      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
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279
    280
    281
    282
    283
    284
    285
    286
    287
    288
    289
    290
    291
    292
    293
    294
    295
    296
    297
    298
    299
    300
    301
    302
    303
    304
    305
    306
    307
    308
    309
    310
    311
    312
    313
    314
    315
    316
    317
    318
    319
    320
    321
    322
    323
    324
    325
    326
    327
    328
    329
    330
    331
    332
    333
    334
    335
    336
    337
    338
    339
    340
    341
    342
    343
    344
    345
    346
    347
    348
    349
    350
    351
    352
    353
    354
    355
    356
    357
    358
    359
    360
    361
    362
    363
    364
    365
    366
    367
    368
    369
    370
    371
    372
    373
    374
    375
    376
    377
    378
    379
    380
    381
    382
    383
    384
    385
    386
    387
    388
    389
    390
    391
    392
    393
    394
    395
    396
    397
    398
    399
    400
    401
    402
    403
    404
    405
    406
    407
    408
    409
    410
    411
    412
    413
    414
    415
    416
    417
    418
    419
    420
    421
    422
    423
    424
    425
    426
    427
    428
    429
    430
    431
    432
    433
    434
    435
    436
    437
    438
    439
    440
    441
    442
    443
    444
    445
    446
    447
    448
    449
    450

    // 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 self::duration::Duration;

    mod duration;

    /// A measurement of a monotonically increasing clock.
    ///  Opaque and useful only with `Duration`.
    ///
    /// Instants are always guaranteed to be greater 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)]
    #[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 second**. 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.
    ///
    /// 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 occured!
    ///            println!("Error: {:?}", e);
    ///        }
    ///    }
    /// }
    /// ```
    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
    #[stable(feature = "time2", since = "1.8.0")]
    pub struct SystemTime(time::SystemTime);

    /// An error returned from the `duration_since` method on `SystemTime`,
    /// used to learn about why how far in the opposite direction a timestamp lies.
    #[derive(Clone, Debug)]
    #[stable(feature = "time2", since = "1.8.0")]
    pub struct SystemTimeError(Duration);

    impl Instant {
        /// Returns an instant corresponding to "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`, which should
        /// only be possible if `earlier` was created after `self`. Because
        /// `Instant` is monotonic, the only time that this should happen should be
        /// a bug.
        #[stable(feature = "time2", since = "1.8.0")]
        pub fn duration_since(&self, earlier: Instant) -> Duration {
            self.0.sub_instant(&earlier.0)
        }

        /// Deprecated, renamed to `duration_since`
        #[unstable(feature = "time2_old", issue = "29866")]
        #[rustc_deprecated(since = "1.8.0", reason = "renamed to duration_since")]
        pub fn duration_from_earlier(&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.
        #[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".
        #[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.
        #[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)
        }

        /// Deprecated, renamed to `duration_since`
        #[unstable(feature = "time2_old", issue = "29866")]
        #[rustc_deprecated(since = "1.8.0", reason = "renamed to duration_since")]
        pub fn duration_from_earlier(&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.
        #[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.
    #[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`
        /// operation whenever the second system time represents a point later
        /// in time than the `self` of the method call.
        #[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!(b - dur, a);
                }
            }

            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);

            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's assume that we're all running computers later than 2000
            let thirty_years = Duration::new(1, 0) * 60 * 60 * 24 * 365 * 30;
            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);
        }
    }

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)