[−][src]Crate vtable

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 to std::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

new_vref

Creates a VRef or a VRefMut suitable for an instance that implements the trait

Structs

Dyn	This is a marker type to be used in `VRc` and `VWeak` to mean that the actual type is now known.
Layout	Similar to `std::alloc::Layout`, but `repr(C)`
VBox	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.
VOffset	Represents an offset to a field of type matching the vtable, within the Base container structure.
VRc	A reference counted pointer to an object matching the virtual table `T`
VRef	`VRef<'a MyTraitVTable>` can be thought as a `&'a dyn MyTrait`
VRefMut	`VRefMut<'a MyTraitVTable>` can be thought as a `&'a mut dyn MyTrait`
VWeak	Weak pointer for the `VRc` where `VTable` is a VTable struct, and `X` is the type of the instance, or `Dyn` if it is not known

Traits

HasStaticVTable	Allow to associate a VTable with a type.
VTableMeta	Internal trait that is implemented by the `#[vtable]` macro.
VTableMetaDrop	This trait is implemented by the `#[vtable]` macro.
VTableMetaDropInPlace	This trait is implemented by the `#[vtable]` macro.

Attribute Macros

vtable

This macro needs to be applied to a VTable structure