From f50cd85c8475c16374d0e138efda222ce4455f53 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 19 Dec 2024 14:32:16 +0100 Subject: rust: qom: add casting functionality Add traits that let client cast typecast safely between object types. In particular, an upcast is compile-time guaranteed to succeed, and a YOLO C-style downcast must be marked as unsafe. The traits are based on an IsA<> trait that declares what is a subclass of what, which is an idea taken from glib-rs (https://docs.rs/glib/latest/glib/object/trait.IsA.html). The four primitives are also taken from there (https://docs.rs/glib/latest/glib/object/trait.Cast.html). However, the implementation of casting itself is a bit different and uses the Deref trait. This removes some pointer arithmetic from the pl011 device; it is also a prerequisite for the definition of methods, so that they can be invoked on all subclass structs. This will use the IsA<> trait to detect the structs that support the methods. glib also has a "monadic" casting trait which could be implemented on Option (as in https://docs.rs/glib/latest/glib/object/trait.CastNone.html) and perhaps even Result. For now I'm leaving it out, as the patch is already big enough and the benefit seems debatable. Reviewed-by: Zhao Liu Signed-off-by: Paolo Bonzini --- rust/qemu-api/src/qdev.rs | 1 + 1 file changed, 1 insertion(+) (limited to 'rust/qemu-api/src/qdev.rs') diff --git a/rust/qemu-api/src/qdev.rs b/rust/qemu-api/src/qdev.rs index 07a502a837..686054e737 100644 --- a/rust/qemu-api/src/qdev.rs +++ b/rust/qemu-api/src/qdev.rs @@ -144,3 +144,4 @@ unsafe impl ObjectType for DeviceState { const TYPE_NAME: &'static CStr = unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_DEVICE) }; } +qom_isa!(DeviceState: Object); -- cgit 1.4.1