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 ///
  52 /// # Formatting `Duration` values
  53 ///
  54 /// `Duration` intentionally does not have a `Display` impl, as there are a
  55 /// variety of ways to format spans of time for human readability. `Duration`
  56 /// provides a `Debug` impl that shows the full precision of the value.
  57 ///
  58 /// The `Debug` output uses the non-ASCII "µs" suffix for microseconds. If your
  59 /// program output may appear in contexts that cannot rely on full Unicode
  60 /// compatibility, you may wish to format `Duration` objects yourself or use a
  61 /// crate to do so.
  62 #[stable(feature = "duration", since = "1.3.0")]
  63 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
  64 pub struct Duration {
  65     secs: u64,
  66     nanos: u32, // Always 0 <= nanos < NANOS_PER_SEC
  67 }
  68
  69 impl Duration {
  70     /// The duration of one second.
  71     ///
  72     /// # Examples
  73     ///
  74     /// ```
  75     /// #![feature(duration_constants)]
  76     /// use std::time::Duration;
  77     ///
  78     /// assert_eq!(Duration::SECOND, Duration::from_secs(1));
  79     /// ```
  80     #[unstable(feature = "duration_constants", issue = "57391")]
  81     pub const SECOND: Duration = Duration::from_secs(1);
  82
  83     /// The duration of one millisecond.
  84     ///
  85     /// # Examples
  86     ///
  87     /// ```
  88     /// #![feature(duration_constants)]
  89     /// use std::time::Duration;
  90     ///
  91     /// assert_eq!(Duration::MILLISECOND, Duration::from_millis(1));
  92     /// ```
  93     #[unstable(feature = "duration_constants", issue = "57391")]
  94     pub const MILLISECOND: Duration = Duration::from_millis(1);
  95
  96     /// The duration of one microsecond.
  97     ///
  98     /// # Examples
  99     ///
 100     /// ```
 101     /// #![feature(duration_constants)]
 102     /// use std::time::Duration;
 103     ///
 104     /// assert_eq!(Duration::MICROSECOND, Duration::from_micros(1));
 105     /// ```
 106     #[unstable(feature = "duration_constants", issue = "57391")]
 107     pub const MICROSECOND: Duration = Duration::from_micros(1);
 108
 109     /// The duration of one nanosecond.
 110     ///
 111     /// # Examples
 112     ///
 113     /// ```
 114     /// #![feature(duration_constants)]
 115     /// use std::time::Duration;
 116     ///
 117     /// assert_eq!(Duration::NANOSECOND, Duration::from_nanos(1));
 118     /// ```
 119     #[unstable(feature = "duration_constants", issue = "57391")]
 120     pub const NANOSECOND: Duration = Duration::from_nanos(1);
 121
 122     /// A duration of zero time.
 123     ///
 124     /// # Examples
 125     ///
 126     /// ```
 127     /// #![feature(duration_zero)]
 128     /// use std::time::Duration;
 129     ///
 130     /// let duration = Duration::ZERO;
 131     /// assert!(duration.is_zero());
 132     /// assert_eq!(duration.as_nanos(), 0);
 133     /// ```
 134     #[unstable(feature = "duration_zero", issue = "73544")]
 135     pub const ZERO: Duration = Duration::from_nanos(0);
 136
 137     /// The maximum duration.
 138     ///
 139     /// It is roughly equal to a duration of 584,942,417,355 years.
 140     ///
 141     /// # Examples
 142     ///
 143     /// ```
 144     /// #![feature(duration_constants)]
 145     /// use std::time::Duration;
 146     ///
 147     /// assert_eq!(Duration::MAX, Duration::new(u64::MAX, 1_000_000_000 - 1));
 148     /// ```
 149     #[unstable(feature = "duration_constants", issue = "57391")]
 150     pub const MAX: Duration = Duration::new(u64::MAX, NANOS_PER_SEC - 1);
 151
 152     /// Creates a new `Duration` from the specified number of whole seconds and
 153     /// additional nanoseconds.
 154     ///
 155     /// If the number of nanoseconds is greater than 1 billion (the number of
 156     /// nanoseconds in a second), then it will carry over into the seconds provided.
 157     ///
 158     /// # Panics
 159     ///
 160     /// This constructor will panic if the carry from the nanoseconds overflows
 161     /// the seconds counter.
 162     ///
 163     /// # Examples
 164     ///
 165     /// ```
 166     /// use std::time::Duration;
 167     ///
 168     /// let five_seconds = Duration::new(5, 0);
 169     /// ```
 170     #[stable(feature = "duration", since = "1.3.0")]
 171     #[inline]
 172     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 173     pub const fn new(secs: u64, nanos: u32) -> Duration {
 174         let secs = match secs.checked_add((nanos / NANOS_PER_SEC) as u64) {
 175             Some(secs) => secs,
 176             None => panic!("overflow in Duration::new"),
 177         };
 178         let nanos = nanos % NANOS_PER_SEC;
 179         Duration { secs, nanos }
 180     }
 181
 182     /// Creates a new `Duration` from the specified number of whole seconds.
 183     ///
 184     /// # Examples
 185     ///
 186     /// ```
 187     /// use std::time::Duration;
 188     ///
 189     /// let duration = Duration::from_secs(5);
 190     ///
 191     /// assert_eq!(5, duration.as_secs());
 192     /// assert_eq!(0, duration.subsec_nanos());
 193     /// ```
 194     #[stable(feature = "duration", since = "1.3.0")]
 195     #[inline]
 196     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 197     pub const fn from_secs(secs: u64) -> Duration {
 198         Duration { secs, nanos: 0 }
 199     }
 200
 201     /// Creates a new `Duration` from the specified number of milliseconds.
 202     ///
 203     /// # Examples
 204     ///
 205     /// ```
 206     /// use std::time::Duration;
 207     ///
 208     /// let duration = Duration::from_millis(2569);
 209     ///
 210     /// assert_eq!(2, duration.as_secs());
 211     /// assert_eq!(569_000_000, duration.subsec_nanos());
 212     /// ```
 213     #[stable(feature = "duration", since = "1.3.0")]
 214     #[inline]
 215     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 216     pub const fn from_millis(millis: u64) -> Duration {
 217         Duration {
 218             secs: millis / MILLIS_PER_SEC,
 219             nanos: ((millis % MILLIS_PER_SEC) as u32) * NANOS_PER_MILLI,
 220         }
 221     }
 222
 223     /// Creates a new `Duration` from the specified number of microseconds.
 224     ///
 225     /// # Examples
 226     ///
 227     /// ```
 228     /// use std::time::Duration;
 229     ///
 230     /// let duration = Duration::from_micros(1_000_002);
 231     ///
 232     /// assert_eq!(1, duration.as_secs());
 233     /// assert_eq!(2000, duration.subsec_nanos());
 234     /// ```
 235     #[stable(feature = "duration_from_micros", since = "1.27.0")]
 236     #[inline]
 237     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 238     pub const fn from_micros(micros: u64) -> Duration {
 239         Duration {
 240             secs: micros / MICROS_PER_SEC,
 241             nanos: ((micros % MICROS_PER_SEC) as u32) * NANOS_PER_MICRO,
 242         }
 243     }
 244
 245     /// Creates a new `Duration` from the specified number of nanoseconds.
 246     ///
 247     /// # Examples
 248     ///
 249     /// ```
 250     /// use std::time::Duration;
 251     ///
 252     /// let duration = Duration::from_nanos(1_000_000_123);
 253     ///
 254     /// assert_eq!(1, duration.as_secs());
 255     /// assert_eq!(123, duration.subsec_nanos());
 256     /// ```
 257     #[stable(feature = "duration_extras", since = "1.27.0")]
 258     #[inline]
 259     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 260     pub const fn from_nanos(nanos: u64) -> Duration {
 261         Duration {
 262             secs: nanos / (NANOS_PER_SEC as u64),
 263             nanos: (nanos % (NANOS_PER_SEC as u64)) as u32,
 264         }
 265     }
 266
 267     /// Returns true if this `Duration` spans no time.
 268     ///
 269     /// # Examples
 270     ///
 271     /// ```
 272     /// #![feature(duration_zero)]
 273     /// use std::time::Duration;
 274     ///
 275     /// assert!(Duration::ZERO.is_zero());
 276     /// assert!(Duration::new(0, 0).is_zero());
 277     /// assert!(Duration::from_nanos(0).is_zero());
 278     /// assert!(Duration::from_secs(0).is_zero());
 279     ///
 280     /// assert!(!Duration::new(1, 1).is_zero());
 281     /// assert!(!Duration::from_nanos(1).is_zero());
 282     /// assert!(!Duration::from_secs(1).is_zero());
 283     /// ```
 284     #[unstable(feature = "duration_zero", issue = "73544")]
 285     #[inline]
 286     pub const fn is_zero(&self) -> bool {
 287         self.secs == 0 && self.nanos == 0
 288     }
 289
 290     /// Returns the number of _whole_ seconds contained by this `Duration`.
 291     ///
 292     /// The returned value does not include the fractional (nanosecond) part of the
 293     /// duration, which can be obtained using [`subsec_nanos`].
 294     ///
 295     /// # Examples
 296     ///
 297     /// ```
 298     /// use std::time::Duration;
 299     ///
 300     /// let duration = Duration::new(5, 730023852);
 301     /// assert_eq!(duration.as_secs(), 5);
 302     /// ```
 303     ///
 304     /// To determine the total number of seconds represented by the `Duration`,
 305     /// use `as_secs` in combination with [`subsec_nanos`]:
 306     ///
 307     /// ```
 308     /// use std::time::Duration;
 309     ///
 310     /// let duration = Duration::new(5, 730023852);
 311     ///
 312     /// assert_eq!(5.730023852,
 313     ///            duration.as_secs() as f64
 314     ///            + duration.subsec_nanos() as f64 * 1e-9);
 315     /// ```
 316     ///
 317     /// [`subsec_nanos`]: Duration::subsec_nanos
 318     #[stable(feature = "duration", since = "1.3.0")]
 319     #[rustc_const_stable(feature = "duration", since = "1.32.0")]
 320     #[inline]
 321     pub const fn as_secs(&self) -> u64 {
 322         self.secs
 323     }
 324
 325     /// Returns the fractional part of this `Duration`, in whole milliseconds.
 326     ///
 327     /// This method does **not** return the length of the duration when
 328     /// represented by milliseconds. The returned number always represents a
 329     /// fractional portion of a second (i.e., it is less than one thousand).
 330     ///
 331     /// # Examples
 332     ///
 333     /// ```
 334     /// use std::time::Duration;
 335     ///
 336     /// let duration = Duration::from_millis(5432);
 337     /// assert_eq!(duration.as_secs(), 5);
 338     /// assert_eq!(duration.subsec_millis(), 432);
 339     /// ```
 340     #[stable(feature = "duration_extras", since = "1.27.0")]
 341     #[rustc_const_stable(feature = "duration_extras", since = "1.32.0")]
 342     #[inline]
 343     pub const fn subsec_millis(&self) -> u32 {
 344         self.nanos / NANOS_PER_MILLI
 345     }
 346
 347     /// Returns the fractional part of this `Duration`, in whole microseconds.
 348     ///
 349     /// This method does **not** return the length of the duration when
 350     /// represented by microseconds. The returned number always represents a
 351     /// fractional portion of a second (i.e., it is less than one million).
 352     ///
 353     /// # Examples
 354     ///
 355     /// ```
 356     /// use std::time::Duration;
 357     ///
 358     /// let duration = Duration::from_micros(1_234_567);
 359     /// assert_eq!(duration.as_secs(), 1);
 360     /// assert_eq!(duration.subsec_micros(), 234_567);
 361     /// ```
 362     #[stable(feature = "duration_extras", since = "1.27.0")]
 363     #[rustc_const_stable(feature = "duration_extras", since = "1.32.0")]
 364     #[inline]
 365     pub const fn subsec_micros(&self) -> u32 {
 366         self.nanos / NANOS_PER_MICRO
 367     }
 368
 369     /// Returns the fractional part of this `Duration`, in nanoseconds.
 370     ///
 371     /// This method does **not** return the length of the duration when
 372     /// represented by nanoseconds. The returned number always represents a
 373     /// fractional portion of a second (i.e., it is less than one billion).
 374     ///
 375     /// # Examples
 376     ///
 377     /// ```
 378     /// use std::time::Duration;
 379     ///
 380     /// let duration = Duration::from_millis(5010);
 381     /// assert_eq!(duration.as_secs(), 5);
 382     /// assert_eq!(duration.subsec_nanos(), 10_000_000);
 383     /// ```
 384     #[stable(feature = "duration", since = "1.3.0")]
 385     #[rustc_const_stable(feature = "duration", since = "1.32.0")]
 386     #[inline]
 387     pub const fn subsec_nanos(&self) -> u32 {
 388         self.nanos
 389     }
 390
 391     /// Returns the total number of whole milliseconds contained by this `Duration`.
 392     ///
 393     /// # Examples
 394     ///
 395     /// ```
 396     /// use std::time::Duration;
 397     ///
 398     /// let duration = Duration::new(5, 730023852);
 399     /// assert_eq!(duration.as_millis(), 5730);
 400     /// ```
 401     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 402     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 403     #[inline]
 404     pub const fn as_millis(&self) -> u128 {
 405         self.secs as u128 * MILLIS_PER_SEC as u128 + (self.nanos / NANOS_PER_MILLI) as u128
 406     }
 407
 408     /// Returns the total number of whole microseconds contained by this `Duration`.
 409     ///
 410     /// # Examples
 411     ///
 412     /// ```
 413     /// use std::time::Duration;
 414     ///
 415     /// let duration = Duration::new(5, 730023852);
 416     /// assert_eq!(duration.as_micros(), 5730023);
 417     /// ```
 418     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 419     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 420     #[inline]
 421     pub const fn as_micros(&self) -> u128 {
 422         self.secs as u128 * MICROS_PER_SEC as u128 + (self.nanos / NANOS_PER_MICRO) as u128
 423     }
 424
 425     /// Returns the total number of nanoseconds contained by this `Duration`.
 426     ///
 427     /// # Examples
 428     ///
 429     /// ```
 430     /// use std::time::Duration;
 431     ///
 432     /// let duration = Duration::new(5, 730023852);
 433     /// assert_eq!(duration.as_nanos(), 5730023852);
 434     /// ```
 435     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 436     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 437     #[inline]
 438     pub const fn as_nanos(&self) -> u128 {
 439         self.secs as u128 * NANOS_PER_SEC as u128 + self.nanos as u128
 440     }
 441
 442     /// Checked `Duration` addition. Computes `self + other`, returning [`None`]
 443     /// if overflow occurred.
 444     ///
 445     /// # Examples
 446     ///
 447     /// Basic usage:
 448     ///
 449     /// ```
 450     /// use std::time::Duration;
 451     ///
 452     /// assert_eq!(Duration::new(0, 0).checked_add(Duration::new(0, 1)), Some(Duration::new(0, 1)));
 453     /// assert_eq!(Duration::new(1, 0).checked_add(Duration::new(u64::MAX, 0)), None);
 454     /// ```
 455     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 456     #[inline]
 457     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 458     pub const fn checked_add(self, rhs: Duration) -> Option<Duration> {
 459         if let Some(mut secs) = self.secs.checked_add(rhs.secs) {
 460             let mut nanos = self.nanos + rhs.nanos;
 461             if nanos >= NANOS_PER_SEC {
 462                 nanos -= NANOS_PER_SEC;
 463                 if let Some(new_secs) = secs.checked_add(1) {
 464                     secs = new_secs;
 465                 } else {
 466                     return None;
 467                 }
 468             }
 469             debug_assert!(nanos < NANOS_PER_SEC);
 470             Some(Duration { secs, nanos })
 471         } else {
 472             None
 473         }
 474     }
 475
 476     /// Saturating `Duration` addition. Computes `self + other`, returning [`Duration::MAX`]
 477     /// if overflow occurred.
 478     ///
 479     /// # Examples
 480     ///
 481     /// ```
 482     /// #![feature(duration_saturating_ops)]
 483     /// #![feature(duration_constants)]
 484     /// use std::time::Duration;
 485     ///
 486     /// assert_eq!(Duration::new(0, 0).saturating_add(Duration::new(0, 1)), Duration::new(0, 1));
 487     /// assert_eq!(Duration::new(1, 0).saturating_add(Duration::new(u64::MAX, 0)), Duration::MAX);
 488     /// ```
 489     #[unstable(feature = "duration_saturating_ops", issue = "76416")]
 490     #[inline]
 491     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 492     pub const fn saturating_add(self, rhs: Duration) -> Duration {
 493         match self.checked_add(rhs) {
 494             Some(res) => res,
 495             None => Duration::MAX,
 496         }
 497     }
 498
 499     /// Checked `Duration` subtraction. Computes `self - other`, returning [`None`]
 500     /// if the result would be negative or if overflow occurred.
 501     ///
 502     /// # Examples
 503     ///
 504     /// Basic usage:
 505     ///
 506     /// ```
 507     /// use std::time::Duration;
 508     ///
 509     /// assert_eq!(Duration::new(0, 1).checked_sub(Duration::new(0, 0)), Some(Duration::new(0, 1)));
 510     /// assert_eq!(Duration::new(0, 0).checked_sub(Duration::new(0, 1)), None);
 511     /// ```
 512     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 513     #[inline]
 514     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 515     pub const fn checked_sub(self, rhs: Duration) -> Option<Duration> {
 516         if let Some(mut secs) = self.secs.checked_sub(rhs.secs) {
 517             let nanos = if self.nanos >= rhs.nanos {
 518                 self.nanos - rhs.nanos
 519             } else {
 520                 if let Some(sub_secs) = secs.checked_sub(1) {
 521                     secs = sub_secs;
 522                     self.nanos + NANOS_PER_SEC - rhs.nanos
 523                 } else {
 524                     return None;
 525                 }
 526             };
 527             debug_assert!(nanos < NANOS_PER_SEC);
 528             Some(Duration { secs, nanos })
 529         } else {
 530             None
 531         }
 532     }
 533
 534     /// Saturating `Duration` subtraction. Computes `self - other`, returning [`Duration::ZERO`]
 535     /// if the result would be negative or if overflow occurred.
 536     ///
 537     /// # Examples
 538     ///
 539     /// ```
 540     /// #![feature(duration_saturating_ops)]
 541     /// #![feature(duration_zero)]
 542     /// use std::time::Duration;
 543     ///
 544     /// assert_eq!(Duration::new(0, 1).saturating_sub(Duration::new(0, 0)), Duration::new(0, 1));
 545     /// assert_eq!(Duration::new(0, 0).saturating_sub(Duration::new(0, 1)), Duration::ZERO);
 546     /// ```
 547     #[unstable(feature = "duration_saturating_ops", issue = "76416")]
 548     #[inline]
 549     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 550     pub const fn saturating_sub(self, rhs: Duration) -> Duration {
 551         match self.checked_sub(rhs) {
 552             Some(res) => res,
 553             None => Duration::ZERO,
 554         }
 555     }
 556
 557     /// Checked `Duration` multiplication. Computes `self * other`, returning
 558     /// [`None`] if overflow occurred.
 559     ///
 560     /// # Examples
 561     ///
 562     /// Basic usage:
 563     ///
 564     /// ```
 565     /// use std::time::Duration;
 566     ///
 567     /// assert_eq!(Duration::new(0, 500_000_001).checked_mul(2), Some(Duration::new(1, 2)));
 568     /// assert_eq!(Duration::new(u64::MAX - 1, 0).checked_mul(2), None);
 569     /// ```
 570     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 571     #[inline]
 572     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 573     pub const fn checked_mul(self, rhs: u32) -> Option<Duration> {
 574         // Multiply nanoseconds as u64, because it cannot overflow that way.
 575         let total_nanos = self.nanos as u64 * rhs as u64;
 576         let extra_secs = total_nanos / (NANOS_PER_SEC as u64);
 577         let nanos = (total_nanos % (NANOS_PER_SEC as u64)) as u32;
 578         if let Some(s) = self.secs.checked_mul(rhs as u64) {
 579             if let Some(secs) = s.checked_add(extra_secs) {
 580                 debug_assert!(nanos < NANOS_PER_SEC);
 581                 return Some(Duration { secs, nanos });
 582             }
 583         }
 584         None
 585     }
 586
 587     /// Saturating `Duration` multiplication. Computes `self * other`, returning
 588     /// [`Duration::MAX`] if overflow occurred.
 589     ///
 590     /// # Examples
 591     ///
 592     /// ```
 593     /// #![feature(duration_saturating_ops)]
 594     /// #![feature(duration_constants)]
 595     /// use std::time::Duration;
 596     ///
 597     /// assert_eq!(Duration::new(0, 500_000_001).saturating_mul(2), Duration::new(1, 2));
 598     /// assert_eq!(Duration::new(u64::MAX - 1, 0).saturating_mul(2), Duration::MAX);
 599     /// ```
 600     #[unstable(feature = "duration_saturating_ops", issue = "76416")]
 601     #[inline]
 602     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 603     pub const fn saturating_mul(self, rhs: u32) -> Duration {
 604         match self.checked_mul(rhs) {
 605             Some(res) => res,
 606             None => Duration::MAX,
 607         }
 608     }
 609
 610     /// Checked `Duration` division. Computes `self / other`, returning [`None`]
 611     /// if `other == 0`.
 612     ///
 613     /// # Examples
 614     ///
 615     /// Basic usage:
 616     ///
 617     /// ```
 618     /// use std::time::Duration;
 619     ///
 620     /// assert_eq!(Duration::new(2, 0).checked_div(2), Some(Duration::new(1, 0)));
 621     /// assert_eq!(Duration::new(1, 0).checked_div(2), Some(Duration::new(0, 500_000_000)));
 622     /// assert_eq!(Duration::new(2, 0).checked_div(0), None);
 623     /// ```
 624     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 625     #[inline]
 626     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 627     pub const fn checked_div(self, rhs: u32) -> Option<Duration> {
 628         if rhs != 0 {
 629             let secs = self.secs / (rhs as u64);
 630             let carry = self.secs - secs * (rhs as u64);
 631             let extra_nanos = carry * (NANOS_PER_SEC as u64) / (rhs as u64);
 632             let nanos = self.nanos / rhs + (extra_nanos as u32);
 633             debug_assert!(nanos < NANOS_PER_SEC);
 634             Some(Duration { secs, nanos })
 635         } else {
 636             None
 637         }
 638     }
 639
 640     /// Returns the number of seconds contained by this `Duration` as `f64`.
 641     ///
 642     /// The returned value does include the fractional (nanosecond) part of the duration.
 643     ///
 644     /// # Examples
 645     /// ```
 646     /// use std::time::Duration;
 647     ///
 648     /// let dur = Duration::new(2, 700_000_000);
 649     /// assert_eq!(dur.as_secs_f64(), 2.7);
 650     /// ```
 651     #[stable(feature = "duration_float", since = "1.38.0")]
 652     #[inline]
 653     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 654     pub const fn as_secs_f64(&self) -> f64 {
 655         (self.secs as f64) + (self.nanos as f64) / (NANOS_PER_SEC as f64)
 656     }
 657
 658     /// Returns the number of seconds contained by this `Duration` as `f32`.
 659     ///
 660     /// The returned value does include the fractional (nanosecond) part of the duration.
 661     ///
 662     /// # Examples
 663     /// ```
 664     /// use std::time::Duration;
 665     ///
 666     /// let dur = Duration::new(2, 700_000_000);
 667     /// assert_eq!(dur.as_secs_f32(), 2.7);
 668     /// ```
 669     #[stable(feature = "duration_float", since = "1.38.0")]
 670     #[inline]
 671     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 672     pub const fn as_secs_f32(&self) -> f32 {
 673         (self.secs as f32) + (self.nanos as f32) / (NANOS_PER_SEC as f32)
 674     }
 675
 676     /// Creates a new `Duration` from the specified number of seconds represented
 677     /// as `f64`.
 678     ///
 679     /// # Panics
 680     /// This constructor will panic if `secs` is not finite, negative or overflows `Duration`.
 681     ///
 682     /// # Examples
 683     /// ```
 684     /// use std::time::Duration;
 685     ///
 686     /// let dur = Duration::from_secs_f64(2.7);
 687     /// assert_eq!(dur, Duration::new(2, 700_000_000));
 688     /// ```
 689     #[stable(feature = "duration_float", since = "1.38.0")]
 690     #[inline]
 691     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 692     pub const fn from_secs_f64(secs: f64) -> Duration {
 693         const MAX_NANOS_F64: f64 = ((u64::MAX as u128 + 1) * (NANOS_PER_SEC as u128)) as f64;
 694         let nanos = secs * (NANOS_PER_SEC as f64);
 695         if !nanos.is_finite() {
 696             panic!("got non-finite value when converting float to duration");
 697         }
 698         if nanos >= MAX_NANOS_F64 {
 699             panic!("overflow when converting float to duration");
 700         }
 701         if nanos < 0.0 {
 702             panic!("underflow when converting float to duration");
 703         }
 704         let nanos = nanos as u128;
 705         Duration {
 706             secs: (nanos / (NANOS_PER_SEC as u128)) as u64,
 707             nanos: (nanos % (NANOS_PER_SEC as u128)) as u32,
 708         }
 709     }
 710
 711     /// Creates a new `Duration` from the specified number of seconds represented
 712     /// as `f32`.
 713     ///
 714     /// # Panics
 715     /// This constructor will panic if `secs` is not finite, negative or overflows `Duration`.
 716     ///
 717     /// # Examples
 718     /// ```
 719     /// use std::time::Duration;
 720     ///
 721     /// let dur = Duration::from_secs_f32(2.7);
 722     /// assert_eq!(dur, Duration::new(2, 700_000_000));
 723     /// ```
 724     #[stable(feature = "duration_float", since = "1.38.0")]
 725     #[inline]
 726     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 727     pub const fn from_secs_f32(secs: f32) -> Duration {
 728         const MAX_NANOS_F32: f32 = ((u64::MAX as u128 + 1) * (NANOS_PER_SEC as u128)) as f32;
 729         let nanos = secs * (NANOS_PER_SEC as f32);
 730         if !nanos.is_finite() {
 731             panic!("got non-finite value when converting float to duration");
 732         }
 733         if nanos >= MAX_NANOS_F32 {
 734             panic!("overflow when converting float to duration");
 735         }
 736         if nanos < 0.0 {
 737             panic!("underflow when converting float to duration");
 738         }
 739         let nanos = nanos as u128;
 740         Duration {
 741             secs: (nanos / (NANOS_PER_SEC as u128)) as u64,
 742             nanos: (nanos % (NANOS_PER_SEC as u128)) as u32,
 743         }
 744     }
 745
 746     /// Multiplies `Duration` by `f64`.
 747     ///
 748     /// # Panics
 749     /// This method will panic if result is not finite, negative or overflows `Duration`.
 750     ///
 751     /// # Examples
 752     /// ```
 753     /// use std::time::Duration;
 754     ///
 755     /// let dur = Duration::new(2, 700_000_000);
 756     /// assert_eq!(dur.mul_f64(3.14), Duration::new(8, 478_000_000));
 757     /// assert_eq!(dur.mul_f64(3.14e5), Duration::new(847_800, 0));
 758     /// ```
 759     #[stable(feature = "duration_float", since = "1.38.0")]
 760     #[inline]
 761     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 762     pub const fn mul_f64(self, rhs: f64) -> Duration {
 763         Duration::from_secs_f64(rhs * self.as_secs_f64())
 764     }
 765
 766     /// Multiplies `Duration` by `f32`.
 767     ///
 768     /// # Panics
 769     /// This method will panic if result is not finite, negative or overflows `Duration`.
 770     ///
 771     /// # Examples
 772     /// ```
 773     /// use std::time::Duration;
 774     ///
 775     /// let dur = Duration::new(2, 700_000_000);
 776     /// // note that due to rounding errors result is slightly different
 777     /// // from 8.478 and 847800.0
 778     /// assert_eq!(dur.mul_f32(3.14), Duration::new(8, 478_000_640));
 779     /// assert_eq!(dur.mul_f32(3.14e5), Duration::new(847799, 969_120_256));
 780     /// ```
 781     #[stable(feature = "duration_float", since = "1.38.0")]
 782     #[inline]
 783     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 784     pub const fn mul_f32(self, rhs: f32) -> Duration {
 785         Duration::from_secs_f32(rhs * self.as_secs_f32())
 786     }
 787
 788     /// Divide `Duration` by `f64`.
 789     ///
 790     /// # Panics
 791     /// This method will panic if result is not finite, negative or overflows `Duration`.
 792     ///
 793     /// # Examples
 794     /// ```
 795     /// use std::time::Duration;
 796     ///
 797     /// let dur = Duration::new(2, 700_000_000);
 798     /// assert_eq!(dur.div_f64(3.14), Duration::new(0, 859_872_611));
 799     /// // note that truncation is used, not rounding
 800     /// assert_eq!(dur.div_f64(3.14e5), Duration::new(0, 8_598));
 801     /// ```
 802     #[stable(feature = "duration_float", since = "1.38.0")]
 803     #[inline]
 804     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 805     pub const fn div_f64(self, rhs: f64) -> Duration {
 806         Duration::from_secs_f64(self.as_secs_f64() / rhs)
 807     }
 808
 809     /// Divide `Duration` by `f32`.
 810     ///
 811     /// # Panics
 812     /// This method will panic if result is not finite, negative or overflows `Duration`.
 813     ///
 814     /// # Examples
 815     /// ```
 816     /// use std::time::Duration;
 817     ///
 818     /// let dur = Duration::new(2, 700_000_000);
 819     /// // note that due to rounding errors result is slightly
 820     /// // different from 0.859_872_611
 821     /// assert_eq!(dur.div_f32(3.14), Duration::new(0, 859_872_576));
 822     /// // note that truncation is used, not rounding
 823     /// assert_eq!(dur.div_f32(3.14e5), Duration::new(0, 8_598));
 824     /// ```
 825     #[stable(feature = "duration_float", since = "1.38.0")]
 826     #[inline]
 827     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 828     pub const fn div_f32(self, rhs: f32) -> Duration {
 829         Duration::from_secs_f32(self.as_secs_f32() / rhs)
 830     }
 831
 832     /// Divide `Duration` by `Duration` and return `f64`.
 833     ///
 834     /// # Examples
 835     /// ```
 836     /// #![feature(div_duration)]
 837     /// use std::time::Duration;
 838     ///
 839     /// let dur1 = Duration::new(2, 700_000_000);
 840     /// let dur2 = Duration::new(5, 400_000_000);
 841     /// assert_eq!(dur1.div_duration_f64(dur2), 0.5);
 842     /// ```
 843     #[unstable(feature = "div_duration", issue = "63139")]
 844     #[inline]
 845     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 846     pub const fn div_duration_f64(self, rhs: Duration) -> f64 {
 847         self.as_secs_f64() / rhs.as_secs_f64()
 848     }
 849
 850     /// Divide `Duration` by `Duration` and return `f32`.
 851     ///
 852     /// # Examples
 853     /// ```
 854     /// #![feature(div_duration)]
 855     /// use std::time::Duration;
 856     ///
 857     /// let dur1 = Duration::new(2, 700_000_000);
 858     /// let dur2 = Duration::new(5, 400_000_000);
 859     /// assert_eq!(dur1.div_duration_f32(dur2), 0.5);
 860     /// ```
 861     #[unstable(feature = "div_duration", issue = "63139")]
 862     #[inline]
 863     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 864     pub const fn div_duration_f32(self, rhs: Duration) -> f32 {
 865         self.as_secs_f32() / rhs.as_secs_f32()
 866     }
 867 }
 868
 869 #[stable(feature = "duration", since = "1.3.0")]
 870 impl Add for Duration {
 871     type Output = Duration;
 872
 873     fn add(self, rhs: Duration) -> Duration {
 874         self.checked_add(rhs).expect("overflow when adding durations")
 875     }
 876 }
 877
 878 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 879 impl AddAssign for Duration {
 880     fn add_assign(&mut self, rhs: Duration) {
 881         *self = *self + rhs;
 882     }
 883 }
 884
 885 #[stable(feature = "duration", since = "1.3.0")]
 886 impl Sub for Duration {
 887     type Output = Duration;
 888
 889     fn sub(self, rhs: Duration) -> Duration {
 890         self.checked_sub(rhs).expect("overflow when subtracting durations")
 891     }
 892 }
 893
 894 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 895 impl SubAssign for Duration {
 896     fn sub_assign(&mut self, rhs: Duration) {
 897         *self = *self - rhs;
 898     }
 899 }
 900
 901 #[stable(feature = "duration", since = "1.3.0")]
 902 impl Mul<u32> for Duration {
 903     type Output = Duration;
 904
 905     fn mul(self, rhs: u32) -> Duration {
 906         self.checked_mul(rhs).expect("overflow when multiplying duration by scalar")
 907     }
 908 }
 909
 910 #[stable(feature = "symmetric_u32_duration_mul", since = "1.31.0")]
 911 impl Mul<Duration> for u32 {
 912     type Output = Duration;
 913
 914     fn mul(self, rhs: Duration) -> Duration {
 915         rhs * self
 916     }
 917 }
 918
 919 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 920 impl MulAssign<u32> for Duration {
 921     fn mul_assign(&mut self, rhs: u32) {
 922         *self = *self * rhs;
 923     }
 924 }
 925
 926 #[stable(feature = "duration", since = "1.3.0")]
 927 impl Div<u32> for Duration {
 928     type Output = Duration;
 929
 930     fn div(self, rhs: u32) -> Duration {
 931         self.checked_div(rhs).expect("divide by zero error when dividing duration by scalar")
 932     }
 933 }
 934
 935 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 936 impl DivAssign<u32> for Duration {
 937     fn div_assign(&mut self, rhs: u32) {
 938         *self = *self / rhs;
 939     }
 940 }
 941
 942 macro_rules! sum_durations {
 943     ($iter:expr) => {{
 944         let mut total_secs: u64 = 0;
 945         let mut total_nanos: u64 = 0;
 946
 947         for entry in $iter {
 948             total_secs =
 949                 total_secs.checked_add(entry.secs).expect("overflow in iter::sum over durations");
 950             total_nanos = match total_nanos.checked_add(entry.nanos as u64) {
 951                 Some(n) => n,
 952                 None => {
 953                     total_secs = total_secs
 954                         .checked_add(total_nanos / NANOS_PER_SEC as u64)
 955                         .expect("overflow in iter::sum over durations");
 956                     (total_nanos % NANOS_PER_SEC as u64) + entry.nanos as u64
 957                 }
 958             };
 959         }
 960         total_secs = total_secs
 961             .checked_add(total_nanos / NANOS_PER_SEC as u64)
 962             .expect("overflow in iter::sum over durations");
 963         total_nanos = total_nanos % NANOS_PER_SEC as u64;
 964         Duration { secs: total_secs, nanos: total_nanos as u32 }
 965     }};
 966 }
 967
 968 #[stable(feature = "duration_sum", since = "1.16.0")]
 969 impl Sum for Duration {
 970     fn sum<I: Iterator<Item = Duration>>(iter: I) -> Duration {
 971         sum_durations!(iter)
 972     }
 973 }
 974
 975 #[stable(feature = "duration_sum", since = "1.16.0")]
 976 impl<'a> Sum<&'a Duration> for Duration {
 977     fn sum<I: Iterator<Item = &'a Duration>>(iter: I) -> Duration {
 978         sum_durations!(iter)
 979     }
 980 }
 981
 982 #[stable(feature = "duration_debug_impl", since = "1.27.0")]
 983 impl fmt::Debug for Duration {
 984     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 985         /// Formats a floating point number in decimal notation.
 986         ///
 987         /// The number is given as the `integer_part` and a fractional part.
 988         /// The value of the fractional part is `fractional_part / divisor`. So
 989         /// `integer_part` = 3, `fractional_part` = 12 and `divisor` = 100
 990         /// represents the number `3.012`. Trailing zeros are omitted.
 991         ///
 992         /// `divisor` must not be above 100_000_000. It also should be a power
 993         /// of 10, everything else doesn't make sense. `fractional_part` has
 994         /// to be less than `10 * divisor`!
 995         fn fmt_decimal(
 996             f: &mut fmt::Formatter<'_>,
 997             mut integer_part: u64,
 998             mut fractional_part: u32,
 999             mut divisor: u32,
1000         ) -> fmt::Result {
1001             // Encode the fractional part into a temporary buffer. The buffer
1002             // only need to hold 9 elements, because `fractional_part` has to
1003             // be smaller than 10^9. The buffer is prefilled with '0' digits
1004             // to simplify the code below.
1005             let mut buf = [b'0'; 9];
1006
1007             // The next digit is written at this position
1008             let mut pos = 0;
1009
1010             // We keep writing digits into the buffer while there are non-zero
1011             // digits left and we haven't written enough digits yet.
1012             while fractional_part > 0 && pos < f.precision().unwrap_or(9) {
1013                 // Write new digit into the buffer
1014                 buf[pos] = b'0' + (fractional_part / divisor) as u8;
1015
1016                 fractional_part %= divisor;
1017                 divisor /= 10;
1018                 pos += 1;
1019             }
1020
1021             // If a precision < 9 was specified, there may be some non-zero
1022             // digits left that weren't written into the buffer. In that case we
1023             // need to perform rounding to match the semantics of printing
1024             // normal floating point numbers. However, we only need to do work
1025             // when rounding up. This happens if the first digit of the
1026             // remaining ones is >= 5.
1027             if fractional_part > 0 && fractional_part >= divisor * 5 {
1028                 // Round up the number contained in the buffer. We go through
1029                 // the buffer backwards and keep track of the carry.
1030                 let mut rev_pos = pos;
1031                 let mut carry = true;
1032                 while carry && rev_pos > 0 {
1033                     rev_pos -= 1;
1034
1035                     // If the digit in the buffer is not '9', we just need to
1036                     // increment it and can stop then (since we don't have a
1037                     // carry anymore). Otherwise, we set it to '0' (overflow)
1038                     // and continue.
1039                     if buf[rev_pos] < b'9' {
1040                         buf[rev_pos] += 1;
1041                         carry = false;
1042                     } else {
1043                         buf[rev_pos] = b'0';
1044                     }
1045                 }
1046
1047                 // If we still have the carry bit set, that means that we set
1048                 // the whole buffer to '0's and need to increment the integer
1049                 // part.
1050                 if carry {
1051                     integer_part += 1;
1052                 }
1053             }
1054
1055             // Determine the end of the buffer: if precision is set, we just
1056             // use as many digits from the buffer (capped to 9). If it isn't
1057             // set, we only use all digits up to the last non-zero one.
1058             let end = f.precision().map(|p| crate::cmp::min(p, 9)).unwrap_or(pos);
1059
1060             // If we haven't emitted a single fractional digit and the precision
1061             // wasn't set to a non-zero value, we don't print the decimal point.
1062             if end == 0 {
1063                 write!(f, "{}", integer_part)
1064             } else {
1065                 // SAFETY: We are only writing ASCII digits into the buffer and it was
1066                 // initialized with '0's, so it contains valid UTF8.
1067                 let s = unsafe { crate::str::from_utf8_unchecked(&buf[..end]) };
1068
1069                 // If the user request a precision > 9, we pad '0's at the end.
1070                 let w = f.precision().unwrap_or(pos);
1071                 write!(f, "{}.{:0<width$}", integer_part, s, width = w)
1072             }
1073         }
1074
1075         // Print leading '+' sign if requested
1076         if f.sign_plus() {
1077             write!(f, "+")?;
1078         }
1079
1080         if self.secs > 0 {
1081             fmt_decimal(f, self.secs, self.nanos, NANOS_PER_SEC / 10)?;
1082             f.write_str("s")
1083         } else if self.nanos >= NANOS_PER_MILLI {
1084             fmt_decimal(
1085                 f,
1086                 (self.nanos / NANOS_PER_MILLI) as u64,
1087                 self.nanos % NANOS_PER_MILLI,
1088                 NANOS_PER_MILLI / 10,
1089             )?;
1090             f.write_str("ms")
1091         } else if self.nanos >= NANOS_PER_MICRO {
1092             fmt_decimal(
1093                 f,
1094                 (self.nanos / NANOS_PER_MICRO) as u64,
1095                 self.nanos % NANOS_PER_MICRO,
1096                 NANOS_PER_MICRO / 10,
1097             )?;
1098             f.write_str("µs")
1099         } else {
1100             fmt_decimal(f, self.nanos as u64, 0, 1)?;
1101             f.write_str("ns")
1102         }
1103     }
1104 }