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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
use crate::{
export::ImplItem,
ffiops,
fnsig::{FnKind, FnSignature, ReceiverArg},
util::{
create_metadata_items, derive_ffi_traits, ident_to_string, mod_path, tagged_impl_header,
},
};
use proc_macro2::{Span, TokenStream};
use quote::{format_ident, quote};
use std::iter;
use syn::Ident;
/// Generate a trait impl that calls foreign callbacks
///
/// This generates:
/// * A `repr(C)` VTable struct where each field is the FFI function for the trait method.
/// * A FFI function for foreign code to set their VTable for the interface
/// * An implementation of the trait using that VTable
pub(super) fn trait_impl(
mod_path: &str,
trait_ident: &Ident,
items: &[ImplItem],
) -> syn::Result<TokenStream> {
let trait_name = ident_to_string(trait_ident);
let trait_impl_ident = trait_impl_ident(&trait_name);
let vtable_type = format_ident!("UniFfiTraitVtable{trait_name}");
let vtable_cell = format_ident!("UNIFFI_TRAIT_CELL_{}", trait_name.to_uppercase());
let init_ident = Ident::new(
&uniffi_meta::init_callback_vtable_fn_symbol_name(mod_path, &trait_name),
Span::call_site(),
);
let methods = items
.iter()
.map(|item| match item {
ImplItem::Constructor(sig) => Err(syn::Error::new(
sig.span,
"Constructors not allowed in trait interfaces",
)),
ImplItem::Method(sig) => Ok(sig),
})
.collect::<syn::Result<Vec<_>>>()?;
let vtable_fields = methods.iter().map(|sig| {
let ident = &sig.ident;
let param_names = sig.scaffolding_param_names();
let param_types = sig.scaffolding_param_types();
let lift_return_type = ffiops::lift_return_type(&sig.return_ty);
if !sig.is_async {
quote! {
#ident: extern "C" fn(
uniffi_handle: u64,
#(#param_names: #param_types,)*
uniffi_out_return: &mut #lift_return_type,
uniffi_out_call_status: &mut ::uniffi::RustCallStatus,
),
}
} else {
quote! {
#ident: extern "C" fn(
uniffi_handle: u64,
#(#param_names: #param_types,)*
uniffi_future_callback: ::uniffi::ForeignFutureCallback<#lift_return_type>,
uniffi_callback_data: u64,
uniffi_out_return: &mut ::uniffi::ForeignFuture,
),
}
}
});
let trait_impl_methods = methods
.iter()
.map(|sig| gen_method_impl(sig, &vtable_cell))
.collect::<syn::Result<Vec<_>>>()?;
let has_async_method = methods.iter().any(|m| m.is_async);
let impl_attributes = has_async_method.then(|| quote! { #[::async_trait::async_trait] });
Ok(quote! {
struct #vtable_type {
#(#vtable_fields)*
uniffi_free: extern "C" fn(handle: u64),
}
static #vtable_cell: ::uniffi::UniffiForeignPointerCell::<#vtable_type> = ::uniffi::UniffiForeignPointerCell::<#vtable_type>::new();
#[no_mangle]
extern "C" fn #init_ident(vtable: ::std::ptr::NonNull<#vtable_type>) {
#vtable_cell.set(vtable);
}
#[derive(Debug)]
struct #trait_impl_ident {
handle: u64,
}
impl #trait_impl_ident {
fn new(handle: u64) -> Self {
Self { handle }
}
}
::uniffi::deps::static_assertions::assert_impl_all!(#trait_impl_ident: ::core::marker::Send);
#impl_attributes
impl #trait_ident for #trait_impl_ident {
#(#trait_impl_methods)*
}
impl ::std::ops::Drop for #trait_impl_ident {
fn drop(&mut self) {
let vtable = #vtable_cell.get();
(vtable.uniffi_free)(self.handle);
}
}
})
}
pub fn trait_impl_ident(trait_name: &str) -> Ident {
Ident::new(
&format!("UniFFICallbackHandler{trait_name}"),
Span::call_site(),
)
}
pub fn ffi_converter_callback_interface_impl(
trait_ident: &Ident,
trait_impl_ident: &Ident,
udl_mode: bool,
) -> TokenStream {
let trait_name = ident_to_string(trait_ident);
let dyn_trait = quote! { dyn #trait_ident };
let box_dyn_trait = quote! { ::std::boxed::Box<#dyn_trait> };
let lift_impl_spec = tagged_impl_header("Lift", &box_dyn_trait, udl_mode);
let type_id_impl_spec = tagged_impl_header("TypeId", &box_dyn_trait, udl_mode);
let derive_ffi_traits = derive_ffi_traits(&box_dyn_trait, udl_mode, &["LiftRef", "LiftReturn"]);
let mod_path = match mod_path() {
Ok(p) => p,
Err(e) => return e.into_compile_error(),
};
let try_lift_self = ffiops::try_lift(quote! { Self });
quote! {
#[doc(hidden)]
#[automatically_derived]
unsafe #lift_impl_spec {
type FfiType = u64;
fn try_lift(v: Self::FfiType) -> ::uniffi::deps::anyhow::Result<Self> {
::std::result::Result::Ok(::std::boxed::Box::new(<#trait_impl_ident>::new(v)))
}
fn try_read(buf: &mut &[u8]) -> ::uniffi::deps::anyhow::Result<Self> {
use ::uniffi::deps::bytes::Buf;
::uniffi::check_remaining(buf, 8)?;
#try_lift_self(buf.get_u64())
}
}
#[doc(hidden)]
#[automatically_derived]
#type_id_impl_spec {
const TYPE_ID_META: ::uniffi::MetadataBuffer = ::uniffi::MetadataBuffer::from_code(
::uniffi::metadata::codes::TYPE_CALLBACK_INTERFACE,
)
.concat_str(#mod_path)
.concat_str(#trait_name);
}
#derive_ffi_traits
}
}
/// Generate a single method for [trait_impl]. This implements a trait method by invoking a
/// foreign-supplied callback.
fn gen_method_impl(sig: &FnSignature, vtable_cell: &Ident) -> syn::Result<TokenStream> {
let FnSignature {
ident,
is_async,
return_ty,
kind,
receiver,
name,
span,
..
} = sig;
if !matches!(kind, FnKind::TraitMethod { .. }) {
return Err(syn::Error::new(
*span,
format!(
"Internal UniFFI error: Unexpected function kind for callback interface {name}: {kind:?}",
),
));
}
let self_param = match receiver {
Some(ReceiverArg::Ref) => quote! { &self },
Some(ReceiverArg::Arc) => quote! { self: Arc<Self> },
None => {
return Err(syn::Error::new(
*span,
"callback interface methods must take &self as their first argument",
));
}
};
let params = sig.params();
let lower_exprs = sig.args.iter().map(|a| {
let lower = ffiops::lower(&a.ty);
let ident = &a.ident;
quote! { #lower(#ident) }
});
let lift_return_type = ffiops::lift_return_type(&sig.return_ty);
let lift_foreign_return = ffiops::lift_foreign_return(&sig.return_ty);
if !is_async {
Ok(quote! {
fn #ident(#self_param, #(#params),*) -> #return_ty {
let vtable = #vtable_cell.get();
let mut uniffi_call_status: ::uniffi::RustCallStatus = ::std::default::Default::default();
let mut uniffi_return_value: #lift_return_type = ::uniffi::FfiDefault::ffi_default();
(vtable.#ident)(self.handle, #(#lower_exprs,)* &mut uniffi_return_value, &mut uniffi_call_status);
#lift_foreign_return(uniffi_return_value, uniffi_call_status)
}
})
} else {
Ok(quote! {
async fn #ident(#self_param, #(#params),*) -> #return_ty {
let vtable = #vtable_cell.get();
::uniffi::foreign_async_call::<_, #return_ty, crate::UniFfiTag>(move |uniffi_future_callback, uniffi_future_callback_data| {
let mut uniffi_foreign_future: ::uniffi::ForeignFuture = ::uniffi::FfiDefault::ffi_default();
(vtable.#ident)(self.handle, #(#lower_exprs,)* uniffi_future_callback, uniffi_future_callback_data, &mut uniffi_foreign_future);
uniffi_foreign_future
}).await
}
})
}
}
pub(super) fn metadata_items(
self_ident: &Ident,
items: &[ImplItem],
module_path: &str,
docstring: String,
) -> syn::Result<Vec<TokenStream>> {
let trait_name = ident_to_string(self_ident);
let callback_interface_items = create_metadata_items(
"callback_interface",
&trait_name,
quote! {
::uniffi::MetadataBuffer::from_code(::uniffi::metadata::codes::CALLBACK_INTERFACE)
.concat_str(#module_path)
.concat_str(#trait_name)
.concat_long_str(#docstring)
},
None,
);
iter::once(Ok(callback_interface_items))
.chain(items.iter().map(|item| match item {
ImplItem::Method(sig) => sig.metadata_items(),
_ => unreachable!("traits have no constructors"),
}))
.collect()
}