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

/* This file is part of DarkFi (https://dark.fi)
 *
 * Copyright (C) 2020-2024 Dyne.org foundation
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

use std::{
    error::Error,
    fmt,
    future::Future,
    io,
    pin::Pin,
    task::{Context, Poll},
    time::Duration,
};

use pin_project_lite::pin_project;
use smol::Timer;

/// Awaits an I/O future or times out after a duration of time.
///
/// If you want to await a non I/O future consider using
/// `timeout()` instead.
///
/// # Examples
///
/// ```no_run
/// # fn main() -> std::io::Result<()> { smol::block_on(async {
/// #
/// use std::time::Duration;
/// use std::io;
///
/// io_timeout(Duration::from_secs(5), async {
///     let stdin = io::stdin();
///     let mut line = String::new();
///     let n = stdin.read_line(&mut line)?;
///     Ok(())
/// })
/// .await?;
/// #
/// # Ok(()) }) }
pub async fn io_timeout<F, T>(dur: Duration, f: F) -> io::Result<T>
where
    F: Future<Output = io::Result<T>>,
{
    Timeout { timeout: Timer::after(dur), future: f }.await
}

pin_project! {
    #[derive(Debug)]
    pub struct Timeout<F, T>
    where
        F: Future<Output = io::Result<T>>,
    {
        #[pin]
        future: F,
        #[pin]
        timeout: Timer,
    }
}

impl<F, T> Future for Timeout<F, T>
where
    F: Future<Output = io::Result<T>>,
{
    type Output = io::Result<T>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let this = self.project();
        match this.future.poll(cx) {
            Poll::Pending => {}
            other => return other,
        }

        if this.timeout.poll(cx).is_ready() {
            let err = Err(io::Error::new(io::ErrorKind::TimedOut, "future timed out"));
            Poll::Ready(err)
        } else {
            Poll::Pending
        }
    }
}

/// Awaits a future or times out after a duration of time.
///
/// If you want to await an I/O future consider using
/// `io_timeout` instead.
///
/// # Examples
///
/// ```
/// # fn main() -> std::io::Result<()> { smol::block_on(async {
/// #
/// use std::time::Duration;
/// use smol::future;
///
/// let never = future::pending::<()>();
/// let dur = Duration::from_millis(5);
/// assert!(timeout(dur, never).await.is_err());
/// #
/// # Ok(()) }) }
/// ```
pub async fn timeout<F, T>(dur: Duration, f: F) -> Result<T, TimeoutError>
where
    F: Future<Output = T>,
{
    TimeoutFuture::new(f, dur).await
}

pin_project! {
    /// A future that times out after a duration of time.
    pub struct TimeoutFuture<F> {
        #[pin]
        future: F,
        #[pin]
        delay: Timer,
    }
}

impl<F> TimeoutFuture<F> {
    #[allow(dead_code)]
    pub(super) fn new(future: F, dur: Duration) -> TimeoutFuture<F> {
        TimeoutFuture { future, delay: Timer::after(dur) }
    }
}

impl<F: Future> Future for TimeoutFuture<F> {
    type Output = Result<F::Output, TimeoutError>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let this = self.project();
        match this.future.poll(cx) {
            Poll::Ready(v) => Poll::Ready(Ok(v)),
            Poll::Pending => match this.delay.poll(cx) {
                Poll::Ready(_) => Poll::Ready(Err(TimeoutError { _private: () })),
                Poll::Pending => Poll::Pending,
            },
        }
    }
}

/// An error returned when a future times out.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct TimeoutError {
    _private: (),
}

impl Error for TimeoutError {}

impl fmt::Display for TimeoutError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        "future has timed out".fmt(f)
    }
}