free_fn_ident = Ident::new(
&uniffi_meta::free_fn_symbol_name(&module_path, name),
Span::call_site(),
);
let meta_static_var = options.generate_metadata.then(|| {
interface_meta_static_var(name, ObjectImpl::Struct, object.docstring())
.unwrap_or_else(syn::Error::into_compile_error)
});
let interface_impl = interface_impl(&object, &options);
Ok(quote! {
#[doc(hidden)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn #clone_fn_ident(
handle: ::uniffi::ffi::Handle,
call_status: &mut ::uniffi::RustCallStatus
) -> ::uniffi::ffi::Handle {
::uniffi::deps::trace!("clone: {} ({:?})", #name, handle);
::uniffi::rust_call(call_status, || {
unsafe {
handle.clone_arc_handle::<#ident>()
};
::std::result::Result::Ok(handle)
})
}
#[doc(hidden)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn #free_fn_ident(
handle: ::uniffi::ffi::Handle,
call_status: &mut ::uniffi::RustCallStatus
) {
::uniffi::deps::trace!("free: {} ({:?})", #name, handle);
::uniffi::rust_call(call_status, || {
::std::mem::drop(unsafe {
handle.into_arc::<#ident>()
});
::std::result::Result::Ok(())
});
}
#interface_impl
#meta_static_var
})
}
fn interface_impl(object: &ObjectItem, options: &DeriveOptions) -> TokenStream {
let name = object.foreign_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 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
);
// We're going to be casting raw pointers to `u64` values to pass them across the FFI.
// Ensure that we're not on some 128-bit machine where this would overflow.
::uniffi::deps::static_assertions::const_assert!(::std::mem::size_of::<*const ()>() <= 8);
#[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 {
type FfiType = ::uniffi::ffi::Handle;
/// 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 {
::uniffi::deps::trace!("lower: {} {:?}", #name, ::std::sync::Arc::as_ptr(&obj));
let handle = ::uniffi::ffi::Handle::from_arc(obj);
handle
}
/// When lifting, we receive an owned `Arc` that the foreign language code cloned.
fn try_lift(handle: Self::FfiType) -> ::uniffi::Result<::std::sync::Arc<Self>> {
::uniffi::deps::trace!("lift: {} ({:?})", #name, handle);
::std::result::Result::Ok(unsafe { handle.into_arc() })
}
/// 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::bytes::BufMut::put_u64(buf, #lower_arc(obj).as_raw());
}
/// 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::check_remaining(buf, 8)?;
#try_lift_arc(::uniffi::ffi::Handle::from_raw_unchecked(::uniffi::deps::bytes::Buf::get_u64(buf)))
}
const TYPE_ID_META: ::uniffi::MetadataBuffer = ::uniffi::MetadataBuffer::from_code(::uniffi::metadata::codes::TYPE_INTERFACE)
.concat_str(module_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;
}
}
}
pub(crate) fn interface_meta_static_var(
name: &str,
imp: ObjectImpl,
docstring: &str,
) -> syn::Result<TokenStream> {
let code = match imp {
ObjectImpl::Struct => quote! { ::uniffi::metadata::codes::INTERFACE },
ObjectImpl::Trait => quote! { ::uniffi::metadata::codes::TRAIT_INTERFACE },
ObjectImpl::CallbackTrait => quote! { ::uniffi::metadata::codes::CALLBACK_TRAIT_INTERFACE },
};
Ok(create_metadata_items(
"interface",
name,
quote! {
::uniffi::MetadataBuffer::from_code(#code)
.concat_str(module_path!())
.concat_str(#name)
.concat_long_str(#docstring)
},
None,
))
}