Enum FlexFuture 

pub enum FlexFuture<T> {
    Ready(Ready<T>),
    Pending(Pending<T>),
    Generic(Pin<Box<dyn Future<Output = T>>>),
}

Future that either returns a precomputed value or delegates to a heap-allocated, type-erased future.

FlexFuture works as a selective wrapper for std::future::Ready, std::future::Pending, and a generic future in a Box. When a function needs to return a future, it can use FlexFuture to possibly avoid heap allocation if the future is already known to be ready.

This type does not have a lifetime parameter, so the contained future must have a 'static lifetime. This is because FlexFuture is also used in SharedSystem, which performs dynamic lifetime checking to access its internal state guarded by a RefCell. Instead of borrowing the system, the future must share ownership of the system to keep it alive until the future is resolved.

Variants

Ready(Ready<T>)

Future that is already ready with a value

Pending(Pending<T>)

Future that is pending and will never resolve

Generic(Pin<Box<dyn Future<Output = T>>>)

Heap-allocated, type-erased future

Implementations

impl<T> FlexFuture<T>

pub fn boxed<F>(f: F) -> Self

where F: Future<Output = T> + 'static,

Creates a new FlexFuture from any future.

This function allocates memory for the future. If the future is already allocated on the heap, use FlexFuture::from instead.

pub fn into_boxed(self) -> Pin<Box<dyn Future<Output = T>>>

where T: 'static,

Converts this FlexFuture into a Pin<Box<dyn Future<Output = T>>.

Trait Implementations

impl<T: Debug> Debug for FlexFuture<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> From<Box<dyn Future<Output = T>>> for FlexFuture<T>

fn from(future: Box<dyn Future<Output = T>>) -> Self

Converts to this type from the input type.

impl<T: 'static> From<FlexFuture<T>> for Pin<Box<dyn Future<Output = T>>>

fn from(future: FlexFuture<T>) -> Self

Converts to this type from the input type.

impl<T> From<Pending<T>> for FlexFuture<T>

fn from(pending: Pending<T>) -> Self

Converts to this type from the input type.

impl<T> From<Pin<Box<dyn Future<Output = T>>>> for FlexFuture<T>

fn from(future: Pin<Box<dyn Future<Output = T>>>) -> Self

Converts to this type from the input type.

impl<T> From<Ready<T>> for FlexFuture<T>

fn from(ready: Ready<T>) -> Self

Converts to this type from the input type.

impl<T> From<T> for FlexFuture<T>

fn from(value: T) -> Self

Converts to this type from the input type.

impl<T> Future for FlexFuture<T>

type Output = T

The type of value produced on completion.

fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T>

Attempts to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.