Crate vtable[−][src]
Expand description
This crate allows you to create ffi-friendly virtual tables.
Features
- A
#[vtable]
macro to annotate a VTable struct to generate the traits and structure to safely work with it. VRef
/VRefMut
/VBox
types. They are fat reference/box types which wrap a pointer to the vtable, and a pointer to the object.VRc
/VWeak
types: equivalent tostd::rc::{Rc, Weak}
types but works with a vtable pointer.- Ability to store constants in a vtable.
- These constants can even be a field offset.
Example of use:
use vtable::*;
// we are going to declare a VTable structure for an Animal trait
#[vtable]
#[repr(C)]
struct AnimalVTable {
/// pointer to a function that makes a noise. The `VRef<AnimalVTable>` is the type of
/// the self object.
///
/// Note: the #[vtable] macro will automatically add `extern "C"` if that is missing.
make_noise: fn(VRef<AnimalVTable>, i32) -> i32,
/// if there is a 'drop' member, it is considered as the destructor.
drop: fn(VRefMut<AnimalVTable>),
}
struct Dog(i32);
// The #[vtable] macro created the Animal Trait
impl Animal for Dog {
fn make_noise(&self, intensity: i32) -> i32 {
println!("Wof!");
return self.0 * intensity;
}
}
// the vtable macro also exposed a macro to create a vtable
AnimalVTable_static!(static DOG_VT for Dog);
// with that, it is possible to instantiate a VBox
let animal_box = VBox::<AnimalVTable>::new(Dog(42));
assert_eq!(animal_box.make_noise(2), 42 * 2);
The #[vtable]
macro created the “Animal” trait.
Note that the #[vtable]
macro is applied to the VTable struct so
that cbindgen
can see the actual vtable.
Re-exports
pub use const_field_offset::*;
Macros
Structs
Similar to std::alloc::Layout
, but repr(C)
An equivalent of a Box that holds a pointer to a VTable and a pointer to an instance. A VBox frees the instance when dropped.
Represents an offset to a field of type matching the vtable, within the Base container structure.
A reference counted pointer to an object matching the virtual table T
VRcMapped allows bundling a VRc of a type along with a reference to an object that’s
reachable through the data the VRc owns and that satisfies the requirements of a Pin.
VRCMapped is constructed using VRc::map
and, like VRc, has a weak counterpart, VWeakMapped
.
VRef<'a MyTraitVTable>
can be thought as a &'a dyn MyTrait
VRefMut<'a MyTraitVTable>
can be thought as a &'a mut dyn MyTrait
VWeakMapped allows bundling a VWeak with a reference to an object that’s reachable
from the object a successfully upgraded VWeak points to. VWeakMapped’s API consists
only of the ability to create clones and to attempt upgrading back to a VRcMapped
.
Traits
Allow to associate a VTable with a type.
Internal trait that is implemented by the #[vtable]
macro.
This trait is implemented by the #[vtable]
macro.
This trait is implemented by the #[vtable]
macro.
Attribute Macros
This macro needs to be applied to a VTable structure