sgx_tstd/src/untrusted/time.rs

// Copyright (C) 2017-2018 Baidu, Inc. All Rights Reserved.
//
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use core::mem;
use sys::time;
use time::{Instant, SystemTime, SystemTimeError, Duration};

pub trait InstantEx {
    fn now() -> Instant;
    fn elapsed(&self) -> Duration;
}

impl InstantEx for Instant {
    /// Returns an instant corresponding to "now".
    ///
    fn now() -> Instant {
        let instant = inner::Instant(time::Instant::now());
        unsafe { mem::transmute(instant) }
    }

    /// Returns the amount of time elapsed since this instant was created.
    ///
    /// # Panics
    ///
    /// This function may panic if the current time is earlier than this
    /// instant, which is something that can happen if an `Instant` is
    /// produced synthetically.
    ///
    fn elapsed(&self) -> Duration {
        Instant::now() - *self
    }
}

pub trait SystemTimeEx {
    fn now() -> SystemTime;
    fn elapsed(&self) -> Result<Duration, SystemTimeError>;
}

impl SystemTimeEx for SystemTime {
    /// Returns the system time corresponding to "now".
    ///
    fn now() -> SystemTime {
        let systemtime = inner::SystemTime(time::SystemTime::now());
        unsafe { mem::transmute(systemtime) }
    }

    /// Returns the amount of time elapsed since this system time was created.
    ///
    /// This function may fail as the underlying system clock is susceptible to
    /// drift and updates (e.g. the system clock could go backwards), so this
    /// function may not always succeed. If successful, [`Ok`]`(`[`Duration`]`)` is
    /// returned where the duration represents the amount of time elapsed from
    /// this time measurement to the current time.
    ///
    /// Returns an [`Err`] if `self` is later than the current system time, and
    /// the error contains how far from the current system time `self` is.
    ///
    fn elapsed(&self) -> Result<Duration, SystemTimeError> {
        SystemTime::now().duration_since(*self)
    }
}

mod inner {
    use sys::time;
    pub struct Instant(pub time::Instant);
    pub struct SystemTime(pub time::SystemTime);
}