From 7bd8e3ef63330e870cf4644d21c285cce35c703d Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 31 Oct 2024 09:56:15 +0100 Subject: rust: qom: split ObjectType from ObjectImpl trait Define a separate trait for fields that also applies to classes that are defined by C code. This makes it possible to add metadata to core classes, which has multiple uses: - it makes it possible to access the parent struct's TYPE_* for types that are defined in Rust code, and to avoid repeating it in every subclass - implementors of ObjectType will be allowed to implement the IsA<> trait and therefore to perform typesafe casts from one class to another. - in the future, an ObjectType could be created with Foo::new() in a type-safe manner, without having to pass a TYPE_* constant. Reviewed-by: Zhao Liu Signed-off-by: Paolo Bonzini --- rust/qemu-api/src/definitions.rs | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) (limited to 'rust/qemu-api/src/definitions.rs') diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs index f297075898..b98a692678 100644 --- a/rust/qemu-api/src/definitions.rs +++ b/rust/qemu-api/src/definitions.rs @@ -26,25 +26,40 @@ unsafe extern "C" fn rust_instance_post_init(obj: *mut Object) { T::INSTANCE_POST_INIT.unwrap()(unsafe { &mut *obj.cast::() }) } -/// Trait a type must implement to be registered with QEMU. +/// Trait exposed by all structs corresponding to QOM objects. /// /// # Safety /// -/// - the struct must be `#[repr(C)]` +/// For classes declared in C: +/// +/// - `Class` and `TYPE` must match the data in the `TypeInfo`; +/// +/// - the first field of the struct must be of the instance type corresponding +/// to the superclass, as declared in the `TypeInfo` +/// +/// - likewise, the first field of the `Class` struct must be of the class type +/// corresponding to the superclass /// -/// - `Class` and `TYPE` must match the data in the `TypeInfo` (this is -/// automatic if the class is defined via `ObjectImpl`). +/// For classes declared in Rust and implementing [`ObjectImpl`]: +/// +/// - the struct must be `#[repr(C)]`; /// /// - the first field of the struct must be of the instance struct corresponding -/// to the superclass declared as `PARENT_TYPE_NAME` -pub trait ObjectImpl: ClassInitImpl + Sized { +/// to the superclass, as declared in `ObjectImpl::PARENT_TYPE_NAME` +/// +/// - likewise, the first field of the `Class` must be of the class struct +/// corresponding to the superclass +pub unsafe trait ObjectType: Sized { /// The QOM class object corresponding to this struct. Not used yet. type Class; /// The name of the type, which can be passed to `object_new()` to /// generate an instance of this type. const TYPE_NAME: &'static CStr; +} +/// Trait a type must implement to be registered with QEMU. +pub trait ObjectImpl: ObjectType + ClassInitImpl { /// The parent of the type. This should match the first field of /// the struct that implements `ObjectImpl`: const PARENT_TYPE_NAME: Option<&'static CStr>; -- cgit 1.4.1