library/core/src/time.rs

   1 #![stable(feature = "duration_core", since = "1.25.0")]
   2
   3 //! Temporal quantification.
   4 //!
   5 //! Example:
   6 //!
   7 //! ```
   8 //! use std::time::Duration;
   9 //!
  10 //! let five_seconds = Duration::new(5, 0);
  11 //! // both declarations are equivalent
  12 //! assert_eq!(Duration::new(5, 0), Duration::from_secs(5));
  13 //! ```
  14
  15 use crate::fmt;
  16 use crate::iter::Sum;
  17 use crate::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
  18
  19 const NANOS_PER_SEC: u32 = 1_000_000_000;
  20 const NANOS_PER_MILLI: u32 = 1_000_000;
  21 const NANOS_PER_MICRO: u32 = 1_000;
  22 const MILLIS_PER_SEC: u64 = 1_000;
  23 const MICROS_PER_SEC: u64 = 1_000_000;
  24
  25 /// A `Duration` type to represent a span of time, typically used for system
  26 /// timeouts.
  27 ///
  28 /// Each `Duration` is composed of a whole number of seconds and a fractional part
  29 /// represented in nanoseconds. If the underlying system does not support
  30 /// nanosecond-level precision, APIs binding a system timeout will typically round up
  31 /// the number of nanoseconds.
  32 ///
  33 /// [`Duration`]s implement many common traits, including [`Add`], [`Sub`], and other
  34 /// [`ops`] traits. It implements [`Default`] by returning a zero-length `Duration`.
  35 ///
  36 /// [`ops`]: crate::ops
  37 ///
  38 /// # Examples
  39 ///
  40 /// ```
  41 /// use std::time::Duration;
  42 ///
  43 /// let five_seconds = Duration::new(5, 0);
  44 /// let five_seconds_and_five_nanos = five_seconds + Duration::new(0, 5);
  45 ///
  46 /// assert_eq!(five_seconds_and_five_nanos.as_secs(), 5);
  47 /// assert_eq!(five_seconds_and_five_nanos.subsec_nanos(), 5);
  48 ///
  49 /// let ten_millis = Duration::from_millis(10);
  50 /// ```
  51 #[stable(feature = "duration", since = "1.3.0")]
  52 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
  53 pub struct Duration {
  54     secs: u64,
  55     nanos: u32, // Always 0 <= nanos < NANOS_PER_SEC
  56 }
  57
  58 impl Duration {
  59     /// The duration of one second.
  60     ///
  61     /// # Examples
  62     ///
  63     /// ```
  64     /// #![feature(duration_constants)]
  65     /// use std::time::Duration;
  66     ///
  67     /// assert_eq!(Duration::SECOND, Duration::from_secs(1));
  68     /// ```
  69     #[unstable(feature = "duration_constants", issue = "57391")]
  70     pub const SECOND: Duration = Duration::from_secs(1);
  71
  72     /// The duration of one millisecond.
  73     ///
  74     /// # Examples
  75     ///
  76     /// ```
  77     /// #![feature(duration_constants)]
  78     /// use std::time::Duration;
  79     ///
  80     /// assert_eq!(Duration::MILLISECOND, Duration::from_millis(1));
  81     /// ```
  82     #[unstable(feature = "duration_constants", issue = "57391")]
  83     pub const MILLISECOND: Duration = Duration::from_millis(1);
  84
  85     /// The duration of one microsecond.
  86     ///
  87     /// # Examples
  88     ///
  89     /// ```
  90     /// #![feature(duration_constants)]
  91     /// use std::time::Duration;
  92     ///
  93     /// assert_eq!(Duration::MICROSECOND, Duration::from_micros(1));
  94     /// ```
  95     #[unstable(feature = "duration_constants", issue = "57391")]
  96     pub const MICROSECOND: Duration = Duration::from_micros(1);
  97
  98     /// The duration of one nanosecond.
  99     ///
 100     /// # Examples
 101     ///
 102     /// ```
 103     /// #![feature(duration_constants)]
 104     /// use std::time::Duration;
 105     ///
 106     /// assert_eq!(Duration::NANOSECOND, Duration::from_nanos(1));
 107     /// ```
 108     #[unstable(feature = "duration_constants", issue = "57391")]
 109     pub const NANOSECOND: Duration = Duration::from_nanos(1);
 110
 111     /// The minimum duration.
 112     ///
 113     /// # Examples
 114     ///
 115     /// ```
 116     /// #![feature(duration_constants)]
 117     /// use std::time::Duration;
 118     ///
 119     /// assert_eq!(Duration::MIN, Duration::new(0, 0));
 120     /// ```
 121     #[unstable(feature = "duration_constants", issue = "57391")]
 122     pub const MIN: Duration = Duration::from_nanos(0);
 123
 124     /// The maximum duration.
 125     ///
 126     /// It is roughly equal to a duration of 584,942,417,355 years.
 127     ///
 128     /// # Examples
 129     ///
 130     /// ```
 131     /// #![feature(duration_constants)]
 132     /// use std::time::Duration;
 133     ///
 134     /// assert_eq!(Duration::MAX, Duration::new(u64::MAX, 1_000_000_000 - 1));
 135     /// ```
 136     #[unstable(feature = "duration_constants", issue = "57391")]
 137     pub const MAX: Duration = Duration::new(u64::MAX, NANOS_PER_SEC - 1);
 138
 139     /// Creates a new `Duration` from the specified number of whole seconds and
 140     /// additional nanoseconds.
 141     ///
 142     /// If the number of nanoseconds is greater than 1 billion (the number of
 143     /// nanoseconds in a second), then it will carry over into the seconds provided.
 144     ///
 145     /// # Panics
 146     ///
 147     /// This constructor will panic if the carry from the nanoseconds overflows
 148     /// the seconds counter.
 149     ///
 150     /// # Examples
 151     ///
 152     /// ```
 153     /// use std::time::Duration;
 154     ///
 155     /// let five_seconds = Duration::new(5, 0);
 156     /// ```
 157     #[stable(feature = "duration", since = "1.3.0")]
 158     #[inline]
 159     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 160     pub const fn new(secs: u64, nanos: u32) -> Duration {
 161         let secs = match secs.checked_add((nanos / NANOS_PER_SEC) as u64) {
 162             Some(secs) => secs,
 163             None => panic!("overflow in Duration::new"),
 164         };
 165         let nanos = nanos % NANOS_PER_SEC;
 166         Duration { secs, nanos }
 167     }
 168
 169     /// Creates a new `Duration` that spans no time.
 170     ///
 171     /// # Examples
 172     ///
 173     /// ```
 174     /// #![feature(duration_zero)]
 175     /// use std::time::Duration;
 176     ///
 177     /// let duration = Duration::zero();
 178     /// assert!(duration.is_zero());
 179     /// assert_eq!(duration.as_nanos(), 0);
 180     /// ```
 181     #[unstable(feature = "duration_zero", issue = "73544")]
 182     #[inline]
 183     pub const fn zero() -> Duration {
 184         Duration { secs: 0, nanos: 0 }
 185     }
 186
 187     /// Creates a new `Duration` from the specified number of whole seconds.
 188     ///
 189     /// # Examples
 190     ///
 191     /// ```
 192     /// use std::time::Duration;
 193     ///
 194     /// let duration = Duration::from_secs(5);
 195     ///
 196     /// assert_eq!(5, duration.as_secs());
 197     /// assert_eq!(0, duration.subsec_nanos());
 198     /// ```
 199     #[stable(feature = "duration", since = "1.3.0")]
 200     #[inline]
 201     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 202     pub const fn from_secs(secs: u64) -> Duration {
 203         Duration { secs, nanos: 0 }
 204     }
 205
 206     /// Creates a new `Duration` from the specified number of milliseconds.
 207     ///
 208     /// # Examples
 209     ///
 210     /// ```
 211     /// use std::time::Duration;
 212     ///
 213     /// let duration = Duration::from_millis(2569);
 214     ///
 215     /// assert_eq!(2, duration.as_secs());
 216     /// assert_eq!(569_000_000, duration.subsec_nanos());
 217     /// ```
 218     #[stable(feature = "duration", since = "1.3.0")]
 219     #[inline]
 220     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 221     pub const fn from_millis(millis: u64) -> Duration {
 222         Duration {
 223             secs: millis / MILLIS_PER_SEC,
 224             nanos: ((millis % MILLIS_PER_SEC) as u32) * NANOS_PER_MILLI,
 225         }
 226     }
 227
 228     /// Creates a new `Duration` from the specified number of microseconds.
 229     ///
 230     /// # Examples
 231     ///
 232     /// ```
 233     /// use std::time::Duration;
 234     ///
 235     /// let duration = Duration::from_micros(1_000_002);
 236     ///
 237     /// assert_eq!(1, duration.as_secs());
 238     /// assert_eq!(2000, duration.subsec_nanos());
 239     /// ```
 240     #[stable(feature = "duration_from_micros", since = "1.27.0")]
 241     #[inline]
 242     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 243     pub const fn from_micros(micros: u64) -> Duration {
 244         Duration {
 245             secs: micros / MICROS_PER_SEC,
 246             nanos: ((micros % MICROS_PER_SEC) as u32) * NANOS_PER_MICRO,
 247         }
 248     }
 249
 250     /// Creates a new `Duration` from the specified number of nanoseconds.
 251     ///
 252     /// # Examples
 253     ///
 254     /// ```
 255     /// use std::time::Duration;
 256     ///
 257     /// let duration = Duration::from_nanos(1_000_000_123);
 258     ///
 259     /// assert_eq!(1, duration.as_secs());
 260     /// assert_eq!(123, duration.subsec_nanos());
 261     /// ```
 262     #[stable(feature = "duration_extras", since = "1.27.0")]
 263     #[inline]
 264     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 265     pub const fn from_nanos(nanos: u64) -> Duration {
 266         Duration {
 267             secs: nanos / (NANOS_PER_SEC as u64),
 268             nanos: (nanos % (NANOS_PER_SEC as u64)) as u32,
 269         }
 270     }
 271
 272     /// Returns true if this `Duration` spans no time.
 273     ///
 274     /// # Examples
 275     ///
 276     /// ```
 277     /// #![feature(duration_zero)]
 278     /// use std::time::Duration;
 279     ///
 280     /// assert!(Duration::zero().is_zero());
 281     /// assert!(Duration::new(0, 0).is_zero());
 282     /// assert!(Duration::from_nanos(0).is_zero());
 283     /// assert!(Duration::from_secs(0).is_zero());
 284     ///
 285     /// assert!(!Duration::new(1, 1).is_zero());
 286     /// assert!(!Duration::from_nanos(1).is_zero());
 287     /// assert!(!Duration::from_secs(1).is_zero());
 288     /// ```
 289     #[unstable(feature = "duration_zero", issue = "73544")]
 290     #[inline]
 291     pub const fn is_zero(&self) -> bool {
 292         self.secs == 0 && self.nanos == 0
 293     }
 294
 295     /// Returns the number of _whole_ seconds contained by this `Duration`.
 296     ///
 297     /// The returned value does not include the fractional (nanosecond) part of the
 298     /// duration, which can be obtained using [`subsec_nanos`].
 299     ///
 300     /// # Examples
 301     ///
 302     /// ```
 303     /// use std::time::Duration;
 304     ///
 305     /// let duration = Duration::new(5, 730023852);
 306     /// assert_eq!(duration.as_secs(), 5);
 307     /// ```
 308     ///
 309     /// To determine the total number of seconds represented by the `Duration`,
 310     /// use `as_secs` in combination with [`subsec_nanos`]:
 311     ///
 312     /// ```
 313     /// use std::time::Duration;
 314     ///
 315     /// let duration = Duration::new(5, 730023852);
 316     ///
 317     /// assert_eq!(5.730023852,
 318     ///            duration.as_secs() as f64
 319     ///            + duration.subsec_nanos() as f64 * 1e-9);
 320     /// ```
 321     ///
 322     /// [`subsec_nanos`]: Duration::subsec_nanos
 323     #[stable(feature = "duration", since = "1.3.0")]
 324     #[rustc_const_stable(feature = "duration", since = "1.32.0")]
 325     #[inline]
 326     pub const fn as_secs(&self) -> u64 {
 327         self.secs
 328     }
 329
 330     /// Returns the fractional part of this `Duration`, in whole milliseconds.
 331     ///
 332     /// This method does **not** return the length of the duration when
 333     /// represented by milliseconds. The returned number always represents a
 334     /// fractional portion of a second (i.e., it is less than one thousand).
 335     ///
 336     /// # Examples
 337     ///
 338     /// ```
 339     /// use std::time::Duration;
 340     ///
 341     /// let duration = Duration::from_millis(5432);
 342     /// assert_eq!(duration.as_secs(), 5);
 343     /// assert_eq!(duration.subsec_millis(), 432);
 344     /// ```
 345     #[stable(feature = "duration_extras", since = "1.27.0")]
 346     #[rustc_const_stable(feature = "duration_extras", since = "1.32.0")]
 347     #[inline]
 348     pub const fn subsec_millis(&self) -> u32 {
 349         self.nanos / NANOS_PER_MILLI
 350     }
 351
 352     /// Returns the fractional part of this `Duration`, in whole microseconds.
 353     ///
 354     /// This method does **not** return the length of the duration when
 355     /// represented by microseconds. The returned number always represents a
 356     /// fractional portion of a second (i.e., it is less than one million).
 357     ///
 358     /// # Examples
 359     ///
 360     /// ```
 361     /// use std::time::Duration;
 362     ///
 363     /// let duration = Duration::from_micros(1_234_567);
 364     /// assert_eq!(duration.as_secs(), 1);
 365     /// assert_eq!(duration.subsec_micros(), 234_567);
 366     /// ```
 367     #[stable(feature = "duration_extras", since = "1.27.0")]
 368     #[rustc_const_stable(feature = "duration_extras", since = "1.32.0")]
 369     #[inline]
 370     pub const fn subsec_micros(&self) -> u32 {
 371         self.nanos / NANOS_PER_MICRO
 372     }
 373
 374     /// Returns the fractional part of this `Duration`, in nanoseconds.
 375     ///
 376     /// This method does **not** return the length of the duration when
 377     /// represented by nanoseconds. The returned number always represents a
 378     /// fractional portion of a second (i.e., it is less than one billion).
 379     ///
 380     /// # Examples
 381     ///
 382     /// ```
 383     /// use std::time::Duration;
 384     ///
 385     /// let duration = Duration::from_millis(5010);
 386     /// assert_eq!(duration.as_secs(), 5);
 387     /// assert_eq!(duration.subsec_nanos(), 10_000_000);
 388     /// ```
 389     #[stable(feature = "duration", since = "1.3.0")]
 390     #[rustc_const_stable(feature = "duration", since = "1.32.0")]
 391     #[inline]
 392     pub const fn subsec_nanos(&self) -> u32 {
 393         self.nanos
 394     }
 395
 396     /// Returns the total number of whole milliseconds contained by this `Duration`.
 397     ///
 398     /// # Examples
 399     ///
 400     /// ```
 401     /// use std::time::Duration;
 402     ///
 403     /// let duration = Duration::new(5, 730023852);
 404     /// assert_eq!(duration.as_millis(), 5730);
 405     /// ```
 406     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 407     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 408     #[inline]
 409     pub const fn as_millis(&self) -> u128 {
 410         self.secs as u128 * MILLIS_PER_SEC as u128 + (self.nanos / NANOS_PER_MILLI) as u128
 411     }
 412
 413     /// Returns the total number of whole microseconds contained by this `Duration`.
 414     ///
 415     /// # Examples
 416     ///
 417     /// ```
 418     /// use std::time::Duration;
 419     ///
 420     /// let duration = Duration::new(5, 730023852);
 421     /// assert_eq!(duration.as_micros(), 5730023);
 422     /// ```
 423     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 424     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 425     #[inline]
 426     pub const fn as_micros(&self) -> u128 {
 427         self.secs as u128 * MICROS_PER_SEC as u128 + (self.nanos / NANOS_PER_MICRO) as u128
 428     }
 429
 430     /// Returns the total number of nanoseconds contained by this `Duration`.
 431     ///
 432     /// # Examples
 433     ///
 434     /// ```
 435     /// use std::time::Duration;
 436     ///
 437     /// let duration = Duration::new(5, 730023852);
 438     /// assert_eq!(duration.as_nanos(), 5730023852);
 439     /// ```
 440     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 441     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 442     #[inline]
 443     pub const fn as_nanos(&self) -> u128 {
 444         self.secs as u128 * NANOS_PER_SEC as u128 + self.nanos as u128
 445     }
 446
 447     /// Checked `Duration` addition. Computes `self + other`, returning [`None`]
 448     /// if overflow occurred.
 449     ///
 450     /// # Examples
 451     ///
 452     /// Basic usage:
 453     ///
 454     /// ```
 455     /// use std::time::Duration;
 456     ///
 457     /// assert_eq!(Duration::new(0, 0).checked_add(Duration::new(0, 1)), Some(Duration::new(0, 1)));
 458     /// assert_eq!(Duration::new(1, 0).checked_add(Duration::new(u64::MAX, 0)), None);
 459     /// ```
 460     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 461     #[inline]
 462     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 463     pub const fn checked_add(self, rhs: Duration) -> Option<Duration> {
 464         if let Some(mut secs) = self.secs.checked_add(rhs.secs) {
 465             let mut nanos = self.nanos + rhs.nanos;
 466             if nanos >= NANOS_PER_SEC {
 467                 nanos -= NANOS_PER_SEC;
 468                 if let Some(new_secs) = secs.checked_add(1) {
 469                     secs = new_secs;
 470                 } else {
 471                     return None;
 472                 }
 473             }
 474             debug_assert!(nanos < NANOS_PER_SEC);
 475             Some(Duration { secs, nanos })
 476         } else {
 477             None
 478         }
 479     }
 480
 481     /// Saturating `Duration` addition. Computes `self + other`, returning [`Duration::MAX`]
 482     /// if overflow occurred.
 483     ///
 484     /// # Examples
 485     ///
 486     /// ```
 487     /// #![feature(duration_saturating_ops)]
 488     /// #![feature(duration_constants)]
 489     /// use std::time::Duration;
 490     ///
 491     /// assert_eq!(Duration::new(0, 0).saturating_add(Duration::new(0, 1)), Duration::new(0, 1));
 492     /// assert_eq!(Duration::new(1, 0).saturating_add(Duration::new(u64::MAX, 0)), Duration::MAX);
 493     /// ```
 494     #[unstable(feature = "duration_saturating_ops", issue = "76416")]
 495     #[inline]
 496     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 497     pub const fn saturating_add(self, rhs: Duration) -> Duration {
 498         match self.checked_add(rhs) {
 499             Some(res) => res,
 500             None => Duration::MAX,
 501         }
 502     }
 503
 504     /// Checked `Duration` subtraction. Computes `self - other`, returning [`None`]
 505     /// if the result would be negative or if overflow occurred.
 506     ///
 507     /// # Examples
 508     ///
 509     /// Basic usage:
 510     ///
 511     /// ```
 512     /// use std::time::Duration;
 513     ///
 514     /// assert_eq!(Duration::new(0, 1).checked_sub(Duration::new(0, 0)), Some(Duration::new(0, 1)));
 515     /// assert_eq!(Duration::new(0, 0).checked_sub(Duration::new(0, 1)), None);
 516     /// ```
 517     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 518     #[inline]
 519     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 520     pub const fn checked_sub(self, rhs: Duration) -> Option<Duration> {
 521         if let Some(mut secs) = self.secs.checked_sub(rhs.secs) {
 522             let nanos = if self.nanos >= rhs.nanos {
 523                 self.nanos - rhs.nanos
 524             } else {
 525                 if let Some(sub_secs) = secs.checked_sub(1) {
 526                     secs = sub_secs;
 527                     self.nanos + NANOS_PER_SEC - rhs.nanos
 528                 } else {
 529                     return None;
 530                 }
 531             };
 532             debug_assert!(nanos < NANOS_PER_SEC);
 533             Some(Duration { secs, nanos })
 534         } else {
 535             None
 536         }
 537     }
 538
 539     /// Saturating `Duration` subtraction. Computes `self - other`, returning [`Duration::MIN`]
 540     /// if the result would be negative or if overflow occurred.
 541     ///
 542     /// # Examples
 543     ///
 544     /// ```
 545     /// #![feature(duration_saturating_ops)]
 546     /// #![feature(duration_constants)]
 547     /// use std::time::Duration;
 548     ///
 549     /// assert_eq!(Duration::new(0, 1).saturating_sub(Duration::new(0, 0)), Duration::new(0, 1));
 550     /// assert_eq!(Duration::new(0, 0).saturating_sub(Duration::new(0, 1)), Duration::MIN);
 551     /// ```
 552     #[unstable(feature = "duration_saturating_ops", issue = "76416")]
 553     #[inline]
 554     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 555     pub const fn saturating_sub(self, rhs: Duration) -> Duration {
 556         match self.checked_sub(rhs) {
 557             Some(res) => res,
 558             None => Duration::MIN,
 559         }
 560     }
 561
 562     /// Checked `Duration` multiplication. Computes `self * other`, returning
 563     /// [`None`] if overflow occurred.
 564     ///
 565     /// # Examples
 566     ///
 567     /// Basic usage:
 568     ///
 569     /// ```
 570     /// use std::time::Duration;
 571     ///
 572     /// assert_eq!(Duration::new(0, 500_000_001).checked_mul(2), Some(Duration::new(1, 2)));
 573     /// assert_eq!(Duration::new(u64::MAX - 1, 0).checked_mul(2), None);
 574     /// ```
 575     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 576     #[inline]
 577     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 578     pub const fn checked_mul(self, rhs: u32) -> Option<Duration> {
 579         // Multiply nanoseconds as u64, because it cannot overflow that way.
 580         let total_nanos = self.nanos as u64 * rhs as u64;
 581         let extra_secs = total_nanos / (NANOS_PER_SEC as u64);
 582         let nanos = (total_nanos % (NANOS_PER_SEC as u64)) as u32;
 583         if let Some(s) = self.secs.checked_mul(rhs as u64) {
 584             if let Some(secs) = s.checked_add(extra_secs) {
 585                 debug_assert!(nanos < NANOS_PER_SEC);
 586                 return Some(Duration { secs, nanos });
 587             }
 588         }
 589         None
 590     }
 591
 592     /// Saturating `Duration` multiplication. Computes `self * other`, returning
 593     /// [`Duration::MAX`] if overflow occurred.
 594     ///
 595     /// # Examples
 596     ///
 597     /// ```
 598     /// #![feature(duration_saturating_ops)]
 599     /// #![feature(duration_constants)]
 600     /// use std::time::Duration;
 601     ///
 602     /// assert_eq!(Duration::new(0, 500_000_001).saturating_mul(2), Duration::new(1, 2));
 603     /// assert_eq!(Duration::new(u64::MAX - 1, 0).saturating_mul(2), Duration::MAX);
 604     /// ```
 605     #[unstable(feature = "duration_saturating_ops", issue = "76416")]
 606     #[inline]
 607     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 608     pub const fn saturating_mul(self, rhs: u32) -> Duration {
 609         match self.checked_mul(rhs) {
 610             Some(res) => res,
 611             None => Duration::MAX,
 612         }
 613     }
 614
 615     /// Checked `Duration` division. Computes `self / other`, returning [`None`]
 616     /// if `other == 0`.
 617     ///
 618     /// # Examples
 619     ///
 620     /// Basic usage:
 621     ///
 622     /// ```
 623     /// use std::time::Duration;
 624     ///
 625     /// assert_eq!(Duration::new(2, 0).checked_div(2), Some(Duration::new(1, 0)));
 626     /// assert_eq!(Duration::new(1, 0).checked_div(2), Some(Duration::new(0, 500_000_000)));
 627     /// assert_eq!(Duration::new(2, 0).checked_div(0), None);
 628     /// ```
 629     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 630     #[inline]
 631     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 632     pub const fn checked_div(self, rhs: u32) -> Option<Duration> {
 633         if rhs != 0 {
 634             let secs = self.secs / (rhs as u64);
 635             let carry = self.secs - secs * (rhs as u64);
 636             let extra_nanos = carry * (NANOS_PER_SEC as u64) / (rhs as u64);
 637             let nanos = self.nanos / rhs + (extra_nanos as u32);
 638             debug_assert!(nanos < NANOS_PER_SEC);
 639             Some(Duration { secs, nanos })
 640         } else {
 641             None
 642         }
 643     }
 644
 645     /// Returns the number of seconds contained by this `Duration` as `f64`.
 646     ///
 647     /// The returned value does include the fractional (nanosecond) part of the duration.
 648     ///
 649     /// # Examples
 650     /// ```
 651     /// use std::time::Duration;
 652     ///
 653     /// let dur = Duration::new(2, 700_000_000);
 654     /// assert_eq!(dur.as_secs_f64(), 2.7);
 655     /// ```
 656     #[stable(feature = "duration_float", since = "1.38.0")]
 657     #[inline]
 658     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 659     pub const fn as_secs_f64(&self) -> f64 {
 660         (self.secs as f64) + (self.nanos as f64) / (NANOS_PER_SEC as f64)
 661     }
 662
 663     /// Returns the number of seconds contained by this `Duration` as `f32`.
 664     ///
 665     /// The returned value does include the fractional (nanosecond) part of the duration.
 666     ///
 667     /// # Examples
 668     /// ```
 669     /// use std::time::Duration;
 670     ///
 671     /// let dur = Duration::new(2, 700_000_000);
 672     /// assert_eq!(dur.as_secs_f32(), 2.7);
 673     /// ```
 674     #[stable(feature = "duration_float", since = "1.38.0")]
 675     #[inline]
 676     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 677     pub const fn as_secs_f32(&self) -> f32 {
 678         (self.secs as f32) + (self.nanos as f32) / (NANOS_PER_SEC as f32)
 679     }
 680
 681     /// Creates a new `Duration` from the specified number of seconds represented
 682     /// as `f64`.
 683     ///
 684     /// # Panics
 685     /// This constructor will panic if `secs` is not finite, negative or overflows `Duration`.
 686     ///
 687     /// # Examples
 688     /// ```
 689     /// use std::time::Duration;
 690     ///
 691     /// let dur = Duration::from_secs_f64(2.7);
 692     /// assert_eq!(dur, Duration::new(2, 700_000_000));
 693     /// ```
 694     #[stable(feature = "duration_float", since = "1.38.0")]
 695     #[inline]
 696     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 697     pub const fn from_secs_f64(secs: f64) -> Duration {
 698         const MAX_NANOS_F64: f64 = ((u64::MAX as u128 + 1) * (NANOS_PER_SEC as u128)) as f64;
 699         let nanos = secs * (NANOS_PER_SEC as f64);
 700         if !nanos.is_finite() {
 701             panic!("got non-finite value when converting float to duration");
 702         }
 703         if nanos >= MAX_NANOS_F64 {
 704             panic!("overflow when converting float to duration");
 705         }
 706         if nanos < 0.0 {
 707             panic!("underflow when converting float to duration");
 708         }
 709         let nanos = nanos as u128;
 710         Duration {
 711             secs: (nanos / (NANOS_PER_SEC as u128)) as u64,
 712             nanos: (nanos % (NANOS_PER_SEC as u128)) as u32,
 713         }
 714     }
 715
 716     /// Creates a new `Duration` from the specified number of seconds represented
 717     /// as `f32`.
 718     ///
 719     /// # Panics
 720     /// This constructor will panic if `secs` is not finite, negative or overflows `Duration`.
 721     ///
 722     /// # Examples
 723     /// ```
 724     /// use std::time::Duration;
 725     ///
 726     /// let dur = Duration::from_secs_f32(2.7);
 727     /// assert_eq!(dur, Duration::new(2, 700_000_000));
 728     /// ```
 729     #[stable(feature = "duration_float", since = "1.38.0")]
 730     #[inline]
 731     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 732     pub const fn from_secs_f32(secs: f32) -> Duration {
 733         const MAX_NANOS_F32: f32 = ((u64::MAX as u128 + 1) * (NANOS_PER_SEC as u128)) as f32;
 734         let nanos = secs * (NANOS_PER_SEC as f32);
 735         if !nanos.is_finite() {
 736             panic!("got non-finite value when converting float to duration");
 737         }
 738         if nanos >= MAX_NANOS_F32 {
 739             panic!("overflow when converting float to duration");
 740         }
 741         if nanos < 0.0 {
 742             panic!("underflow when converting float to duration");
 743         }
 744         let nanos = nanos as u128;
 745         Duration {
 746             secs: (nanos / (NANOS_PER_SEC as u128)) as u64,
 747             nanos: (nanos % (NANOS_PER_SEC as u128)) as u32,
 748         }
 749     }
 750
 751     /// Multiplies `Duration` by `f64`.
 752     ///
 753     /// # Panics
 754     /// This method will panic if result is not finite, negative or overflows `Duration`.
 755     ///
 756     /// # Examples
 757     /// ```
 758     /// use std::time::Duration;
 759     ///
 760     /// let dur = Duration::new(2, 700_000_000);
 761     /// assert_eq!(dur.mul_f64(3.14), Duration::new(8, 478_000_000));
 762     /// assert_eq!(dur.mul_f64(3.14e5), Duration::new(847_800, 0));
 763     /// ```
 764     #[stable(feature = "duration_float", since = "1.38.0")]
 765     #[inline]
 766     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 767     pub const fn mul_f64(self, rhs: f64) -> Duration {
 768         Duration::from_secs_f64(rhs * self.as_secs_f64())
 769     }
 770
 771     /// Multiplies `Duration` by `f32`.
 772     ///
 773     /// # Panics
 774     /// This method will panic if result is not finite, negative or overflows `Duration`.
 775     ///
 776     /// # Examples
 777     /// ```
 778     /// use std::time::Duration;
 779     ///
 780     /// let dur = Duration::new(2, 700_000_000);
 781     /// // note that due to rounding errors result is slightly different
 782     /// // from 8.478 and 847800.0
 783     /// assert_eq!(dur.mul_f32(3.14), Duration::new(8, 478_000_640));
 784     /// assert_eq!(dur.mul_f32(3.14e5), Duration::new(847799, 969_120_256));
 785     /// ```
 786     #[stable(feature = "duration_float", since = "1.38.0")]
 787     #[inline]
 788     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 789     pub const fn mul_f32(self, rhs: f32) -> Duration {
 790         Duration::from_secs_f32(rhs * self.as_secs_f32())
 791     }
 792
 793     /// Divide `Duration` by `f64`.
 794     ///
 795     /// # Panics
 796     /// This method will panic if result is not finite, negative or overflows `Duration`.
 797     ///
 798     /// # Examples
 799     /// ```
 800     /// use std::time::Duration;
 801     ///
 802     /// let dur = Duration::new(2, 700_000_000);
 803     /// assert_eq!(dur.div_f64(3.14), Duration::new(0, 859_872_611));
 804     /// // note that truncation is used, not rounding
 805     /// assert_eq!(dur.div_f64(3.14e5), Duration::new(0, 8_598));
 806     /// ```
 807     #[stable(feature = "duration_float", since = "1.38.0")]
 808     #[inline]
 809     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 810     pub const fn div_f64(self, rhs: f64) -> Duration {
 811         Duration::from_secs_f64(self.as_secs_f64() / rhs)
 812     }
 813
 814     /// Divide `Duration` by `f32`.
 815     ///
 816     /// # Panics
 817     /// This method will panic if result is not finite, negative or overflows `Duration`.
 818     ///
 819     /// # Examples
 820     /// ```
 821     /// use std::time::Duration;
 822     ///
 823     /// let dur = Duration::new(2, 700_000_000);
 824     /// // note that due to rounding errors result is slightly
 825     /// // different from 0.859_872_611
 826     /// assert_eq!(dur.div_f32(3.14), Duration::new(0, 859_872_576));
 827     /// // note that truncation is used, not rounding
 828     /// assert_eq!(dur.div_f32(3.14e5), Duration::new(0, 8_598));
 829     /// ```
 830     #[stable(feature = "duration_float", since = "1.38.0")]
 831     #[inline]
 832     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 833     pub const fn div_f32(self, rhs: f32) -> Duration {
 834         Duration::from_secs_f32(self.as_secs_f32() / rhs)
 835     }
 836
 837     /// Divide `Duration` by `Duration` and return `f64`.
 838     ///
 839     /// # Examples
 840     /// ```
 841     /// #![feature(div_duration)]
 842     /// use std::time::Duration;
 843     ///
 844     /// let dur1 = Duration::new(2, 700_000_000);
 845     /// let dur2 = Duration::new(5, 400_000_000);
 846     /// assert_eq!(dur1.div_duration_f64(dur2), 0.5);
 847     /// ```
 848     #[unstable(feature = "div_duration", issue = "63139")]
 849     #[inline]
 850     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 851     pub const fn div_duration_f64(self, rhs: Duration) -> f64 {
 852         self.as_secs_f64() / rhs.as_secs_f64()
 853     }
 854
 855     /// Divide `Duration` by `Duration` and return `f32`.
 856     ///
 857     /// # Examples
 858     /// ```
 859     /// #![feature(div_duration)]
 860     /// use std::time::Duration;
 861     ///
 862     /// let dur1 = Duration::new(2, 700_000_000);
 863     /// let dur2 = Duration::new(5, 400_000_000);
 864     /// assert_eq!(dur1.div_duration_f32(dur2), 0.5);
 865     /// ```
 866     #[unstable(feature = "div_duration", issue = "63139")]
 867     #[inline]
 868     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 869     pub const fn div_duration_f32(self, rhs: Duration) -> f32 {
 870         self.as_secs_f32() / rhs.as_secs_f32()
 871     }
 872 }
 873
 874 #[stable(feature = "duration", since = "1.3.0")]
 875 impl Add for Duration {
 876     type Output = Duration;
 877
 878     fn add(self, rhs: Duration) -> Duration {
 879         self.checked_add(rhs).expect("overflow when adding durations")
 880     }
 881 }
 882
 883 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 884 impl AddAssign for Duration {
 885     fn add_assign(&mut self, rhs: Duration) {
 886         *self = *self + rhs;
 887     }
 888 }
 889
 890 #[stable(feature = "duration", since = "1.3.0")]
 891 impl Sub for Duration {
 892     type Output = Duration;
 893
 894     fn sub(self, rhs: Duration) -> Duration {
 895         self.checked_sub(rhs).expect("overflow when subtracting durations")
 896     }
 897 }
 898
 899 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 900 impl SubAssign for Duration {
 901     fn sub_assign(&mut self, rhs: Duration) {
 902         *self = *self - rhs;
 903     }
 904 }
 905
 906 #[stable(feature = "duration", since = "1.3.0")]
 907 impl Mul<u32> for Duration {
 908     type Output = Duration;
 909
 910     fn mul(self, rhs: u32) -> Duration {
 911         self.checked_mul(rhs).expect("overflow when multiplying duration by scalar")
 912     }
 913 }
 914
 915 #[stable(feature = "symmetric_u32_duration_mul", since = "1.31.0")]
 916 impl Mul<Duration> for u32 {
 917     type Output = Duration;
 918
 919     fn mul(self, rhs: Duration) -> Duration {
 920         rhs * self
 921     }
 922 }
 923
 924 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 925 impl MulAssign<u32> for Duration {
 926     fn mul_assign(&mut self, rhs: u32) {
 927         *self = *self * rhs;
 928     }
 929 }
 930
 931 #[stable(feature = "duration", since = "1.3.0")]
 932 impl Div<u32> for Duration {
 933     type Output = Duration;
 934
 935     fn div(self, rhs: u32) -> Duration {
 936         self.checked_div(rhs).expect("divide by zero error when dividing duration by scalar")
 937     }
 938 }
 939
 940 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 941 impl DivAssign<u32> for Duration {
 942     fn div_assign(&mut self, rhs: u32) {
 943         *self = *self / rhs;
 944     }
 945 }
 946
 947 macro_rules! sum_durations {
 948     ($iter:expr) => {{
 949         let mut total_secs: u64 = 0;
 950         let mut total_nanos: u64 = 0;
 951
 952         for entry in $iter {
 953             total_secs =
 954                 total_secs.checked_add(entry.secs).expect("overflow in iter::sum over durations");
 955             total_nanos = match total_nanos.checked_add(entry.nanos as u64) {
 956                 Some(n) => n,
 957                 None => {
 958                     total_secs = total_secs
 959                         .checked_add(total_nanos / NANOS_PER_SEC as u64)
 960                         .expect("overflow in iter::sum over durations");
 961                     (total_nanos % NANOS_PER_SEC as u64) + entry.nanos as u64
 962                 }
 963             };
 964         }
 965         total_secs = total_secs
 966             .checked_add(total_nanos / NANOS_PER_SEC as u64)
 967             .expect("overflow in iter::sum over durations");
 968         total_nanos = total_nanos % NANOS_PER_SEC as u64;
 969         Duration { secs: total_secs, nanos: total_nanos as u32 }
 970     }};
 971 }
 972
 973 #[stable(feature = "duration_sum", since = "1.16.0")]
 974 impl Sum for Duration {
 975     fn sum<I: Iterator<Item = Duration>>(iter: I) -> Duration {
 976         sum_durations!(iter)
 977     }
 978 }
 979
 980 #[stable(feature = "duration_sum", since = "1.16.0")]
 981 impl<'a> Sum<&'a Duration> for Duration {
 982     fn sum<I: Iterator<Item = &'a Duration>>(iter: I) -> Duration {
 983         sum_durations!(iter)
 984     }
 985 }
 986
 987 #[stable(feature = "duration_debug_impl", since = "1.27.0")]
 988 impl fmt::Debug for Duration {
 989     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 990         /// Formats a floating point number in decimal notation.
 991         ///
 992         /// The number is given as the `integer_part` and a fractional part.
 993         /// The value of the fractional part is `fractional_part / divisor`. So
 994         /// `integer_part` = 3, `fractional_part` = 12 and `divisor` = 100
 995         /// represents the number `3.012`. Trailing zeros are omitted.
 996         ///
 997         /// `divisor` must not be above 100_000_000. It also should be a power
 998         /// of 10, everything else doesn't make sense. `fractional_part` has
 999         /// to be less than `10 * divisor`!
1000         fn fmt_decimal(
1001             f: &mut fmt::Formatter<'_>,
1002             mut integer_part: u64,
1003             mut fractional_part: u32,
1004             mut divisor: u32,
1005         ) -> fmt::Result {
1006             // Encode the fractional part into a temporary buffer. The buffer
1007             // only need to hold 9 elements, because `fractional_part` has to
1008             // be smaller than 10^9. The buffer is prefilled with '0' digits
1009             // to simplify the code below.
1010             let mut buf = [b'0'; 9];
1011
1012             // The next digit is written at this position
1013             let mut pos = 0;
1014
1015             // We keep writing digits into the buffer while there are non-zero
1016             // digits left and we haven't written enough digits yet.
1017             while fractional_part > 0 && pos < f.precision().unwrap_or(9) {
1018                 // Write new digit into the buffer
1019                 buf[pos] = b'0' + (fractional_part / divisor) as u8;
1020
1021                 fractional_part %= divisor;
1022                 divisor /= 10;
1023                 pos += 1;
1024             }
1025
1026             // If a precision < 9 was specified, there may be some non-zero
1027             // digits left that weren't written into the buffer. In that case we
1028             // need to perform rounding to match the semantics of printing
1029             // normal floating point numbers. However, we only need to do work
1030             // when rounding up. This happens if the first digit of the
1031             // remaining ones is >= 5.
1032             if fractional_part > 0 && fractional_part >= divisor * 5 {
1033                 // Round up the number contained in the buffer. We go through
1034                 // the buffer backwards and keep track of the carry.
1035                 let mut rev_pos = pos;
1036                 let mut carry = true;
1037                 while carry && rev_pos > 0 {
1038                     rev_pos -= 1;
1039
1040                     // If the digit in the buffer is not '9', we just need to
1041                     // increment it and can stop then (since we don't have a
1042                     // carry anymore). Otherwise, we set it to '0' (overflow)
1043                     // and continue.
1044                     if buf[rev_pos] < b'9' {
1045                         buf[rev_pos] += 1;
1046                         carry = false;
1047                     } else {
1048                         buf[rev_pos] = b'0';
1049                     }
1050                 }
1051
1052                 // If we still have the carry bit set, that means that we set
1053                 // the whole buffer to '0's and need to increment the integer
1054                 // part.
1055                 if carry {
1056                     integer_part += 1;
1057                 }
1058             }
1059
1060             // Determine the end of the buffer: if precision is set, we just
1061             // use as many digits from the buffer (capped to 9). If it isn't
1062             // set, we only use all digits up to the last non-zero one.
1063             let end = f.precision().map(|p| crate::cmp::min(p, 9)).unwrap_or(pos);
1064
1065             // If we haven't emitted a single fractional digit and the precision
1066             // wasn't set to a non-zero value, we don't print the decimal point.
1067             if end == 0 {
1068                 write!(f, "{}", integer_part)
1069             } else {
1070                 // SAFETY: We are only writing ASCII digits into the buffer and it was
1071                 // initialized with '0's, so it contains valid UTF8.
1072                 let s = unsafe { crate::str::from_utf8_unchecked(&buf[..end]) };
1073
1074                 // If the user request a precision > 9, we pad '0's at the end.
1075                 let w = f.precision().unwrap_or(pos);
1076                 write!(f, "{}.{:0<width$}", integer_part, s, width = w)
1077             }
1078         }
1079
1080         // Print leading '+' sign if requested
1081         if f.sign_plus() {
1082             write!(f, "+")?;
1083         }
1084
1085         if self.secs > 0 {
1086             fmt_decimal(f, self.secs, self.nanos, 100_000_000)?;
1087             f.write_str("s")
1088         } else if self.nanos >= 1_000_000 {
1089             fmt_decimal(f, self.nanos as u64 / 1_000_000, self.nanos % 1_000_000, 100_000)?;
1090             f.write_str("ms")
1091         } else if self.nanos >= 1_000 {
1092             fmt_decimal(f, self.nanos as u64 / 1_000, self.nanos % 1_000, 100)?;
1093             f.write_str("µs")
1094         } else {
1095             fmt_decimal(f, self.nanos as u64, 0, 1)?;
1096             f.write_str("ns")
1097         }
1098     }
1099 }