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
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
use core::future::{poll_fn, Future};
use core::pin::Pin;
use core::task::{Context, Poll};

use futures_util::future::{select, Either};
use futures_util::stream::FusedStream;
use futures_util::{pin_mut, Stream};

use crate::{Duration, Instant};

/// Error returned by [`with_timeout`] on timeout.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "defmt", derive(defmt::Format))]
pub struct TimeoutError;

/// Runs a given future with a timeout.
///
/// If the future completes before the timeout, its output is returned. Otherwise, on timeout,
/// work on the future is stopped (`poll` is no longer called), the future is dropped and `Err(TimeoutError)` is returned.
pub async fn with_timeout<F: Future>(timeout: Duration, fut: F) -> Result<F::Output, TimeoutError> {
    let timeout_fut = Timer::after(timeout);
    pin_mut!(fut);
    match select(fut, timeout_fut).await {
        Either::Left((r, _)) => Ok(r),
        Either::Right(_) => Err(TimeoutError),
    }
}

/// A future that completes at a specified [Instant](struct.Instant.html).
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct Timer {
    expires_at: Instant,
    yielded_once: bool,
}

impl Timer {
    /// Expire at specified [Instant](struct.Instant.html)
    pub fn at(expires_at: Instant) -> Self {
        Self {
            expires_at,
            yielded_once: false,
        }
    }

    /// Expire after specified [Duration](struct.Duration.html).
    /// This can be used as a `sleep` abstraction.
    ///
    /// Example:
    /// ``` no_run
    /// use embassy_time::{Duration, Timer};
    ///
    /// #[embassy_executor::task]
    /// async fn demo_sleep_seconds() {
    ///     // suspend this task for one second.
    ///     Timer::after(Duration::from_secs(1)).await;
    /// }
    /// ```
    pub fn after(duration: Duration) -> Self {
        Self {
            expires_at: Instant::now() + duration,
            yielded_once: false,
        }
    }

    /// Expire after the specified number of ticks.
    ///
    /// This method is a convenience wrapper for calling `Timer::after(Duration::from_ticks())`.
    /// For more details, refer to [`Timer::after()`] and [`Duration::from_ticks()`].
    #[inline]
    pub fn after_ticks(ticks: u64) -> Self {
        Self::after(Duration::from_ticks(ticks))
    }

    /// Expire after the specified number of nanoseconds.
    ///
    /// This method is a convenience wrapper for calling `Timer::after(Duration::from_nanos())`.
    /// For more details, refer to [`Timer::after()`] and [`Duration::from_nanos()`].
    #[inline]
    pub fn after_nanos(nanos: u64) -> Self {
        Self::after(Duration::from_nanos(nanos))
    }

    /// Expire after the specified number of microseconds.
    ///
    /// This method is a convenience wrapper for calling `Timer::after(Duration::from_micros())`.
    /// For more details, refer to [`Timer::after()`] and [`Duration::from_micros()`].
    #[inline]
    pub fn after_micros(micros: u64) -> Self {
        Self::after(Duration::from_micros(micros))
    }

    /// Expire after the specified number of milliseconds.
    ///
    /// This method is a convenience wrapper for calling `Timer::after(Duration::from_millis())`.
    /// For more details, refer to [`Timer::after`] and [`Duration::from_millis()`].
    #[inline]
    pub fn after_millis(millis: u64) -> Self {
        Self::after(Duration::from_millis(millis))
    }

    /// Expire after the specified number of seconds.
    ///
    /// This method is a convenience wrapper for calling `Timer::after(Duration::from_secs())`.
    /// For more details, refer to [`Timer::after`] and [`Duration::from_secs()`].
    #[inline]
    pub fn after_secs(secs: u64) -> Self {
        Self::after(Duration::from_secs(secs))
    }
}

impl Unpin for Timer {}

impl Future for Timer {
    type Output = ();
    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        if self.yielded_once && self.expires_at <= Instant::now() {
            Poll::Ready(())
        } else {
            embassy_time_queue_driver::schedule_wake(self.expires_at.as_ticks(), cx.waker());
            self.yielded_once = true;
            Poll::Pending
        }
    }
}

/// Asynchronous stream that yields every Duration, indefinitely.
///
/// This stream will tick at uniform intervals, even if blocking work is performed between ticks.
///
/// For instance, consider the following code fragment.
/// ``` no_run
/// use embassy_time::{Duration, Timer};
/// # fn foo() {}
///
/// #[embassy_executor::task]
/// async fn ticker_example_0() {
///     loop {
///         foo();
///         Timer::after(Duration::from_secs(1)).await;
///     }
/// }
/// ```
///
/// This fragment will not call `foo` every second.
/// Instead, it will call it every second + the time it took to previously call `foo`.
///
/// Example using ticker, which will consistently call `foo` once a second.
///
/// ``` no_run
/// use embassy_time::{Duration, Ticker};
/// # fn foo(){}
///
/// #[embassy_executor::task]
/// async fn ticker_example_1() {
///     let mut ticker = Ticker::every(Duration::from_secs(1));
///     loop {
///         foo();
///         ticker.next().await;
///     }
/// }
/// ```
pub struct Ticker {
    expires_at: Instant,
    duration: Duration,
}

impl Ticker {
    /// Creates a new ticker that ticks at the specified duration interval.
    pub fn every(duration: Duration) -> Self {
        let expires_at = Instant::now() + duration;
        Self { expires_at, duration }
    }

    /// Resets the ticker back to its original state.
    /// This causes the ticker to go back to zero, even if the current tick isn't over yet.
    pub fn reset(&mut self) {
        self.expires_at = Instant::now() + self.duration;
    }

    /// Waits for the next tick.
    pub fn next(&mut self) -> impl Future<Output = ()> + '_ {
        poll_fn(|cx| {
            if self.expires_at <= Instant::now() {
                let dur = self.duration;
                self.expires_at += dur;
                Poll::Ready(())
            } else {
                embassy_time_queue_driver::schedule_wake(self.expires_at.as_ticks(), cx.waker());
                Poll::Pending
            }
        })
    }
}

impl Unpin for Ticker {}

impl Stream for Ticker {
    type Item = ();
    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        if self.expires_at <= Instant::now() {
            let dur = self.duration;
            self.expires_at += dur;
            Poll::Ready(Some(()))
        } else {
            embassy_time_queue_driver::schedule_wake(self.expires_at.as_ticks(), cx.waker());
            Poll::Pending
        }
    }
}

impl FusedStream for Ticker {
    fn is_terminated(&self) -> bool {
        // `Ticker` keeps yielding values until dropped, it never terminates.
        false
    }
}