Struct UnsizedEnum

#[repr(C)]
pub struct UnsizedEnum<B, V0: ?Sized, V1> { /* private fields */ }

An unsized enum with two variants

As this is a DST, this enum can only be created on the heap. So for convenience, it allows a common base structure to be included in the header before the enum variants. Also, since a lot of space will generally be wasted by the discriminant due to alignment and packing (even if it is only a u8), a whole usize is used and the higher bits in the discriminant are made available to the caller for storage.

The type parameters are: the common base type, the first variant (which may be unsized) and the second variant (which must be sized).

Implementations

impl<B, V0, V1> UnsizedEnum<B, V0, V1>

pub fn new_v0(base: B, val: V0) -> Box<Self>

Create a new instance of the V0 type

pub fn new_v1(base: B, val: V1) -> Box<Self>

Create a new instance of the V1 type

impl<B, V0: ?Sized, V1> UnsizedEnum<B, V0, V1>

pub fn base(&mut self) -> &mut B

Return a mutable reference to the common base structure B

pub fn set_spare(&mut self, spare: usize)

Set a value in the spare bits above the discriminant. Bit 0 of this value will not be stored.

pub fn get_spare(&self) -> usize

Gets the discriminant value including any value stored in the spare bits above it. So bit 0 will be the disriminant (0 for V0, 1 for V1), and the remaining bits will be whatever value was saved by the most recent call to set_spare, or 0 initially.

pub fn set_v0(&mut self, v0: &Move<V0>)

Change the value stored in the enum to the provided V0 value, dropping the previous value (of whichever variant).

pub fn set_v1(&mut self, v1: V1)

Change the value stored in the enum to the provided V1 value, dropping the previous value (of whichever variant)

pub fn get_mut(&mut self) -> EnumRef<'_, V0, V1>

Get a reference to the value. Since there are two possible variants, an enum is returned that provides either one reference or the other.

Trait Implementations

impl<B, V0: ?Sized, V1> Drop for UnsizedEnum<B, V0, V1>

fn drop(&mut self)

Executes the destructor for this type.