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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. //! Temporal quantification. //! //! Example: //! //! ``` //! use std::time::Duration; //! //! let five_seconds = Duration::new(5, 0); //! // both declarations are equivalent //! assert_eq!(Duration::new(5, 0), Duration::from_secs(5)); //! ``` #![stable(feature = "time", since = "1.3.0")] use error::Error; use fmt; use ops::{Add, Sub, AddAssign, SubAssign}; use sys::time; use sys_common::FromInner; #[stable(feature = "time", since = "1.3.0")] pub use core::time::Duration; /// A measurement of a monotonically nondecreasing clock. /// Opaque and useful only with `Duration`. /// /// Instants are always guaranteed to be no less than any previously measured /// instant when created, and are often useful for tasks such as measuring /// benchmarks or timing how long an operation takes. /// /// Note, however, that instants are not guaranteed to be **steady**. In other /// words, each tick of the underlying clock may not be the same length (e.g. /// some seconds may be longer than others). An instant may jump forwards or /// experience time dilation (slow down or speed up), but it will never go /// backwards. /// /// Instants are opaque types that can only be compared to one another. There is /// no method to get "the number of seconds" from an instant. Instead, it only /// allows measuring the duration between two instants (or comparing two /// instants). /// /// Example: /// /// ```no_run /// use std::time::{Duration, Instant}; /// use std::thread::sleep; /// /// fn main() { /// let now = Instant::now(); /// /// // we sleep for 2 seconds /// sleep(Duration::new(2, 0)); /// // it prints '2' /// println!("{}", now.elapsed().as_secs()); /// } /// ``` #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] #[stable(feature = "time2", since = "1.8.0")] pub struct Instant(time::Instant); /// A measurement of the system clock, useful for talking to /// external entities like the file system or other processes. /// /// Distinct from the [`Instant`] type, this time measurement **is not /// monotonic**. This means that you can save a file to the file system, then /// save another file to the file system, **and the second file has a /// `SystemTime` measurement earlier than the first**. In other words, an /// operation that happens after another operation in real time may have an /// earlier `SystemTime`! /// /// Consequently, comparing two `SystemTime` instances to learn about the /// duration between them returns a [`Result`] instead of an infallible [`Duration`] /// to indicate that this sort of time drift may happen and needs to be handled. /// /// Although a `SystemTime` cannot be directly inspected, the [`UNIX_EPOCH`] /// constant is provided in this module as an anchor in time to learn /// information about a `SystemTime`. By calculating the duration from this /// fixed point in time, a `SystemTime` can be converted to a human-readable time, /// or perhaps some other string representation. /// /// [`Instant`]: ../../std/time/struct.Instant.html /// [`Result`]: ../../std/result/enum.Result.html /// [`Duration`]: ../../std/time/struct.Duration.html /// [`UNIX_EPOCH`]: ../../std/time/constant.UNIX_EPOCH.html /// /// Example: /// /// ```no_run /// use std::time::{Duration, SystemTime}; /// use std::thread::sleep; /// /// fn main() { /// let now = SystemTime::now(); /// /// // we sleep for 2 seconds /// sleep(Duration::new(2, 0)); /// match now.elapsed() { /// Ok(elapsed) => { /// // it prints '2' /// println!("{}", elapsed.as_secs()); /// } /// Err(e) => { /// // an error occurred! /// println!("Error: {:?}", e); /// } /// } /// } /// ``` #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] #[stable(feature = "time2", since = "1.8.0")] pub struct SystemTime(time::SystemTime); /// An error returned from the `duration_since` and `elapsed` methods on /// `SystemTime`, used to learn how far in the opposite direction a system time /// lies. /// /// # Examples /// /// ```no_run /// use std::thread::sleep; /// use std::time::{Duration, SystemTime}; /// /// let sys_time = SystemTime::now(); /// sleep(Duration::from_secs(1)); /// let new_sys_time = SystemTime::now(); /// match sys_time.duration_since(new_sys_time) { /// Ok(_) => {} /// Err(e) => println!("SystemTimeError difference: {:?}", e.duration()), /// } /// ``` #[derive(Clone, Debug)] #[stable(feature = "time2", since = "1.8.0")] pub struct SystemTimeError(Duration); impl Instant { /// Returns an instant corresponding to "now". /// /// # Examples /// /// ``` /// use std::time::Instant; /// /// let now = Instant::now(); /// ``` #[stable(feature = "time2", since = "1.8.0")] pub fn now() -> Instant { Instant(time::Instant::now()) } /// Returns the amount of time elapsed from another instant to this one. /// /// # Panics /// /// This function will panic if `earlier` is later than `self`. /// /// # Examples /// /// ```no_run /// use std::time::{Duration, Instant}; /// use std::thread::sleep; /// /// let now = Instant::now(); /// sleep(Duration::new(1, 0)); /// let new_now = Instant::now(); /// println!("{:?}", new_now.duration_since(now)); /// ``` #[stable(feature = "time2", since = "1.8.0")] pub fn duration_since(&self, earlier: Instant) -> Duration { self.0.sub_instant(&earlier.0) } /// 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. /// /// # Examples /// /// ```no_run /// use std::thread::sleep; /// use std::time::{Duration, Instant}; /// /// let instant = Instant::now(); /// let three_secs = Duration::from_secs(3); /// sleep(three_secs); /// assert!(instant.elapsed() >= three_secs); /// ``` #[stable(feature = "time2", since = "1.8.0")] pub fn elapsed(&self) -> Duration { Instant::now() - *self } } #[stable(feature = "time2", since = "1.8.0")] impl Add<Duration> for Instant { type Output = Instant; fn add(self, other: Duration) -> Instant { Instant(self.0.add_duration(&other)) } } #[stable(feature = "time_augmented_assignment", since = "1.9.0")] impl AddAssign<Duration> for Instant { fn add_assign(&mut self, other: Duration) { *self = *self + other; } } #[stable(feature = "time2", since = "1.8.0")] impl Sub<Duration> for Instant { type Output = Instant; fn sub(self, other: Duration) -> Instant { Instant(self.0.sub_duration(&other)) } } #[stable(feature = "time_augmented_assignment", since = "1.9.0")] impl SubAssign<Duration> for Instant { fn sub_assign(&mut self, other: Duration) { *self = *self - other; } } #[stable(feature = "time2", since = "1.8.0")] impl Sub<Instant> for Instant { type Output = Duration; fn sub(self, other: Instant) -> Duration { self.duration_since(other) } } #[stable(feature = "time2", since = "1.8.0")] impl fmt::Debug for Instant { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { self.0.fmt(f) } } impl SystemTime { /// Returns the system time corresponding to "now". /// /// # Examples /// /// ``` /// use std::time::SystemTime; /// /// let sys_time = SystemTime::now(); /// ``` #[stable(feature = "time2", since = "1.8.0")] pub fn now() -> SystemTime { SystemTime(time::SystemTime::now()) } /// Returns the amount of time elapsed from an earlier point in time. /// /// This function may fail because measurements taken earlier are not /// guaranteed to always be before later measurements (due to anomalies such /// as the system clock being adjusted either forwards or backwards). /// /// If successful, [`Ok`]`(`[`Duration`]`)` is returned where the duration represents /// the amount of time elapsed from the specified measurement to this one. /// /// Returns an [`Err`] if `earlier` is later than `self`, and the error /// contains how far from `self` the time is. /// /// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok /// [`Duration`]: ../../std/time/struct.Duration.html /// [`Err`]: ../../std/result/enum.Result.html#variant.Err /// /// # Examples /// /// ``` /// use std::time::SystemTime; /// /// let sys_time = SystemTime::now(); /// let difference = sys_time.duration_since(sys_time) /// .expect("SystemTime::duration_since failed"); /// println!("{:?}", difference); /// ``` #[stable(feature = "time2", since = "1.8.0")] pub fn duration_since(&self, earlier: SystemTime) -> Result<Duration, SystemTimeError> { self.0.sub_time(&earlier.0).map_err(SystemTimeError) } /// 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. /// /// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok /// [`Duration`]: ../../std/time/struct.Duration.html /// [`Err`]: ../../std/result/enum.Result.html#variant.Err /// /// # Examples /// /// ```no_run /// use std::thread::sleep; /// use std::time::{Duration, SystemTime}; /// /// let sys_time = SystemTime::now(); /// let one_sec = Duration::from_secs(1); /// sleep(one_sec); /// assert!(sys_time.elapsed().unwrap() >= one_sec); /// ``` #[stable(feature = "time2", since = "1.8.0")] pub fn elapsed(&self) -> Result<Duration, SystemTimeError> { SystemTime::now().duration_since(*self) } } #[stable(feature = "time2", since = "1.8.0")] impl Add<Duration> for SystemTime { type Output = SystemTime; fn add(self, dur: Duration) -> SystemTime { SystemTime(self.0.add_duration(&dur)) } } #[stable(feature = "time_augmented_assignment", since = "1.9.0")] impl AddAssign<Duration> for SystemTime { fn add_assign(&mut self, other: Duration) { *self = *self + other; } } #[stable(feature = "time2", since = "1.8.0")] impl Sub<Duration> for SystemTime { type Output = SystemTime; fn sub(self, dur: Duration) -> SystemTime { SystemTime(self.0.sub_duration(&dur)) } } #[stable(feature = "time_augmented_assignment", since = "1.9.0")] impl SubAssign<Duration> for SystemTime { fn sub_assign(&mut self, other: Duration) { *self = *self - other; } } #[stable(feature = "time2", since = "1.8.0")] impl fmt::Debug for SystemTime { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { self.0.fmt(f) } } /// An anchor in time which can be used to create new `SystemTime` instances or /// learn about where in time a `SystemTime` lies. /// /// This constant is defined to be "1970-01-01 00:00:00 UTC" on all systems with /// respect to the system clock. Using `duration_since` on an existing /// [`SystemTime`] instance can tell how far away from this point in time a /// measurement lies, and using `UNIX_EPOCH + duration` can be used to create a /// [`SystemTime`] instance to represent another fixed point in time. /// /// [`SystemTime`]: ../../std/time/struct.SystemTime.html /// /// # Examples /// /// ```no_run /// use std::time::{SystemTime, UNIX_EPOCH}; /// /// match SystemTime::now().duration_since(UNIX_EPOCH) { /// Ok(n) => println!("1970-01-01 00:00:00 UTC was {} seconds ago!", n.as_secs()), /// Err(_) => panic!("SystemTime before UNIX EPOCH!"), /// } /// ``` #[stable(feature = "time2", since = "1.8.0")] pub const UNIX_EPOCH: SystemTime = SystemTime(time::UNIX_EPOCH); impl SystemTimeError { /// Returns the positive duration which represents how far forward the /// second system time was from the first. /// /// A `SystemTimeError` is returned from the [`duration_since`] and [`elapsed`] /// methods of [`SystemTime`] whenever the second system time represents a point later /// in time than the `self` of the method call. /// /// [`duration_since`]: ../../std/time/struct.SystemTime.html#method.duration_since /// [`elapsed`]: ../../std/time/struct.SystemTime.html#method.elapsed /// [`SystemTime`]: ../../std/time/struct.SystemTime.html /// /// # Examples /// /// ```no_run /// use std::thread::sleep; /// use std::time::{Duration, SystemTime}; /// /// let sys_time = SystemTime::now(); /// sleep(Duration::from_secs(1)); /// let new_sys_time = SystemTime::now(); /// match sys_time.duration_since(new_sys_time) { /// Ok(_) => {} /// Err(e) => println!("SystemTimeError difference: {:?}", e.duration()), /// } /// ``` #[stable(feature = "time2", since = "1.8.0")] pub fn duration(&self) -> Duration { self.0 } } #[stable(feature = "time2", since = "1.8.0")] impl Error for SystemTimeError { fn description(&self) -> &str { "other time was not earlier than self" } } #[stable(feature = "time2", since = "1.8.0")] impl fmt::Display for SystemTimeError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "second time provided was later than self") } } impl FromInner<time::SystemTime> for SystemTime { fn from_inner(time: time::SystemTime) -> SystemTime { SystemTime(time) } } #[cfg(test)] mod tests { use super::{Instant, SystemTime, Duration, UNIX_EPOCH}; macro_rules! assert_almost_eq { ($a:expr, $b:expr) => ({ let (a, b) = ($a, $b); if a != b { let (a, b) = if a > b {(a, b)} else {(b, a)}; assert!(a - Duration::new(0, 100) <= b); } }) } #[test] fn instant_monotonic() { let a = Instant::now(); let b = Instant::now(); assert!(b >= a); } #[test] fn instant_elapsed() { let a = Instant::now(); a.elapsed(); } #[test] fn instant_math() { let a = Instant::now(); let b = Instant::now(); let dur = b.duration_since(a); assert_almost_eq!(b - dur, a); assert_almost_eq!(a + dur, b); let second = Duration::new(1, 0); assert_almost_eq!(a - second + second, a); } #[test] #[should_panic] fn instant_duration_panic() { let a = Instant::now(); (a - Duration::new(1, 0)).duration_since(a); } #[test] fn system_time_math() { let a = SystemTime::now(); let b = SystemTime::now(); match b.duration_since(a) { Ok(dur) if dur == Duration::new(0, 0) => { assert_almost_eq!(a, b); } Ok(dur) => { assert!(b > a); assert_almost_eq!(b - dur, a); assert_almost_eq!(a + dur, b); } Err(dur) => { let dur = dur.duration(); assert!(a > b); assert_almost_eq!(b + dur, a); assert_almost_eq!(a - dur, b); } } let second = Duration::new(1, 0); assert_almost_eq!(a.duration_since(a - second).unwrap(), second); assert_almost_eq!(a.duration_since(a + second).unwrap_err() .duration(), second); assert_almost_eq!(a - second + second, a); // A difference of 80 and 800 years cannot fit inside a 32-bit time_t if !(cfg!(unix) && ::mem::size_of::<::libc::time_t>() <= 4) { let eighty_years = second * 60 * 60 * 24 * 365 * 80; assert_almost_eq!(a - eighty_years + eighty_years, a); assert_almost_eq!(a - (eighty_years * 10) + (eighty_years * 10), a); } let one_second_from_epoch = UNIX_EPOCH + Duration::new(1, 0); let one_second_from_epoch2 = UNIX_EPOCH + Duration::new(0, 500_000_000) + Duration::new(0, 500_000_000); assert_eq!(one_second_from_epoch, one_second_from_epoch2); } #[test] fn system_time_elapsed() { let a = SystemTime::now(); drop(a.elapsed()); } #[test] fn since_epoch() { let ts = SystemTime::now(); let a = ts.duration_since(UNIX_EPOCH).unwrap(); let b = ts.duration_since(UNIX_EPOCH - Duration::new(1, 0)).unwrap(); assert!(b > a); assert_eq!(b - a, Duration::new(1, 0)); let thirty_years = Duration::new(1, 0) * 60 * 60 * 24 * 365 * 30; // Right now for CI this test is run in an emulator, and apparently the // aarch64 emulator's sense of time is that we're still living in the // 70s. // // Otherwise let's assume that we're all running computers later than // 2000. if !cfg!(target_arch = "aarch64") { assert!(a > thirty_years); } // let's assume that we're all running computers earlier than 2090. // Should give us ~70 years to fix this! let hundred_twenty_years = thirty_years * 4; assert!(a < hundred_twenty_years); } }