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use libc::{c_long, clock_gettime, clockid_t, timespec};
use std::{mem::MaybeUninit, time::Duration};
const NSEC_PER_SEC: c_long = 1_000_000_000;
#[cfg(target_os = "macos")]
const CLOCK_ID: clockid_t = libc::CLOCK_MONOTONIC;
#[cfg(any(target_os = "linux", target_os = "android"))]
const CLOCK_ID: clockid_t = libc::CLOCK_BOOTTIME;
#[derive(Clone, Copy)]
pub struct Instant {
t: timespec,
}
impl Instant {
pub fn now() -> Self {
Self { t: now() }
}
fn checked_duration_since(&self, earlier: Instant) -> Option<Duration> {
// Assumptions:
// * `tv_sec >= 0`
// * `tv_nsec < NSEC_PER_SEC`
let (tv_sec, tv_nsec) = if self.t.tv_nsec < earlier.t.tv_nsec {
(
self.t.tv_sec - earlier.t.tv_sec - 1,
NSEC_PER_SEC - earlier.t.tv_nsec + self.t.tv_nsec,
)
} else {
(
self.t.tv_sec - earlier.t.tv_sec,
self.t.tv_nsec - earlier.t.tv_nsec,
)
};
if tv_sec < 0 {
return None;
}
Some(Duration::new(tv_sec as _, tv_nsec as _))
}
pub fn duration_since(&self, earlier: Instant) -> Duration {
self.checked_duration_since(earlier)
.unwrap_or(Duration::ZERO)
}
}
fn now() -> timespec {
let mut t = MaybeUninit::zeroed();
unsafe {
clock_gettime(CLOCK_ID, t.as_mut_ptr());
t.assume_init()
}
}
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