Provide a trait that can be used to invoke methods of the QOM object class. The trait extends Deref and has a blanket implementation for any type that dereferences to IsA<Object>. This way, it can be used on any struct that dereferences to Object or a subclass.
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> --- qemu/src/lib.rs | 2 + qemu/src/qom/object.rs | 92 ++++++++++++++++++++++++++++++++++++++++++ qemu/src/qom/refs.rs | 8 ++++ 3 files changed, 102 insertions(+) diff --git a/qemu/src/lib.rs b/qemu/src/lib.rs index 0d91623..a6e7b17 100644 --- a/qemu/src/lib.rs +++ b/qemu/src/lib.rs @@ -5,6 +5,8 @@ pub mod bindings; pub use bindings::Object; pub mod qom; +pub use qom::object::ObjectClassMethods; +pub use qom::object::ObjectMethods; pub use qom::object::ObjectType; pub use qom::refs::ObjectCast; pub use qom::refs::Owned; diff --git a/qemu/src/qom/object.rs b/qemu/src/qom/object.rs index bd6b957..4e84e29 100644 --- a/qemu/src/qom/object.rs +++ b/qemu/src/qom/object.rs @@ -2,12 +2,26 @@ //! //! @author Paolo Bonzini +use std::borrow::Cow; use std::ffi::CStr; +use std::fmt; +use std::ops::Deref; +use crate::bindings::object_get_typename; +use crate::bindings::object_property_add_child; +use crate::bindings::object_new; +use crate::bindings::object_unparent; use crate::bindings::Object; use crate::qom_isa; +use crate::qom::refs::IsA; +use crate::qom::refs::ObjectCast; +use crate::qom::refs::Owned; + +use crate::util::foreign::CloneToForeign; +use crate::util::foreign::FromForeign; + /// Trait exposed by all structs corresponding to QOM objects. /// Defines "class methods" for the class. Usually these can be /// implemented on the class itself; here, using a trait allows @@ -31,4 +45,82 @@ unsafe impl ObjectType for Object { const TYPE: &'static CStr = c"object"; } +// ------------------------------ +// Object class + qom_isa!(Object); + +/// Trait for class methods exposed by the Object class. The methods can be +/// called on all objects that have the trait `IsA<Object>`. +/// +/// The trait should only be used through the blanket implementation, +/// which guarantees safety via `IsA` + +pub trait ObjectClassMethods: IsA<Object> { + /// Return a new reference counted instance of this class + fn new() -> Owned<Self> { + // SAFETY: the object created by object_new is allocated on + // the heap and has a reference count of 1 + unsafe { + let obj = &*object_new(Self::TYPE.as_ptr()); + Owned::from_raw(obj.unsafe_cast::<Self>()) + } + } +} + +/// Trait for methods exposed by the Object class. The methods can be +/// called on all objects that have the trait `IsA<Object>`. +/// +/// The trait should only be used through the blanket implementation, +/// which guarantees safety via `IsA` +pub trait ObjectMethods: Deref +where + Self::Target: IsA<Object>, +{ + /// Return the name of the type of `self` + fn typename(&self) -> Cow<'_, str> { + let obj = self.upcast::<Object>(); + // SAFETY: safety of this is the requirement for implementing IsA + // The result of the C API has static lifetime + unsafe { + Cow::cloned_from_foreign(object_get_typename(obj.as_mut_ptr())) + } + } + + /// Add an object as a child of the receiver. + fn property_add_child<T: ObjectType>(&self, name: &str, child: Owned<T>) + { + let obj = self.upcast::<Object>(); + let name = name.clone_to_foreign(); + unsafe { + // SAFETY: casting to object is always safe even if `child`'s + // target type is an interface type + let child = child.unsafe_cast::<Object>(); + object_property_add_child(obj.as_mut_ptr(), + name.as_ptr(), + child.as_mut_ptr()); + + // object_property_add_child() added a reference of its own; + // dropping the one in `child` is the common case. + } + } + + /// Remove the object from the QOM tree + fn unparent(&self) { + let obj = self.upcast::<Object>(); + // SAFETY: safety of this is the requirement for implementing IsA + unsafe { + object_unparent(obj.as_mut_ptr()); + } + } + + /// Convenience function for implementing the Debug trait + fn debug_fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + f.debug_tuple(&self.typename()) + .field(&(self as *const Self)) + .finish() + } +} + +impl<R> ObjectClassMethods for R where R: IsA<Object> {} +impl<R: Deref> ObjectMethods for R where R::Target: IsA<Object> {} diff --git a/qemu/src/qom/refs.rs b/qemu/src/qom/refs.rs index a319bde..431ef0a 100644 --- a/qemu/src/qom/refs.rs +++ b/qemu/src/qom/refs.rs @@ -6,9 +6,11 @@ use crate::bindings::object_dynamic_cast; use crate::bindings::Object; use crate::bindings::{object_ref, object_unref}; +use crate::qom::object::ObjectMethods; use crate::qom::object::ObjectType; use std::borrow::Borrow; +use std::fmt::{self, Debug}; use std::mem::ManuallyDrop; use std::ops::Deref; use std::ptr::NonNull; @@ -272,3 +274,9 @@ impl<T: ObjectType> Drop for Owned<T> { } } } + +impl<T: IsA<Object>> Debug for Owned<T> { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + self.deref().debug_fmt(f) + } +} -- 2.45.2