zr/
opaque_bytes.rs

1// Copyright 2026 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use crate::opaque::Opaque;
6
7/// A generic, safe opaque storage container with exact const size constraints.
8///
9/// This integrates with `Opaque<T>` to guarantee the Rust compiler knows the underlying memory
10/// is interior-mutable (via `UnsafeCell`) and potentially uninitialized (via `MaybeUninit`).
11pub type OpaqueBytes<const SIZE: usize> = Opaque<[u8; SIZE]>;
12
13/// Defines an opaque C++ storage type with explicit size, alignment, and an FFI `init` function.
14#[macro_export]
15macro_rules! define_opaque_storage_ffi {
16    (
17        $(#[$meta:meta])*
18        $vis:vis struct $name:ident(
19            $size:expr,
20            $align_const:expr,
21            $align_literal:literal,
22            $ffi_fn:path
23            $(, $arg:ident : $arg_ty:ty)* $(,)?
24        );
25    ) => {
26        $(#[$meta])*
27        #[repr(C, align($align_literal))]
28        $vis struct $name {
29            inner: $crate::OpaqueBytes<{$size}>,
30            _pinned: ::core::marker::PhantomPinned,
31        }
32
33        $crate::static_assert_size_and_align!($name, $size, $align_const);
34
35        impl $name {
36            $vis unsafe fn init(
37                $( $arg : $arg_ty ),*
38            ) -> impl ::pin_init::PinInit<Self, ::core::convert::Infallible> {
39                $crate::pin_init_ffi!($ffi_fn $(, $arg)*)
40            }
41
42            /// Returns a raw void pointer to the underlying storage.
43            $vis fn as_void_ptr(&self) -> *mut ::core::ffi::c_void {
44                self.inner.get() as *mut ::core::ffi::c_void
45            }
46        }
47    };
48}
zr/opaque_bytes.rs

zr/
opaque_bytes.rs
