[feature] #4060: add support for boxed slices in FFI (#4062)

Signed-off-by: Marin Veršić <marin.versic101@gmail.com>

Cargo.toml

@@ -135,12 +135,13 @@ parity-scale-codec = { version = "3.6.5", default-features = false }
 json5 = "0.4.1"
 
 [workspace.lints]
+rustdoc.private_doc_tests = "deny"
+
 rust.anonymous_parameters = "deny"
 rust.future_incompatible = "deny"
 rust.missing_copy_implementations = "deny"
 rust.missing_docs = "deny"
 rust.nonstandard_style = "deny"
-rust.private_doc_tests = "deny"
 rust.rust_2018_idioms = "deny"
 rust.trivial_casts = "deny"
 rust.trivial_numeric_casts = "deny"

ffi/derive/src/convert.rs

@@ -254,7 +254,6 @@ pub fn derive_ffi_type(emitter: &mut Emitter, input: &syn2::DeriveInput) -> Toke
     };
 
     let name = &input.ident;
-
     if let darling::ast::Data::Enum(variants) = &input.data {
         if variants.is_empty() {
             emit!(

ffi/derive/src/wrapper.rs

@@ -382,6 +382,7 @@ fn gen_impl_ffi(name: &Ident, generics: &syn2::Generics) -> TokenStream {
             type Ref<#lifetime> = &#lifetime iroha_ffi::Extern where #(#lifetime_bounded_where_clause),*;
             type RefMut<#lifetime> = &#lifetime mut iroha_ffi::Extern where #(#lifetime_bounded_where_clause),*;
             type Box = Box<iroha_ffi::Extern>;
+            type SliceBox = Box<[iroha_ffi::Extern]>;
             type SliceRef<#lifetime> = &#lifetime [iroha_ffi::ir::Transparent] where #(#lifetime_bounded_where_clause),*;
             type SliceRefMut<#lifetime> = &#lifetime mut [iroha_ffi::ir::Transparent] where #(#lifetime_bounded_where_clause),*;
             type Vec = Vec<iroha_ffi::ir::Transparent>;

ffi/src/ir.rs

@@ -105,6 +105,8 @@ pub trait IrTypeFamily {
         Self: 'itm;
     /// [`Ir`] type that [`Box<T>`] is mapped into
     type Box;
+    /// [`Ir`] type that `Box<[T]>` is mapped into
+    type SliceBox;
     /// [`Ir`] type that `&[T]` is mapped into
     type SliceRef<'itm>
     where
@@ -124,6 +126,7 @@ impl<R: Cloned> IrTypeFamily for R {
     // NOTE: Unused
     type RefMut<'itm> = () where Self: 'itm;
     type Box = Box<Self>;
+    type SliceBox = Box<[Self]>;
     type SliceRef<'itm> = &'itm [Self] where Self: 'itm;
     // NOTE: Unused
     type SliceRefMut<'itm> = () where Self: 'itm;
@@ -134,6 +137,7 @@ impl IrTypeFamily for Robust {
     type Ref<'itm> = Transparent;
     type RefMut<'itm> = Transparent;
     type Box = Box<Self>;
+    type SliceBox = Box<[Self]>;
     type SliceRef<'itm> = &'itm [Self];
     type SliceRefMut<'itm> = &'itm mut [Self];
     type Vec = Vec<Self>;
@@ -143,6 +147,7 @@ impl IrTypeFamily for Opaque {
     type Ref<'itm> = Transparent;
     type RefMut<'itm> = Transparent;
     type Box = Box<Self>;
+    type SliceBox = Box<[Self]>;
     type SliceRef<'itm> = &'itm [Self];
     type SliceRefMut<'itm> = &'itm mut [Self];
     type Vec = Vec<Self>;
@@ -152,6 +157,7 @@ impl IrTypeFamily for Transparent {
     type Ref<'itm> = Self;
     type RefMut<'itm> = Self;
     type Box = Box<Self>;
+    type SliceBox = Box<[Self]>;
     type SliceRef<'itm> = &'itm [Self];
     type SliceRefMut<'itm> = &'itm mut [Self];
     type Vec = Vec<Self>;
@@ -161,6 +167,7 @@ impl IrTypeFamily for &Extern {
     type Ref<'itm> = &'itm Self where Self: 'itm;
     type RefMut<'itm> = &'itm mut Self where Self: 'itm;
     type Box = Box<Self>;
+    type SliceBox = Box<[Self]>;
     type SliceRef<'itm> = &'itm [Self] where Self: 'itm;
     type SliceRefMut<'itm> = &'itm mut [Self] where Self: 'itm;
     type Vec = Vec<Self>;
@@ -170,6 +177,7 @@ impl IrTypeFamily for &mut Extern {
     type Ref<'itm> = &'itm Self where Self: 'itm;
     type RefMut<'itm> = &'itm mut Self where Self: 'itm;
     type Box = Box<Self>;
+    type SliceBox = Box<[Self]>;
     type SliceRef<'itm> = &'itm [Self] where Self: 'itm;
     type SliceRefMut<'itm> = &'itm mut [Self] where Self: 'itm;
     type Vec = Vec<Self>;
@@ -209,6 +217,12 @@ where
 {
     type Type = <R::Type as IrTypeFamily>::Box;
 }
+impl<R: Ir> Ir for Box<[R]>
+where
+    R::Type: IrTypeFamily,
+{
+    type Type = <R::Type as IrTypeFamily>::SliceBox;
+}
 impl<'itm, R: Ir> Ir for &'itm [R]
 where
     R::Type: IrTypeFamily,

ffi/src/repr_c.rs

@@ -687,6 +687,53 @@ impl<R: ReprC> COutPtrRead<Box<Robust>> for Box<R> {
     }
 }
 
+impl<R: ReprC> CType<Box<[Robust]>> for Box<[R]> {
+    type ReprC = SliceMut<R>;
+}
+impl<R: ReprC> CTypeConvert<'_, Box<[Robust]>, SliceMut<R>> for Box<[R]> {
+    type RustStore = Self;
+    type FfiStore = ();
+
+    fn into_repr_c(self, store: &mut Self::RustStore) -> SliceMut<R> {
+        *store = self;
+        SliceMut::from_slice(Some(store.as_mut()))
+    }
+
+    unsafe fn try_from_repr_c(source: SliceMut<R>, _: &mut ()) -> Result<Self> {
+        source
+            .into_rust()
+            .ok_or(FfiReturn::ArgIsNull)
+            .map(|slice| (&*slice).into())
+    }
+}
+
+impl<R: ReprC> CWrapperType<Box<[Robust]>> for Box<[R]> {
+    type InputType = Self;
+    type ReturnType = Self;
+}
+impl<R: ReprC> COutPtr<Box<[Robust]>> for Box<[R]> {
+    type OutPtr = OutBoxedSlice<R>;
+}
+impl<R: ReprC> COutPtrWrite<Box<[Robust]>> for Box<[R]> {
+    unsafe fn write_out(self, out_ptr: *mut Self::OutPtr) {
+        let mut store = Box::default();
+        CTypeConvert::<Box<[Robust]>, _>::into_repr_c(self, &mut store);
+        out_ptr.write(OutBoxedSlice::from_boxed_slice(Some(store)));
+    }
+}
+impl<R: ReprC> COutPtrRead<Box<[Robust]>> for Box<[R]> {
+    unsafe fn try_read_out(out_ptr: Self::OutPtr) -> Result<Self> {
+        let slice = SliceMut::from_raw_parts_mut(out_ptr.as_mut_ptr(), out_ptr.len());
+        let res = CTypeConvert::<Box<[Robust]>, _>::try_from_repr_c(slice, &mut ());
+
+        if !out_ptr.deallocate() {
+            return Err(FfiReturn::TrapRepresentation);
+        }
+
+        res
+    }
+}
+
 impl<R: ReprC> CType<&[Robust]> for &[R] {
     type ReprC = SliceRef<R>;
 }
@@ -868,6 +915,50 @@ impl<R> COutPtrWrite<Box<Opaque>> for Box<R> {
     }
 }
 
+impl<R> CType<Box<[Opaque]>> for Box<[R]> {
+    type ReprC = SliceMut<*mut R>;
+}
+impl<R> CTypeConvert<'_, Box<[Opaque]>, SliceMut<*mut R>> for Box<[R]> {
+    type RustStore = Box<[*mut R]>;
+    type FfiStore = ();
+
+    fn into_repr_c(self, store: &mut Self::RustStore) -> SliceMut<*mut R> {
+        *store = Vec::from(self)
+            .into_iter()
+            .map(|a: R| Box::new(a))
+            .map(Box::into_raw)
+            .collect();
+
+        SliceMut::from_slice(Some(store))
+    }
+
+    unsafe fn try_from_repr_c(source: SliceMut<*mut R>, _: &mut ()) -> Result<Self> {
+        source
+            .into_rust()
+            .ok_or(FfiReturn::ArgIsNull)?
+            .iter()
+            .map(|&item| {
+                if let Some(item) = item.as_mut() {
+                    return Ok(*Box::from_raw(item));
+                }
+
+                Err(FfiReturn::ArgIsNull)
+            })
+            .collect::<core::result::Result<_, _>>()
+    }
+}
+
+impl<R> COutPtr<Box<[Opaque]>> for Box<[R]> {
+    type OutPtr = OutBoxedSlice<*mut R>;
+}
+impl<R> COutPtrWrite<Box<[Opaque]>> for Box<[R]> {
+    unsafe fn write_out(self, out_ptr: *mut Self::OutPtr) {
+        let mut store = Box::default();
+        CTypeConvert::<Box<[Opaque]>, _>::into_repr_c(self, &mut store);
+        out_ptr.write(OutBoxedSlice::from_boxed_slice(Some(store)));
+    }
+}
+
 impl<R> CType<&[Opaque]> for &[R] {
     type ReprC = SliceRef<*const R>;
 }
@@ -1081,6 +1172,10 @@ impl<'itm, R: External> CWrapperType<Box<&'itm Extern>> for Box<&'itm R> {
     type InputType = Box<R::RefType<'itm>>;
     type ReturnType = Box<R::RefType<'itm>>;
 }
+impl<'itm, R: External> CWrapperType<Box<[&'itm Extern]>> for Box<[&'itm R]> {
+    type InputType = Box<[R::RefType<'itm>]>;
+    type ReturnType = Box<[R::RefType<'itm>]>;
+}
 impl<'itm, R: External> CWrapperType<&'itm [&'itm Extern]> for &'itm [&'itm R] {
     type InputType = &'itm [R::RefType<'itm>];
     type ReturnType = &'itm [R::RefType<'itm>];
@@ -1106,6 +1201,10 @@ impl<'itm, R: External> CWrapperType<Box<&'itm mut Extern>> for Box<&'itm mut R>
     type InputType = Box<R::RefMutType<'itm>>;
     type ReturnType = Box<R::RefMutType<'itm>>;
 }
+impl<'itm, R: External> CWrapperType<Box<[&'itm mut Extern]>> for Box<[&'itm mut R]> {
+    type InputType = Box<[R::RefMutType<'itm>]>;
+    type ReturnType = Box<[R::RefMutType<'itm>]>;
+}
 impl<'itm, R: External> CWrapperType<&'itm [&'itm mut Extern]> for &'itm [&'itm mut R] {
     type InputType = &'itm [R::RefMutType<'itm>];
     type ReturnType = &'itm [R::RefMutType<'itm>];
@@ -1269,6 +1368,63 @@ where
     }
 }
 
+impl<R: Transmute> CType<Box<[Transparent]>> for Box<[R]>
+where
+    Box<[R::Target]>: FfiType,
+{
+    type ReprC = <Box<[R::Target]> as FfiType>::ReprC;
+}
+impl<'itm, R: Transmute, C: ReprC> CTypeConvert<'itm, Box<[Transparent]>, C> for Box<[R]>
+where
+    Box<[R::Target]>: FfiConvert<'itm, C>,
+{
+    type RustStore = <Box<[R::Target]> as FfiConvert<'itm, C>>::RustStore;
+    type FfiStore = <Box<[R::Target]> as FfiConvert<'itm, C>>::FfiStore;
+
+    fn into_repr_c(self, store: &'itm mut Self::RustStore) -> C {
+        transmute_into_target_boxed_slice(self).into_ffi(store)
+    }
+
+    unsafe fn try_from_repr_c(source: C, store: &'itm mut Self::FfiStore) -> Result<Self> {
+        <Box<[R::Target]>>::try_from_ffi(source, store)
+            .and_then(|output| transmute_from_target_boxed_slice(output))
+    }
+}
+
+impl<R: Transmute> CWrapperType<Box<[Transparent]>> for Box<[R]>
+where
+    Box<[R::Target]>: FfiWrapperType,
+    <Box<[R::Target]> as FfiWrapperType>::InputType: WrapperTypeOf<Self>,
+    <Box<[R::Target]> as FfiWrapperType>::ReturnType: WrapperTypeOf<Self>,
+{
+    type InputType = <<Box<[R::Target]> as FfiWrapperType>::InputType as WrapperTypeOf<Self>>::Type;
+    type ReturnType =
+        <<Box<[R::Target]> as FfiWrapperType>::ReturnType as WrapperTypeOf<Self>>::Type;
+}
+impl<R: Transmute> COutPtr<Box<[Transparent]>> for Box<[R]>
+where
+    Box<[R::Target]>: FfiOutPtr,
+{
+    type OutPtr = <Box<[R::Target]> as FfiOutPtr>::OutPtr;
+}
+impl<R: Transmute> COutPtrWrite<Box<[Transparent]>> for Box<[R]>
+where
+    Box<[R::Target]>: FfiOutPtrWrite,
+{
+    unsafe fn write_out(self, out_ptr: *mut Self::OutPtr) {
+        FfiOutPtrWrite::write_out(transmute_into_target_boxed_slice(self), out_ptr);
+    }
+}
+impl<R: Transmute> COutPtrRead<Box<[Transparent]>> for Box<[R]>
+where
+    Box<[R::Target]>: FfiOutPtrRead,
+{
+    unsafe fn try_read_out(out_ptr: Self::OutPtr) -> Result<Self> {
+        <Box<[R::Target]>>::try_read_out(out_ptr)
+            .and_then(|output| transmute_from_target_boxed_slice(output))
+    }
+}
+
 impl<'slice, R: Transmute> CType<&'slice [Transparent]> for &'slice [R]
 where
     &'slice [R::Target]: FfiType,
@@ -1453,6 +1609,11 @@ unsafe impl<R: Transmute> NonLocal<Box<Transparent>> for Box<R> where
 {
 }
 // SAFETY: Type doesn't return a reference to the store if the inner type doesn't
+unsafe impl<R: Transmute> NonLocal<Box<[Transparent]>> for Box<[R]> where
+    Box<[R::Target]>: Ir + NonLocal<<Box<[R::Target]> as Ir>::Type>
+{
+}
+// SAFETY: Type doesn't return a reference to the store if the inner type doesn't
 unsafe impl<'slice, R: Transmute> NonLocal<&'slice [Transparent]> for &'slice [R] where
     &'slice [R::Target]: Ir + NonLocal<<&'slice [R::Target] as Ir>::Type>
 {
@@ -1506,6 +1667,26 @@ unsafe fn transmute_from_target_box<R: Transmute>(source: Box<R::Target>) -> Res
     Ok(Box::from_raw(Box::into_raw(source).cast::<R>()))
 }
 
+#[allow(clippy::boxed_local)]
+fn transmute_into_target_boxed_slice<R: Transmute>(mut source: Box<[R]>) -> Box<[R::Target]> {
+    let (ptr, len) = (source.as_mut_ptr().cast::<R::Target>(), source.len());
+    // SAFETY: `R` is guaranteed to be transmutable into `R::Target`
+    unsafe { Box::from_raw(core::slice::from_raw_parts_mut(ptr, len)) }
+}
+#[allow(clippy::boxed_local)]
+unsafe fn transmute_from_target_boxed_slice<R: Transmute>(
+    mut source: Box<[R::Target]>,
+) -> Result<Box<[R]>> {
+    if !source.iter().all(|item| R::is_valid(item)) {
+        return Err(FfiReturn::TrapRepresentation);
+    }
+
+    Ok(Box::from_raw(core::slice::from_raw_parts_mut(
+        source.as_mut_ptr().cast(),
+        source.len(),
+    )))
+}
+
 fn transmute_into_target_slice_ref<R: Transmute>(source: &[R]) -> &[R::Target] {
     let (ptr, len) = (source.as_ptr().cast::<R::Target>(), source.len());
     // SAFETY: `R` is guaranteed to be transmutable into `R::Target`

ffi/src/slice.rs

@@ -165,6 +165,17 @@ impl<C: ReprC> OutBoxedSlice<C> {
         self.1
     }
 
+    /// Create [`Self`] from a `Box<[T]>`
+    pub fn from_boxed_slice(source: Option<Box<[C]>>) -> Self {
+        source.map_or_else(
+            || Self(core::ptr::null_mut(), 0),
+            |boxed_slice| {
+                let mut boxed_slice = core::mem::ManuallyDrop::new(boxed_slice);
+                Self(boxed_slice.as_mut_ptr(), boxed_slice.len())
+            },
+        )
+    }
+
     /// Create [`Self`] from a `Vec<T>`
     pub fn from_vec(source: Option<Vec<C>>) -> Self {
         source.map_or_else(

ffi/tests/ffi_export.rs

@@ -128,6 +128,12 @@ impl OpaqueStruct {
     }
 }
 
+#[ffi_export]
+/// Take and return boxed slice
+pub fn freestanding_with_boxed_slice(item: Box<[u8]>) -> Box<[u8]> {
+    item
+}
+
 #[ffi_export]
 /// Take and return byte
 pub fn freestanding_with_option(item: Option<u8>) -> Option<u8> {
@@ -428,6 +434,29 @@ fn return_option() {
     }
 }
 
+#[test]
+#[webassembly_test::webassembly_test]
+fn take_and_return_boxed_slice() {
+    let input: Box<[u8]> = [12u8, 42u8].into();
+    let mut output = MaybeUninit::new(OutBoxedSlice::from_raw_parts(core::ptr::null_mut(), 0));
+    let mut in_store = Default::default();
+
+    unsafe {
+        assert_eq!(
+            FfiReturn::Ok,
+            __freestanding_with_boxed_slice(
+                FfiConvert::into_ffi(input, &mut in_store),
+                output.as_mut_ptr()
+            )
+        );
+
+        let output = output.assume_init();
+        assert_eq!(output.len(), 2);
+        let boxed_slice = Box::<[u8]>::try_read_out(output).expect("Valid");
+        assert_eq!(boxed_slice, [12u8, 42u8].into());
+    }
+}
+
 #[test]
 #[webassembly_test::webassembly_test]
 fn take_and_return_option_without_niche() {