library/core/src/time.rs

   1 #![stable(feature = "duration_core", since = "1.25.0")]
   2
   3 //! Temporal quantification.
   4 //!
   5 //! # Examples:
   6 //!
   7 //! There are multiple ways to create a new [`Duration`]:
   8 //!
   9 //! ```
  10 //! # use std::time::Duration;
  11 //! let five_seconds = Duration::from_secs(5);
  12 //! assert_eq!(five_seconds, Duration::from_millis(5_000));
  13 //! assert_eq!(five_seconds, Duration::from_micros(5_000_000));
  14 //! assert_eq!(five_seconds, Duration::from_nanos(5_000_000_000));
  15 //!
  16 //! let ten_seconds = Duration::from_secs(10);
  17 //! let seven_nanos = Duration::from_nanos(7);
  18 //! let total = ten_seconds + seven_nanos;
  19 //! assert_eq!(total, Duration::new(10, 7));
  20 //! ```
  21
  22 use crate::fmt;
  23 use crate::iter::Sum;
  24 use crate::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
  25
  26 const NANOS_PER_SEC: u32 = 1_000_000_000;
  27 const NANOS_PER_MILLI: u32 = 1_000_000;
  28 const NANOS_PER_MICRO: u32 = 1_000;
  29 const MILLIS_PER_SEC: u64 = 1_000;
  30 const MICROS_PER_SEC: u64 = 1_000_000;
  31
  32 /// A `Duration` type to represent a span of time, typically used for system
  33 /// timeouts.
  34 ///
  35 /// Each `Duration` is composed of a whole number of seconds and a fractional part
  36 /// represented in nanoseconds. If the underlying system does not support
  37 /// nanosecond-level precision, APIs binding a system timeout will typically round up
  38 /// the number of nanoseconds.
  39 ///
  40 /// [`Duration`]s implement many common traits, including [`Add`], [`Sub`], and other
  41 /// [`ops`] traits. It implements [`Default`] by returning a zero-length `Duration`.
  42 ///
  43 /// [`ops`]: crate::ops
  44 ///
  45 /// # Examples
  46 ///
  47 /// ```
  48 /// use std::time::Duration;
  49 ///
  50 /// let five_seconds = Duration::new(5, 0);
  51 /// let five_seconds_and_five_nanos = five_seconds + Duration::new(0, 5);
  52 ///
  53 /// assert_eq!(five_seconds_and_five_nanos.as_secs(), 5);
  54 /// assert_eq!(five_seconds_and_five_nanos.subsec_nanos(), 5);
  55 ///
  56 /// let ten_millis = Duration::from_millis(10);
  57 /// ```
  58 ///
  59 /// # Formatting `Duration` values
  60 ///
  61 /// `Duration` intentionally does not have a `Display` impl, as there are a
  62 /// variety of ways to format spans of time for human readability. `Duration`
  63 /// provides a `Debug` impl that shows the full precision of the value.
  64 ///
  65 /// The `Debug` output uses the non-ASCII "µs" suffix for microseconds. If your
  66 /// program output may appear in contexts that cannot rely on full Unicode
  67 /// compatibility, you may wish to format `Duration` objects yourself or use a
  68 /// crate to do so.
  69 #[stable(feature = "duration", since = "1.3.0")]
  70 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
  71 #[cfg_attr(not(test), rustc_diagnostic_item = "Duration")]
  72 pub struct Duration {
  73     secs: u64,
  74     nanos: u32, // Always 0 <= nanos < NANOS_PER_SEC
  75 }
  76
  77 impl Duration {
  78     /// The duration of one second.
  79     ///
  80     /// # Examples
  81     ///
  82     /// ```
  83     /// #![feature(duration_constants)]
  84     /// use std::time::Duration;
  85     ///
  86     /// assert_eq!(Duration::SECOND, Duration::from_secs(1));
  87     /// ```
  88     #[unstable(feature = "duration_constants", issue = "57391")]
  89     pub const SECOND: Duration = Duration::from_secs(1);
  90
  91     /// The duration of one millisecond.
  92     ///
  93     /// # Examples
  94     ///
  95     /// ```
  96     /// #![feature(duration_constants)]
  97     /// use std::time::Duration;
  98     ///
  99     /// assert_eq!(Duration::MILLISECOND, Duration::from_millis(1));
 100     /// ```
 101     #[unstable(feature = "duration_constants", issue = "57391")]
 102     pub const MILLISECOND: Duration = Duration::from_millis(1);
 103
 104     /// The duration of one microsecond.
 105     ///
 106     /// # Examples
 107     ///
 108     /// ```
 109     /// #![feature(duration_constants)]
 110     /// use std::time::Duration;
 111     ///
 112     /// assert_eq!(Duration::MICROSECOND, Duration::from_micros(1));
 113     /// ```
 114     #[unstable(feature = "duration_constants", issue = "57391")]
 115     pub const MICROSECOND: Duration = Duration::from_micros(1);
 116
 117     /// The duration of one nanosecond.
 118     ///
 119     /// # Examples
 120     ///
 121     /// ```
 122     /// #![feature(duration_constants)]
 123     /// use std::time::Duration;
 124     ///
 125     /// assert_eq!(Duration::NANOSECOND, Duration::from_nanos(1));
 126     /// ```
 127     #[unstable(feature = "duration_constants", issue = "57391")]
 128     pub const NANOSECOND: Duration = Duration::from_nanos(1);
 129
 130     /// A duration of zero time.
 131     ///
 132     /// # Examples
 133     ///
 134     /// ```
 135     /// use std::time::Duration;
 136     ///
 137     /// let duration = Duration::ZERO;
 138     /// assert!(duration.is_zero());
 139     /// assert_eq!(duration.as_nanos(), 0);
 140     /// ```
 141     #[stable(feature = "duration_zero", since = "1.53.0")]
 142     pub const ZERO: Duration = Duration::from_nanos(0);
 143
 144     /// The maximum duration.
 145     ///
 146     /// May vary by platform as necessary. Must be able to contain the difference between
 147     /// two instances of [`Instant`] or two instances of [`SystemTime`].
 148     /// This constraint gives it a value of about 584,942,417,355 years in practice,
 149     /// which is currently used on all platforms.
 150     ///
 151     /// # Examples
 152     ///
 153     /// ```
 154     /// use std::time::Duration;
 155     ///
 156     /// assert_eq!(Duration::MAX, Duration::new(u64::MAX, 1_000_000_000 - 1));
 157     /// ```
 158     /// [`Instant`]: ../../std/time/struct.Instant.html
 159     /// [`SystemTime`]: ../../std/time/struct.SystemTime.html
 160     #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
 161     pub const MAX: Duration = Duration::new(u64::MAX, NANOS_PER_SEC - 1);
 162
 163     /// Creates a new `Duration` from the specified number of whole seconds and
 164     /// additional nanoseconds.
 165     ///
 166     /// If the number of nanoseconds is greater than 1 billion (the number of
 167     /// nanoseconds in a second), then it will carry over into the seconds provided.
 168     ///
 169     /// # Panics
 170     ///
 171     /// This constructor will panic if the carry from the nanoseconds overflows
 172     /// the seconds counter.
 173     ///
 174     /// # Examples
 175     ///
 176     /// ```
 177     /// use std::time::Duration;
 178     ///
 179     /// let five_seconds = Duration::new(5, 0);
 180     /// ```
 181     #[stable(feature = "duration", since = "1.3.0")]
 182     #[inline]
 183     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 184     pub const fn new(secs: u64, nanos: u32) -> Duration {
 185         let secs = match secs.checked_add((nanos / NANOS_PER_SEC) as u64) {
 186             Some(secs) => secs,
 187             None => panic!("overflow in Duration::new"),
 188         };
 189         let nanos = nanos % NANOS_PER_SEC;
 190         Duration { secs, nanos }
 191     }
 192
 193     /// Creates a new `Duration` from the specified number of whole seconds.
 194     ///
 195     /// # Examples
 196     ///
 197     /// ```
 198     /// use std::time::Duration;
 199     ///
 200     /// let duration = Duration::from_secs(5);
 201     ///
 202     /// assert_eq!(5, duration.as_secs());
 203     /// assert_eq!(0, duration.subsec_nanos());
 204     /// ```
 205     #[stable(feature = "duration", since = "1.3.0")]
 206     #[inline]
 207     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 208     pub const fn from_secs(secs: u64) -> Duration {
 209         Duration { secs, nanos: 0 }
 210     }
 211
 212     /// Creates a new `Duration` from the specified number of milliseconds.
 213     ///
 214     /// # Examples
 215     ///
 216     /// ```
 217     /// use std::time::Duration;
 218     ///
 219     /// let duration = Duration::from_millis(2569);
 220     ///
 221     /// assert_eq!(2, duration.as_secs());
 222     /// assert_eq!(569_000_000, duration.subsec_nanos());
 223     /// ```
 224     #[stable(feature = "duration", since = "1.3.0")]
 225     #[inline]
 226     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 227     pub const fn from_millis(millis: u64) -> Duration {
 228         Duration {
 229             secs: millis / MILLIS_PER_SEC,
 230             nanos: ((millis % MILLIS_PER_SEC) as u32) * NANOS_PER_MILLI,
 231         }
 232     }
 233
 234     /// Creates a new `Duration` from the specified number of microseconds.
 235     ///
 236     /// # Examples
 237     ///
 238     /// ```
 239     /// use std::time::Duration;
 240     ///
 241     /// let duration = Duration::from_micros(1_000_002);
 242     ///
 243     /// assert_eq!(1, duration.as_secs());
 244     /// assert_eq!(2000, duration.subsec_nanos());
 245     /// ```
 246     #[stable(feature = "duration_from_micros", since = "1.27.0")]
 247     #[inline]
 248     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 249     pub const fn from_micros(micros: u64) -> Duration {
 250         Duration {
 251             secs: micros / MICROS_PER_SEC,
 252             nanos: ((micros % MICROS_PER_SEC) as u32) * NANOS_PER_MICRO,
 253         }
 254     }
 255
 256     /// Creates a new `Duration` from the specified number of nanoseconds.
 257     ///
 258     /// # Examples
 259     ///
 260     /// ```
 261     /// use std::time::Duration;
 262     ///
 263     /// let duration = Duration::from_nanos(1_000_000_123);
 264     ///
 265     /// assert_eq!(1, duration.as_secs());
 266     /// assert_eq!(123, duration.subsec_nanos());
 267     /// ```
 268     #[stable(feature = "duration_extras", since = "1.27.0")]
 269     #[inline]
 270     #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
 271     pub const fn from_nanos(nanos: u64) -> Duration {
 272         Duration {
 273             secs: nanos / (NANOS_PER_SEC as u64),
 274             nanos: (nanos % (NANOS_PER_SEC as u64)) as u32,
 275         }
 276     }
 277
 278     /// Returns true if this `Duration` spans no time.
 279     ///
 280     /// # Examples
 281     ///
 282     /// ```
 283     /// use std::time::Duration;
 284     ///
 285     /// assert!(Duration::ZERO.is_zero());
 286     /// assert!(Duration::new(0, 0).is_zero());
 287     /// assert!(Duration::from_nanos(0).is_zero());
 288     /// assert!(Duration::from_secs(0).is_zero());
 289     ///
 290     /// assert!(!Duration::new(1, 1).is_zero());
 291     /// assert!(!Duration::from_nanos(1).is_zero());
 292     /// assert!(!Duration::from_secs(1).is_zero());
 293     /// ```
 294     #[stable(feature = "duration_zero", since = "1.53.0")]
 295     #[rustc_const_stable(feature = "duration_zero", since = "1.53.0")]
 296     #[inline]
 297     pub const fn is_zero(&self) -> bool {
 298         self.secs == 0 && self.nanos == 0
 299     }
 300
 301     /// Returns the number of _whole_ seconds contained by this `Duration`.
 302     ///
 303     /// The returned value does not include the fractional (nanosecond) part of the
 304     /// duration, which can be obtained using [`subsec_nanos`].
 305     ///
 306     /// # Examples
 307     ///
 308     /// ```
 309     /// use std::time::Duration;
 310     ///
 311     /// let duration = Duration::new(5, 730023852);
 312     /// assert_eq!(duration.as_secs(), 5);
 313     /// ```
 314     ///
 315     /// To determine the total number of seconds represented by the `Duration`,
 316     /// use `as_secs` in combination with [`subsec_nanos`]:
 317     ///
 318     /// ```
 319     /// use std::time::Duration;
 320     ///
 321     /// let duration = Duration::new(5, 730023852);
 322     ///
 323     /// assert_eq!(5.730023852,
 324     ///            duration.as_secs() as f64
 325     ///            + duration.subsec_nanos() as f64 * 1e-9);
 326     /// ```
 327     ///
 328     /// [`subsec_nanos`]: Duration::subsec_nanos
 329     #[stable(feature = "duration", since = "1.3.0")]
 330     #[rustc_const_stable(feature = "duration", since = "1.32.0")]
 331     #[inline]
 332     pub const fn as_secs(&self) -> u64 {
 333         self.secs
 334     }
 335
 336     /// Returns the fractional part of this `Duration`, in whole milliseconds.
 337     ///
 338     /// This method does **not** return the length of the duration when
 339     /// represented by milliseconds. The returned number always represents a
 340     /// fractional portion of a second (i.e., it is less than one thousand).
 341     ///
 342     /// # Examples
 343     ///
 344     /// ```
 345     /// use std::time::Duration;
 346     ///
 347     /// let duration = Duration::from_millis(5432);
 348     /// assert_eq!(duration.as_secs(), 5);
 349     /// assert_eq!(duration.subsec_millis(), 432);
 350     /// ```
 351     #[stable(feature = "duration_extras", since = "1.27.0")]
 352     #[rustc_const_stable(feature = "duration_extras", since = "1.32.0")]
 353     #[inline]
 354     pub const fn subsec_millis(&self) -> u32 {
 355         self.nanos / NANOS_PER_MILLI
 356     }
 357
 358     /// Returns the fractional part of this `Duration`, in whole microseconds.
 359     ///
 360     /// This method does **not** return the length of the duration when
 361     /// represented by microseconds. The returned number always represents a
 362     /// fractional portion of a second (i.e., it is less than one million).
 363     ///
 364     /// # Examples
 365     ///
 366     /// ```
 367     /// use std::time::Duration;
 368     ///
 369     /// let duration = Duration::from_micros(1_234_567);
 370     /// assert_eq!(duration.as_secs(), 1);
 371     /// assert_eq!(duration.subsec_micros(), 234_567);
 372     /// ```
 373     #[stable(feature = "duration_extras", since = "1.27.0")]
 374     #[rustc_const_stable(feature = "duration_extras", since = "1.32.0")]
 375     #[inline]
 376     pub const fn subsec_micros(&self) -> u32 {
 377         self.nanos / NANOS_PER_MICRO
 378     }
 379
 380     /// Returns the fractional part of this `Duration`, in nanoseconds.
 381     ///
 382     /// This method does **not** return the length of the duration when
 383     /// represented by nanoseconds. The returned number always represents a
 384     /// fractional portion of a second (i.e., it is less than one billion).
 385     ///
 386     /// # Examples
 387     ///
 388     /// ```
 389     /// use std::time::Duration;
 390     ///
 391     /// let duration = Duration::from_millis(5010);
 392     /// assert_eq!(duration.as_secs(), 5);
 393     /// assert_eq!(duration.subsec_nanos(), 10_000_000);
 394     /// ```
 395     #[stable(feature = "duration", since = "1.3.0")]
 396     #[rustc_const_stable(feature = "duration", since = "1.32.0")]
 397     #[inline]
 398     pub const fn subsec_nanos(&self) -> u32 {
 399         self.nanos
 400     }
 401
 402     /// Returns the total number of whole milliseconds contained by this `Duration`.
 403     ///
 404     /// # Examples
 405     ///
 406     /// ```
 407     /// use std::time::Duration;
 408     ///
 409     /// let duration = Duration::new(5, 730023852);
 410     /// assert_eq!(duration.as_millis(), 5730);
 411     /// ```
 412     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 413     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 414     #[inline]
 415     pub const fn as_millis(&self) -> u128 {
 416         self.secs as u128 * MILLIS_PER_SEC as u128 + (self.nanos / NANOS_PER_MILLI) as u128
 417     }
 418
 419     /// Returns the total number of whole microseconds contained by this `Duration`.
 420     ///
 421     /// # Examples
 422     ///
 423     /// ```
 424     /// use std::time::Duration;
 425     ///
 426     /// let duration = Duration::new(5, 730023852);
 427     /// assert_eq!(duration.as_micros(), 5730023);
 428     /// ```
 429     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 430     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 431     #[inline]
 432     pub const fn as_micros(&self) -> u128 {
 433         self.secs as u128 * MICROS_PER_SEC as u128 + (self.nanos / NANOS_PER_MICRO) as u128
 434     }
 435
 436     /// Returns the total number of nanoseconds contained by this `Duration`.
 437     ///
 438     /// # Examples
 439     ///
 440     /// ```
 441     /// use std::time::Duration;
 442     ///
 443     /// let duration = Duration::new(5, 730023852);
 444     /// assert_eq!(duration.as_nanos(), 5730023852);
 445     /// ```
 446     #[stable(feature = "duration_as_u128", since = "1.33.0")]
 447     #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
 448     #[inline]
 449     pub const fn as_nanos(&self) -> u128 {
 450         self.secs as u128 * NANOS_PER_SEC as u128 + self.nanos as u128
 451     }
 452
 453     /// Checked `Duration` addition. Computes `self + other`, returning [`None`]
 454     /// if overflow occurred.
 455     ///
 456     /// # Examples
 457     ///
 458     /// Basic usage:
 459     ///
 460     /// ```
 461     /// use std::time::Duration;
 462     ///
 463     /// assert_eq!(Duration::new(0, 0).checked_add(Duration::new(0, 1)), Some(Duration::new(0, 1)));
 464     /// assert_eq!(Duration::new(1, 0).checked_add(Duration::new(u64::MAX, 0)), None);
 465     /// ```
 466     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 467     #[inline]
 468     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 469     pub const fn checked_add(self, rhs: Duration) -> Option<Duration> {
 470         if let Some(mut secs) = self.secs.checked_add(rhs.secs) {
 471             let mut nanos = self.nanos + rhs.nanos;
 472             if nanos >= NANOS_PER_SEC {
 473                 nanos -= NANOS_PER_SEC;
 474                 if let Some(new_secs) = secs.checked_add(1) {
 475                     secs = new_secs;
 476                 } else {
 477                     return None;
 478                 }
 479             }
 480             debug_assert!(nanos < NANOS_PER_SEC);
 481             Some(Duration { secs, nanos })
 482         } else {
 483             None
 484         }
 485     }
 486
 487     /// Saturating `Duration` addition. Computes `self + other`, returning [`Duration::MAX`]
 488     /// if overflow occurred.
 489     ///
 490     /// # Examples
 491     ///
 492     /// ```
 493     /// #![feature(duration_constants)]
 494     /// use std::time::Duration;
 495     ///
 496     /// assert_eq!(Duration::new(0, 0).saturating_add(Duration::new(0, 1)), Duration::new(0, 1));
 497     /// assert_eq!(Duration::new(1, 0).saturating_add(Duration::new(u64::MAX, 0)), Duration::MAX);
 498     /// ```
 499     #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
 500     #[inline]
 501     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 502     pub const fn saturating_add(self, rhs: Duration) -> Duration {
 503         match self.checked_add(rhs) {
 504             Some(res) => res,
 505             None => Duration::MAX,
 506         }
 507     }
 508
 509     /// Checked `Duration` subtraction. Computes `self - other`, returning [`None`]
 510     /// if the result would be negative or if overflow occurred.
 511     ///
 512     /// # Examples
 513     ///
 514     /// Basic usage:
 515     ///
 516     /// ```
 517     /// use std::time::Duration;
 518     ///
 519     /// assert_eq!(Duration::new(0, 1).checked_sub(Duration::new(0, 0)), Some(Duration::new(0, 1)));
 520     /// assert_eq!(Duration::new(0, 0).checked_sub(Duration::new(0, 1)), None);
 521     /// ```
 522     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 523     #[inline]
 524     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 525     pub const fn checked_sub(self, rhs: Duration) -> Option<Duration> {
 526         if let Some(mut secs) = self.secs.checked_sub(rhs.secs) {
 527             let nanos = if self.nanos >= rhs.nanos {
 528                 self.nanos - rhs.nanos
 529             } else if let Some(sub_secs) = secs.checked_sub(1) {
 530                 secs = sub_secs;
 531                 self.nanos + NANOS_PER_SEC - rhs.nanos
 532             } else {
 533                 return None;
 534             };
 535             debug_assert!(nanos < NANOS_PER_SEC);
 536             Some(Duration { secs, nanos })
 537         } else {
 538             None
 539         }
 540     }
 541
 542     /// Saturating `Duration` subtraction. Computes `self - other`, returning [`Duration::ZERO`]
 543     /// if the result would be negative or if overflow occurred.
 544     ///
 545     /// # Examples
 546     ///
 547     /// ```
 548     /// use std::time::Duration;
 549     ///
 550     /// assert_eq!(Duration::new(0, 1).saturating_sub(Duration::new(0, 0)), Duration::new(0, 1));
 551     /// assert_eq!(Duration::new(0, 0).saturating_sub(Duration::new(0, 1)), Duration::ZERO);
 552     /// ```
 553     #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
 554     #[inline]
 555     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 556     pub const fn saturating_sub(self, rhs: Duration) -> Duration {
 557         match self.checked_sub(rhs) {
 558             Some(res) => res,
 559             None => Duration::ZERO,
 560         }
 561     }
 562
 563     /// Checked `Duration` multiplication. Computes `self * other`, returning
 564     /// [`None`] if overflow occurred.
 565     ///
 566     /// # Examples
 567     ///
 568     /// Basic usage:
 569     ///
 570     /// ```
 571     /// use std::time::Duration;
 572     ///
 573     /// assert_eq!(Duration::new(0, 500_000_001).checked_mul(2), Some(Duration::new(1, 2)));
 574     /// assert_eq!(Duration::new(u64::MAX - 1, 0).checked_mul(2), None);
 575     /// ```
 576     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
 577     #[inline]
 578     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 579     pub const fn checked_mul(self, rhs: u32) -> Option<Duration> {
 580         // Multiply nanoseconds as u64, because it cannot overflow that way.
 581         let total_nanos = self.nanos as u64 * rhs as u64;
 582         let extra_secs = total_nanos / (NANOS_PER_SEC as u64);
 583         let nanos = (total_nanos % (NANOS_PER_SEC as u64)) as u32;
 584         if let Some(s) = self.secs.checked_mul(rhs as u64) {
 585             if let Some(secs) = s.checked_add(extra_secs) {
 586                 debug_assert!(nanos < NANOS_PER_SEC);
 587                 return Some(Duration { secs, nanos });
 588             }
 589         }
 590         None
 591     }
 592
 593     /// Saturating `Duration` multiplication. Computes `self * other`, returning
 594     /// [`Duration::MAX`] if overflow occurred.
 595     ///
 596     /// # Examples
 597     ///
 598     /// ```
 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     #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
 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         match Duration::try_from_secs_f64(secs) {
 699             Ok(v) => v,
 700             Err(e) => crate::panicking::panic(e.description()),
 701         }
 702     }
 703
 704     /// The checked version of [`from_secs_f64`].
 705     ///
 706     /// [`from_secs_f64`]: Duration::from_secs_f64
 707     ///
 708     /// This constructor will return an `Err` if `secs` is not finite, negative or overflows `Duration`.
 709     ///
 710     /// # Examples
 711     /// ```
 712     /// #![feature(duration_checked_float)]
 713     ///
 714     /// use std::time::Duration;
 715     ///
 716     /// let dur = Duration::try_from_secs_f64(2.7);
 717     /// assert_eq!(dur, Ok(Duration::new(2, 700_000_000)));
 718     ///
 719     /// let negative = Duration::try_from_secs_f64(-5.0);
 720     /// assert!(negative.is_err());
 721     /// ```
 722     #[unstable(feature = "duration_checked_float", issue = "83400")]
 723     #[inline]
 724     pub const fn try_from_secs_f64(secs: f64) -> Result<Duration, FromSecsError> {
 725         const MAX_NANOS_F64: f64 = ((u64::MAX as u128 + 1) * (NANOS_PER_SEC as u128)) as f64;
 726         let nanos = secs * (NANOS_PER_SEC as f64);
 727         if !nanos.is_finite() {
 728             Err(FromSecsError { kind: FromSecsErrorKind::NonFinite })
 729         } else if nanos >= MAX_NANOS_F64 {
 730             Err(FromSecsError { kind: FromSecsErrorKind::Overflow })
 731         } else if nanos < 0.0 {
 732             Err(FromSecsError { kind: FromSecsErrorKind::Underflow })
 733         } else {
 734             let nanos = nanos as u128;
 735             Ok(Duration {
 736                 secs: (nanos / (NANOS_PER_SEC as u128)) as u64,
 737                 nanos: (nanos % (NANOS_PER_SEC as u128)) as u32,
 738             })
 739         }
 740     }
 741
 742     /// Creates a new `Duration` from the specified number of seconds represented
 743     /// as `f32`.
 744     ///
 745     /// # Panics
 746     /// This constructor will panic if `secs` is not finite, negative or overflows `Duration`.
 747     ///
 748     /// # Examples
 749     /// ```
 750     /// use std::time::Duration;
 751     ///
 752     /// let dur = Duration::from_secs_f32(2.7);
 753     /// assert_eq!(dur, Duration::new(2, 700_000_000));
 754     /// ```
 755     #[stable(feature = "duration_float", since = "1.38.0")]
 756     #[inline]
 757     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 758     pub const fn from_secs_f32(secs: f32) -> Duration {
 759         match Duration::try_from_secs_f32(secs) {
 760             Ok(v) => v,
 761             Err(e) => crate::panicking::panic(e.description()),
 762         }
 763     }
 764
 765     /// The checked version of [`from_secs_f32`].
 766     ///
 767     /// [`from_secs_f32`]: Duration::from_secs_f32
 768     ///
 769     /// This constructor will return an `Err` if `secs` is not finite, negative or overflows `Duration`.
 770     ///
 771     /// # Examples
 772     /// ```
 773     /// #![feature(duration_checked_float)]
 774     ///
 775     /// use std::time::Duration;
 776     ///
 777     /// let dur = Duration::try_from_secs_f32(2.7);
 778     /// assert_eq!(dur, Ok(Duration::new(2, 700_000_000)));
 779     ///
 780     /// let negative = Duration::try_from_secs_f32(-5.0);
 781     /// assert!(negative.is_err());
 782     /// ```
 783     #[unstable(feature = "duration_checked_float", issue = "83400")]
 784     #[inline]
 785     pub const fn try_from_secs_f32(secs: f32) -> Result<Duration, FromSecsError> {
 786         const MAX_NANOS_F32: f32 = ((u64::MAX as u128 + 1) * (NANOS_PER_SEC as u128)) as f32;
 787         let nanos = secs * (NANOS_PER_SEC as f32);
 788         if !nanos.is_finite() {
 789             Err(FromSecsError { kind: FromSecsErrorKind::NonFinite })
 790         } else if nanos >= MAX_NANOS_F32 {
 791             Err(FromSecsError { kind: FromSecsErrorKind::Overflow })
 792         } else if nanos < 0.0 {
 793             Err(FromSecsError { kind: FromSecsErrorKind::Underflow })
 794         } else {
 795             let nanos = nanos as u128;
 796             Ok(Duration {
 797                 secs: (nanos / (NANOS_PER_SEC as u128)) as u64,
 798                 nanos: (nanos % (NANOS_PER_SEC as u128)) as u32,
 799             })
 800         }
 801     }
 802
 803     /// Multiplies `Duration` by `f64`.
 804     ///
 805     /// # Panics
 806     /// This method will panic if result is not finite, negative or overflows `Duration`.
 807     ///
 808     /// # Examples
 809     /// ```
 810     /// use std::time::Duration;
 811     ///
 812     /// let dur = Duration::new(2, 700_000_000);
 813     /// assert_eq!(dur.mul_f64(3.14), Duration::new(8, 478_000_000));
 814     /// assert_eq!(dur.mul_f64(3.14e5), Duration::new(847_800, 0));
 815     /// ```
 816     #[stable(feature = "duration_float", since = "1.38.0")]
 817     #[inline]
 818     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 819     pub const fn mul_f64(self, rhs: f64) -> Duration {
 820         Duration::from_secs_f64(rhs * self.as_secs_f64())
 821     }
 822
 823     /// Multiplies `Duration` by `f32`.
 824     ///
 825     /// # Panics
 826     /// This method will panic if result is not finite, negative or overflows `Duration`.
 827     ///
 828     /// # Examples
 829     /// ```
 830     /// use std::time::Duration;
 831     ///
 832     /// let dur = Duration::new(2, 700_000_000);
 833     /// // note that due to rounding errors result is slightly different
 834     /// // from 8.478 and 847800.0
 835     /// assert_eq!(dur.mul_f32(3.14), Duration::new(8, 478_000_640));
 836     /// assert_eq!(dur.mul_f32(3.14e5), Duration::new(847799, 969_120_256));
 837     /// ```
 838     #[stable(feature = "duration_float", since = "1.38.0")]
 839     #[inline]
 840     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 841     pub const fn mul_f32(self, rhs: f32) -> Duration {
 842         Duration::from_secs_f32(rhs * self.as_secs_f32())
 843     }
 844
 845     /// Divide `Duration` by `f64`.
 846     ///
 847     /// # Panics
 848     /// This method will panic if result is not finite, negative or overflows `Duration`.
 849     ///
 850     /// # Examples
 851     /// ```
 852     /// use std::time::Duration;
 853     ///
 854     /// let dur = Duration::new(2, 700_000_000);
 855     /// assert_eq!(dur.div_f64(3.14), Duration::new(0, 859_872_611));
 856     /// // note that truncation is used, not rounding
 857     /// assert_eq!(dur.div_f64(3.14e5), Duration::new(0, 8_598));
 858     /// ```
 859     #[stable(feature = "duration_float", since = "1.38.0")]
 860     #[inline]
 861     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 862     pub const fn div_f64(self, rhs: f64) -> Duration {
 863         Duration::from_secs_f64(self.as_secs_f64() / rhs)
 864     }
 865
 866     /// Divide `Duration` by `f32`.
 867     ///
 868     /// # Panics
 869     /// This method will panic if result is not finite, negative or overflows `Duration`.
 870     ///
 871     /// # Examples
 872     /// ```
 873     /// use std::time::Duration;
 874     ///
 875     /// let dur = Duration::new(2, 700_000_000);
 876     /// // note that due to rounding errors result is slightly
 877     /// // different from 0.859_872_611
 878     /// assert_eq!(dur.div_f32(3.14), Duration::new(0, 859_872_576));
 879     /// // note that truncation is used, not rounding
 880     /// assert_eq!(dur.div_f32(3.14e5), Duration::new(0, 8_598));
 881     /// ```
 882     #[stable(feature = "duration_float", since = "1.38.0")]
 883     #[inline]
 884     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 885     pub const fn div_f32(self, rhs: f32) -> Duration {
 886         Duration::from_secs_f32(self.as_secs_f32() / rhs)
 887     }
 888
 889     /// Divide `Duration` by `Duration` and return `f64`.
 890     ///
 891     /// # Examples
 892     /// ```
 893     /// #![feature(div_duration)]
 894     /// use std::time::Duration;
 895     ///
 896     /// let dur1 = Duration::new(2, 700_000_000);
 897     /// let dur2 = Duration::new(5, 400_000_000);
 898     /// assert_eq!(dur1.div_duration_f64(dur2), 0.5);
 899     /// ```
 900     #[unstable(feature = "div_duration", issue = "63139")]
 901     #[inline]
 902     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 903     pub const fn div_duration_f64(self, rhs: Duration) -> f64 {
 904         self.as_secs_f64() / rhs.as_secs_f64()
 905     }
 906
 907     /// Divide `Duration` by `Duration` and return `f32`.
 908     ///
 909     /// # Examples
 910     /// ```
 911     /// #![feature(div_duration)]
 912     /// use std::time::Duration;
 913     ///
 914     /// let dur1 = Duration::new(2, 700_000_000);
 915     /// let dur2 = Duration::new(5, 400_000_000);
 916     /// assert_eq!(dur1.div_duration_f32(dur2), 0.5);
 917     /// ```
 918     #[unstable(feature = "div_duration", issue = "63139")]
 919     #[inline]
 920     #[rustc_const_unstable(feature = "duration_consts_2", issue = "72440")]
 921     pub const fn div_duration_f32(self, rhs: Duration) -> f32 {
 922         self.as_secs_f32() / rhs.as_secs_f32()
 923     }
 924 }
 925
 926 #[stable(feature = "duration", since = "1.3.0")]
 927 impl Add for Duration {
 928     type Output = Duration;
 929
 930     fn add(self, rhs: Duration) -> Duration {
 931         self.checked_add(rhs).expect("overflow when adding durations")
 932     }
 933 }
 934
 935 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 936 impl AddAssign for Duration {
 937     fn add_assign(&mut self, rhs: Duration) {
 938         *self = *self + rhs;
 939     }
 940 }
 941
 942 #[stable(feature = "duration", since = "1.3.0")]
 943 impl Sub for Duration {
 944     type Output = Duration;
 945
 946     fn sub(self, rhs: Duration) -> Duration {
 947         self.checked_sub(rhs).expect("overflow when subtracting durations")
 948     }
 949 }
 950
 951 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 952 impl SubAssign for Duration {
 953     fn sub_assign(&mut self, rhs: Duration) {
 954         *self = *self - rhs;
 955     }
 956 }
 957
 958 #[stable(feature = "duration", since = "1.3.0")]
 959 impl Mul<u32> for Duration {
 960     type Output = Duration;
 961
 962     fn mul(self, rhs: u32) -> Duration {
 963         self.checked_mul(rhs).expect("overflow when multiplying duration by scalar")
 964     }
 965 }
 966
 967 #[stable(feature = "symmetric_u32_duration_mul", since = "1.31.0")]
 968 impl Mul<Duration> for u32 {
 969     type Output = Duration;
 970
 971     fn mul(self, rhs: Duration) -> Duration {
 972         rhs * self
 973     }
 974 }
 975
 976 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 977 impl MulAssign<u32> for Duration {
 978     fn mul_assign(&mut self, rhs: u32) {
 979         *self = *self * rhs;
 980     }
 981 }
 982
 983 #[stable(feature = "duration", since = "1.3.0")]
 984 impl Div<u32> for Duration {
 985     type Output = Duration;
 986
 987     fn div(self, rhs: u32) -> Duration {
 988         self.checked_div(rhs).expect("divide by zero error when dividing duration by scalar")
 989     }
 990 }
 991
 992 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
 993 impl DivAssign<u32> for Duration {
 994     fn div_assign(&mut self, rhs: u32) {
 995         *self = *self / rhs;
 996     }
 997 }
 998
 999 macro_rules! sum_durations {
1000     ($iter:expr) => {{
1001         let mut total_secs: u64 = 0;
1002         let mut total_nanos: u64 = 0;
1003
1004         for entry in $iter {
1005             total_secs =
1006                 total_secs.checked_add(entry.secs).expect("overflow in iter::sum over durations");
1007             total_nanos = match total_nanos.checked_add(entry.nanos as u64) {
1008                 Some(n) => n,
1009                 None => {
1010                     total_secs = total_secs
1011                         .checked_add(total_nanos / NANOS_PER_SEC as u64)
1012                         .expect("overflow in iter::sum over durations");
1013                     (total_nanos % NANOS_PER_SEC as u64) + entry.nanos as u64
1014                 }
1015             };
1016         }
1017         total_secs = total_secs
1018             .checked_add(total_nanos / NANOS_PER_SEC as u64)
1019             .expect("overflow in iter::sum over durations");
1020         total_nanos = total_nanos % NANOS_PER_SEC as u64;
1021         Duration { secs: total_secs, nanos: total_nanos as u32 }
1022     }};
1023 }
1024
1025 #[stable(feature = "duration_sum", since = "1.16.0")]
1026 impl Sum for Duration {
1027     fn sum<I: Iterator<Item = Duration>>(iter: I) -> Duration {
1028         sum_durations!(iter)
1029     }
1030 }
1031
1032 #[stable(feature = "duration_sum", since = "1.16.0")]
1033 impl<'a> Sum<&'a Duration> for Duration {
1034     fn sum<I: Iterator<Item = &'a Duration>>(iter: I) -> Duration {
1035         sum_durations!(iter)
1036     }
1037 }
1038
1039 #[stable(feature = "duration_debug_impl", since = "1.27.0")]
1040 impl fmt::Debug for Duration {
1041     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1042         /// Formats a floating point number in decimal notation.
1043         ///
1044         /// The number is given as the `integer_part` and a fractional part.
1045         /// The value of the fractional part is `fractional_part / divisor`. So
1046         /// `integer_part` = 3, `fractional_part` = 12 and `divisor` = 100
1047         /// represents the number `3.012`. Trailing zeros are omitted.
1048         ///
1049         /// `divisor` must not be above 100_000_000. It also should be a power
1050         /// of 10, everything else doesn't make sense. `fractional_part` has
1051         /// to be less than `10 * divisor`!
1052         fn fmt_decimal(
1053             f: &mut fmt::Formatter<'_>,
1054             mut integer_part: u64,
1055             mut fractional_part: u32,
1056             mut divisor: u32,
1057         ) -> fmt::Result {
1058             // Encode the fractional part into a temporary buffer. The buffer
1059             // only need to hold 9 elements, because `fractional_part` has to
1060             // be smaller than 10^9. The buffer is prefilled with '0' digits
1061             // to simplify the code below.
1062             let mut buf = [b'0'; 9];
1063
1064             // The next digit is written at this position
1065             let mut pos = 0;
1066
1067             // We keep writing digits into the buffer while there are non-zero
1068             // digits left and we haven't written enough digits yet.
1069             while fractional_part > 0 && pos < f.precision().unwrap_or(9) {
1070                 // Write new digit into the buffer
1071                 buf[pos] = b'0' + (fractional_part / divisor) as u8;
1072
1073                 fractional_part %= divisor;
1074                 divisor /= 10;
1075                 pos += 1;
1076             }
1077
1078             // If a precision < 9 was specified, there may be some non-zero
1079             // digits left that weren't written into the buffer. In that case we
1080             // need to perform rounding to match the semantics of printing
1081             // normal floating point numbers. However, we only need to do work
1082             // when rounding up. This happens if the first digit of the
1083             // remaining ones is >= 5.
1084             if fractional_part > 0 && fractional_part >= divisor * 5 {
1085                 // Round up the number contained in the buffer. We go through
1086                 // the buffer backwards and keep track of the carry.
1087                 let mut rev_pos = pos;
1088                 let mut carry = true;
1089                 while carry && rev_pos > 0 {
1090                     rev_pos -= 1;
1091
1092                     // If the digit in the buffer is not '9', we just need to
1093                     // increment it and can stop then (since we don't have a
1094                     // carry anymore). Otherwise, we set it to '0' (overflow)
1095                     // and continue.
1096                     if buf[rev_pos] < b'9' {
1097                         buf[rev_pos] += 1;
1098                         carry = false;
1099                     } else {
1100                         buf[rev_pos] = b'0';
1101                     }
1102                 }
1103
1104                 // If we still have the carry bit set, that means that we set
1105                 // the whole buffer to '0's and need to increment the integer
1106                 // part.
1107                 if carry {
1108                     integer_part += 1;
1109                 }
1110             }
1111
1112             // Determine the end of the buffer: if precision is set, we just
1113             // use as many digits from the buffer (capped to 9). If it isn't
1114             // set, we only use all digits up to the last non-zero one.
1115             let end = f.precision().map(|p| crate::cmp::min(p, 9)).unwrap_or(pos);
1116
1117             // If we haven't emitted a single fractional digit and the precision
1118             // wasn't set to a non-zero value, we don't print the decimal point.
1119             if end == 0 {
1120                 write!(f, "{}", integer_part)
1121             } else {
1122                 // SAFETY: We are only writing ASCII digits into the buffer and it was
1123                 // initialized with '0's, so it contains valid UTF8.
1124                 let s = unsafe { crate::str::from_utf8_unchecked(&buf[..end]) };
1125
1126                 // If the user request a precision > 9, we pad '0's at the end.
1127                 let w = f.precision().unwrap_or(pos);
1128                 write!(f, "{}.{:0<width$}", integer_part, s, width = w)
1129             }
1130         }
1131
1132         // Print leading '+' sign if requested
1133         if f.sign_plus() {
1134             write!(f, "+")?;
1135         }
1136
1137         if self.secs > 0 {
1138             fmt_decimal(f, self.secs, self.nanos, NANOS_PER_SEC / 10)?;
1139             f.write_str("s")
1140         } else if self.nanos >= NANOS_PER_MILLI {
1141             fmt_decimal(
1142                 f,
1143                 (self.nanos / NANOS_PER_MILLI) as u64,
1144                 self.nanos % NANOS_PER_MILLI,
1145                 NANOS_PER_MILLI / 10,
1146             )?;
1147             f.write_str("ms")
1148         } else if self.nanos >= NANOS_PER_MICRO {
1149             fmt_decimal(
1150                 f,
1151                 (self.nanos / NANOS_PER_MICRO) as u64,
1152                 self.nanos % NANOS_PER_MICRO,
1153                 NANOS_PER_MICRO / 10,
1154             )?;
1155             f.write_str("µs")
1156         } else {
1157             fmt_decimal(f, self.nanos as u64, 0, 1)?;
1158             f.write_str("ns")
1159         }
1160     }
1161 }
1162
1163 /// An error which can be returned when converting a floating-point value of seconds
1164 /// into a [`Duration`].
1165 ///
1166 /// This error is used as the error type for [`Duration::try_from_secs_f32`] and
1167 /// [`Duration::try_from_secs_f64`].
1168 ///
1169 /// # Example
1170 ///
1171 /// ```
1172 /// #![feature(duration_checked_float)]
1173 ///
1174 /// use std::time::Duration;
1175 ///
1176 /// if let Err(e) = Duration::try_from_secs_f32(-1.0) {
1177 ///     println!("Failed conversion to Duration: {}", e);
1178 /// }
1179 /// ```
1180 #[derive(Debug, Clone, PartialEq, Eq)]
1181 #[unstable(feature = "duration_checked_float", issue = "83400")]
1182 pub struct FromSecsError {
1183     kind: FromSecsErrorKind,
1184 }
1185
1186 impl FromSecsError {
1187     const fn description(&self) -> &'static str {
1188         match self.kind {
1189             FromSecsErrorKind::NonFinite => {
1190                 "got non-finite value when converting float to duration"
1191             }
1192             FromSecsErrorKind::Overflow => "overflow when converting float to duration",
1193             FromSecsErrorKind::Underflow => "underflow when converting float to duration",
1194         }
1195     }
1196 }
1197
1198 #[unstable(feature = "duration_checked_float", issue = "83400")]
1199 impl fmt::Display for FromSecsError {
1200     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1201         fmt::Display::fmt(self.description(), f)
1202     }
1203 }
1204
1205 #[derive(Debug, Clone, PartialEq, Eq)]
1206 enum FromSecsErrorKind {
1207     // Value is not a finite value (either infinity or NaN).
1208     NonFinite,
1209     // Value is too large to store in a `Duration`.
1210     Overflow,
1211     // Value is less than `0.0`.
1212     Underflow,
1213 }