1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39

use core::marker::Unpin;
use core::mem::PinMut;
use futures_core::future::Future;
use futures_core::task::{self, Poll};

/// A future that is immediately ready with a value
///
/// Created by the [`ready()`] function.
#[derive(Debug, Clone)]
#[must_use = "futures do nothing unless polled"]
pub struct Ready<T>(Option<T>);

impl<T> Unpin for Ready<T> {}

impl<T> Future for Ready<T> {
    type Output = T;

    #[inline]
    fn poll(mut self: PinMut<Self>, _cx: &mut task::Context) -> Poll<T> {
        Poll::Ready(self.0.take().unwrap())
    }
}

/// Create a future that is immediately ready with a value.
///
/// # Examples
///
/// ```
/// #![feature(async_await, await_macro, futures_api)]
/// # futures::executor::block_on(async {
/// use futures::future;
///
/// let a = future::ready(1);
/// assert_eq!(await!(a), 1);
/// # });
/// ```
pub fn ready<T>(t: T) -> Ready<T> {
    Ready(Some(t))
}