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| author | Paolo Bonzini <pbonzini@redhat.com> | 2025-02-14 11:13:53 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2025-03-06 12:44:46 +0100 |
| commit | f07a5674cf97b8473e5d06d7b1df9b51e97d553f (patch) | |
| tree | 347e41799050dca47ddc510ff46d3a99cf0b5580 /rust/qemu-api/src/cell.rs | |
| parent | 0b9d05e3c98fe168f3502ccc422b9171467314fa (diff) | |
| download | qemu-f07a5674cf97b8473e5d06d7b1df9b51e97d553f.zip qemu-f07a5674cf97b8473e5d06d7b1df9b51e97d553f.tar.gz qemu-f07a5674cf97b8473e5d06d7b1df9b51e97d553f.tar.bz2 | |
rust: qemu_api_macros: add Wrapper derive macro
Add a derive macro that makes it easy to peel off all the layers of
specialness (UnsafeCell, MaybeUninit, etc.) and just get a pointer
to the wrapped type; and likewise add them back starting from a
*mut.
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'rust/qemu-api/src/cell.rs')
| -rw-r--r-- | rust/qemu-api/src/cell.rs | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/rust/qemu-api/src/cell.rs b/rust/qemu-api/src/cell.rs index 2889abb..448638e 100644 --- a/rust/qemu-api/src/cell.rs +++ b/rust/qemu-api/src/cell.rs @@ -1030,3 +1030,48 @@ impl<T: Default> Opaque<T> { } } } + +/// Annotates [`Self`] as a transparent wrapper for another type. +/// +/// Usually defined via the [`qemu_api_macros::Wrapper`] derive macro. +/// +/// # Examples +/// +/// ``` +/// # use std::mem::ManuallyDrop; +/// # use qemu_api::cell::Wrapper; +/// #[repr(transparent)] +/// pub struct Example { +/// inner: ManuallyDrop<String>, +/// } +/// +/// unsafe impl Wrapper for Example { +/// type Wrapped = String; +/// } +/// ``` +/// +/// # Safety +/// +/// `Self` must be a `#[repr(transparent)]` wrapper for the `Wrapped` type, +/// whether directly or indirectly. +/// +/// # Methods +/// +/// By convention, types that implement Wrapper also implement the following +/// methods: +/// +/// ```ignore +/// pub const unsafe fn from_raw<'a>(value: *mut Self::Wrapped) -> &'a Self; +/// pub const unsafe fn as_mut_ptr(&self) -> *mut Self::Wrapped; +/// pub const unsafe fn as_ptr(&self) -> *const Self::Wrapped; +/// pub const unsafe fn raw_get(slot: *mut Self) -> *const Self::Wrapped; +/// ``` +/// +/// They are not defined here to allow them to be `const`. +pub unsafe trait Wrapper { + type Wrapped; +} + +unsafe impl<T> Wrapper for Opaque<T> { + type Wrapped = T; +} |