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/// A macro for extracting the successful type of a `Poll<T, E>`.
///
/// This macro bakes propagation of both errors and `NotReady` signals by
/// returning early.
#[macro_export]
macro_rules! try_ready {
($e:expr) => (match $e {
Ok($crate::Async::Ready(t)) => t,
Ok($crate::Async::NotReady) => return Ok($crate::Async::NotReady),
Err(e) => return Err(From::from(e)),
})
}
/// Return type of the `Future::poll` method, indicates whether a future's value
/// is ready or not.
///
/// * `Ok(Async::Ready(t))` means that a future has successfully resolved
/// * `Ok(Async::NotReady)` means that a future is not ready to complete yet
/// * `Err(e)` means that a future has completed with the given failure
pub type Poll<T, E> = Result<Async<T>, E>;
/// Return type of future, indicating whether a value is ready or not.
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum Async<T> {
/// Represents that a value is immediately ready.
Ready(T),
/// Represents that a value is not ready yet, but may be so later.
NotReady,
}
impl<T> Async<T> {
/// Change the success value of this `Async` with the closure provided
pub fn map<F, U>(self, f: F) -> Async<U>
where F: FnOnce(T) -> U
{
match self {
Async::Ready(t) => Async::Ready(f(t)),
Async::NotReady => Async::NotReady,
}
}
/// Returns whether this is `Async::Ready`
pub fn is_ready(&self) -> bool {
match *self {
Async::Ready(_) => true,
Async::NotReady => false,
}
}
/// Returns whether this is `Async::NotReady`
pub fn is_not_ready(&self) -> bool {
!self.is_ready()
}
}
impl<T> From<T> for Async<T> {
fn from(t: T) -> Async<T> {
Async::Ready(t)
}
}
/// The result of an asynchronous attempt to send a value to a sink.
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum AsyncSink<T> {
/// The `start_send` attempt succeeded, so the sending process has
/// *started*; you must use `Sink::poll_complete` to drive the send
/// to completion.
Ready,
/// The `start_send` attempt failed due to the sink being full. The value
/// being sent is returned, and the current `Task` will be automatically
/// notified again once the sink has room.
NotReady(T),
}
impl<T> AsyncSink<T> {
/// Change the NotReady value of this `AsyncSink` with the closure provided
pub fn map<F, U>(self, f: F) -> AsyncSink<U>
where F: FnOnce(T) -> U,
{
match self {
AsyncSink::Ready => AsyncSink::Ready,
AsyncSink::NotReady(t) => AsyncSink::NotReady(f(t)),
}
}
/// Returns whether this is `AsyncSink::Ready`
pub fn is_ready(&self) -> bool {
match *self {
AsyncSink::Ready => true,
AsyncSink::NotReady(_) => false,
}
}
/// Returns whether this is `AsyncSink::NotReady`
pub fn is_not_ready(&self) -> bool {
!self.is_ready()
}
}
/// Return type of the `Sink::start_send` method, indicating the outcome of a
/// send attempt. See `AsyncSink` for more details.
pub type StartSend<T, E> = Result<AsyncSink<T>, E>;
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