axstd/
time.rs

1//! Temporal quantification.
2
3use arceos_api::time::AxTimeValue;
4use core::ops::{Add, AddAssign, Sub, SubAssign};
5
6pub use core::time::Duration;
7
8/// A measurement of a monotonically nondecreasing clock.
9/// Opaque and useful only with [`Duration`].
10#[derive(Clone, Copy)]
11pub struct Instant(AxTimeValue);
12
13impl Instant {
14    /// Returns an instant corresponding to "now".
15    pub fn now() -> Instant {
16        Instant(arceos_api::time::ax_wall_time())
17    }
18
19    /// Returns the amount of time elapsed from another instant to this one,
20    /// or zero duration if that instant is later than this one.
21    ///
22    /// # Panics
23    ///
24    /// Previous rust versions panicked when `earlier` was later than `self`. Currently this
25    /// method saturates. Future versions may reintroduce the panic in some circumstances.
26    pub fn duration_since(&self, earlier: Instant) -> Duration {
27        self.0.checked_sub(earlier.0).unwrap_or_default()
28    }
29
30    /// Returns the amount of time elapsed since this instant was created.
31    ///
32    /// # Panics
33    ///
34    /// Previous rust versions panicked when the current time was earlier than self. Currently this
35    /// method returns a Duration of zero in that case. Future versions may reintroduce the panic.
36    pub fn elapsed(&self) -> Duration {
37        Instant::now() - *self
38    }
39
40    /// Returns `Some(t)` where `t` is the time `self + duration` if `t` can be represented as
41    /// `Instant` (which means it's inside the bounds of the underlying data structure), `None`
42    /// otherwise.
43    pub fn checked_add(&self, duration: Duration) -> Option<Instant> {
44        self.0.checked_add(duration).map(Instant)
45    }
46
47    /// Returns `Some(t)` where `t` is the time `self - duration` if `t` can be represented as
48    /// `Instant` (which means it's inside the bounds of the underlying data structure), `None`
49    /// otherwise.
50    pub fn checked_sub(&self, duration: Duration) -> Option<Instant> {
51        self.0.checked_sub(duration).map(Instant)
52    }
53}
54
55impl Add<Duration> for Instant {
56    type Output = Instant;
57
58    /// # Panics
59    ///
60    /// This function may panic if the resulting point in time cannot be represented by the
61    /// underlying data structure.
62    fn add(self, other: Duration) -> Instant {
63        self.checked_add(other)
64            .expect("overflow when adding duration to instant")
65    }
66}
67
68impl AddAssign<Duration> for Instant {
69    fn add_assign(&mut self, other: Duration) {
70        *self = *self + other;
71    }
72}
73
74impl Sub<Duration> for Instant {
75    type Output = Instant;
76
77    fn sub(self, other: Duration) -> Instant {
78        self.checked_sub(other)
79            .expect("overflow when subtracting duration from instant")
80    }
81}
82
83impl SubAssign<Duration> for Instant {
84    fn sub_assign(&mut self, other: Duration) {
85        *self = *self - other;
86    }
87}
88
89impl Sub<Instant> for Instant {
90    type Output = Duration;
91
92    /// Returns the amount of time elapsed from another instant to this one,
93    /// or zero duration if that instant is later than this one.
94    fn sub(self, other: Instant) -> Duration {
95        self.duration_since(other)
96    }
97}
axstd/time.rs

axstd/
time.rs
