core/
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
22use crate::fmt;
23use crate::iter::Sum;
24use crate::num::niche_types::Nanoseconds;
25use crate::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
26
27const NANOS_PER_SEC: u32 = 1_000_000_000;
28const NANOS_PER_MILLI: u32 = 1_000_000;
29const NANOS_PER_MICRO: u32 = 1_000;
30const MILLIS_PER_SEC: u64 = 1_000;
31const MICROS_PER_SEC: u64 = 1_000_000;
32#[unstable(feature = "duration_units", issue = "120301")]
33const SECS_PER_MINUTE: u64 = 60;
34#[unstable(feature = "duration_units", issue = "120301")]
35const MINS_PER_HOUR: u64 = 60;
36#[unstable(feature = "duration_units", issue = "120301")]
37const HOURS_PER_DAY: u64 = 24;
38#[unstable(feature = "duration_units", issue = "120301")]
39const DAYS_PER_WEEK: u64 = 7;
40
41/// A `Duration` type to represent a span of time, typically used for system
42/// timeouts.
43///
44/// Each `Duration` is composed of a whole number of seconds and a fractional part
45/// represented in nanoseconds. If the underlying system does not support
46/// nanosecond-level precision, APIs binding a system timeout will typically round up
47/// the number of nanoseconds.
48///
49/// [`Duration`]s implement many common traits, including [`Add`], [`Sub`], and other
50/// [`ops`] traits. It implements [`Default`] by returning a zero-length `Duration`.
51///
52/// [`ops`]: crate::ops
53///
54/// # Examples
55///
56/// ```
57/// use std::time::Duration;
58///
59/// let five_seconds = Duration::new(5, 0);
60/// let five_seconds_and_five_nanos = five_seconds + Duration::new(0, 5);
61///
62/// assert_eq!(five_seconds_and_five_nanos.as_secs(), 5);
63/// assert_eq!(five_seconds_and_five_nanos.subsec_nanos(), 5);
64///
65/// let ten_millis = Duration::from_millis(10);
66/// ```
67///
68/// # Formatting `Duration` values
69///
70/// `Duration` intentionally does not have a `Display` impl, as there are a
71/// variety of ways to format spans of time for human readability. `Duration`
72/// provides a `Debug` impl that shows the full precision of the value.
73///
74/// The `Debug` output uses the non-ASCII "µs" suffix for microseconds. If your
75/// program output may appear in contexts that cannot rely on full Unicode
76/// compatibility, you may wish to format `Duration` objects yourself or use a
77/// crate to do so.
78#[stable(feature = "duration", since = "1.3.0")]
79#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
80#[cfg_attr(not(test), rustc_diagnostic_item = "Duration")]
81pub struct Duration {
82    secs: u64,
83    nanos: Nanoseconds, // Always 0 <= nanos < NANOS_PER_SEC
84}
85
86impl Duration {
87    /// The duration of one second.
88    ///
89    /// # Examples
90    ///
91    /// ```
92    /// #![feature(duration_constants)]
93    /// use std::time::Duration;
94    ///
95    /// assert_eq!(Duration::SECOND, Duration::from_secs(1));
96    /// ```
97    #[unstable(feature = "duration_constants", issue = "57391")]
98    pub const SECOND: Duration = Duration::from_secs(1);
99
100    /// The duration of one millisecond.
101    ///
102    /// # Examples
103    ///
104    /// ```
105    /// #![feature(duration_constants)]
106    /// use std::time::Duration;
107    ///
108    /// assert_eq!(Duration::MILLISECOND, Duration::from_millis(1));
109    /// ```
110    #[unstable(feature = "duration_constants", issue = "57391")]
111    pub const MILLISECOND: Duration = Duration::from_millis(1);
112
113    /// The duration of one microsecond.
114    ///
115    /// # Examples
116    ///
117    /// ```
118    /// #![feature(duration_constants)]
119    /// use std::time::Duration;
120    ///
121    /// assert_eq!(Duration::MICROSECOND, Duration::from_micros(1));
122    /// ```
123    #[unstable(feature = "duration_constants", issue = "57391")]
124    pub const MICROSECOND: Duration = Duration::from_micros(1);
125
126    /// The duration of one nanosecond.
127    ///
128    /// # Examples
129    ///
130    /// ```
131    /// #![feature(duration_constants)]
132    /// use std::time::Duration;
133    ///
134    /// assert_eq!(Duration::NANOSECOND, Duration::from_nanos(1));
135    /// ```
136    #[unstable(feature = "duration_constants", issue = "57391")]
137    pub const NANOSECOND: Duration = Duration::from_nanos(1);
138
139    /// A duration of zero time.
140    ///
141    /// # Examples
142    ///
143    /// ```
144    /// use std::time::Duration;
145    ///
146    /// let duration = Duration::ZERO;
147    /// assert!(duration.is_zero());
148    /// assert_eq!(duration.as_nanos(), 0);
149    /// ```
150    #[stable(feature = "duration_zero", since = "1.53.0")]
151    pub const ZERO: Duration = Duration::from_nanos(0);
152
153    /// The maximum duration.
154    ///
155    /// May vary by platform as necessary. Must be able to contain the difference between
156    /// two instances of [`Instant`] or two instances of [`SystemTime`].
157    /// This constraint gives it a value of about 584,942,417,355 years in practice,
158    /// which is currently used on all platforms.
159    ///
160    /// # Examples
161    ///
162    /// ```
163    /// use std::time::Duration;
164    ///
165    /// assert_eq!(Duration::MAX, Duration::new(u64::MAX, 1_000_000_000 - 1));
166    /// ```
167    /// [`Instant`]: ../../std/time/struct.Instant.html
168    /// [`SystemTime`]: ../../std/time/struct.SystemTime.html
169    #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
170    pub const MAX: Duration = Duration::new(u64::MAX, NANOS_PER_SEC - 1);
171
172    /// Creates a new `Duration` from the specified number of whole seconds and
173    /// additional nanoseconds.
174    ///
175    /// If the number of nanoseconds is greater than 1 billion (the number of
176    /// nanoseconds in a second), then it will carry over into the seconds provided.
177    ///
178    /// # Panics
179    ///
180    /// This constructor will panic if the carry from the nanoseconds overflows
181    /// the seconds counter.
182    ///
183    /// # Examples
184    ///
185    /// ```
186    /// use std::time::Duration;
187    ///
188    /// let five_seconds = Duration::new(5, 0);
189    /// ```
190    #[stable(feature = "duration", since = "1.3.0")]
191    #[inline]
192    #[must_use]
193    #[rustc_const_stable(feature = "duration_consts_2", since = "1.58.0")]
194    pub const fn new(secs: u64, nanos: u32) -> Duration {
195        if nanos < NANOS_PER_SEC {
196            // SAFETY: nanos < NANOS_PER_SEC, therefore nanos is within the valid range
197            Duration { secs, nanos: unsafe { Nanoseconds::new_unchecked(nanos) } }
198        } else {
199            let secs = secs
200                .checked_add((nanos / NANOS_PER_SEC) as u64)
201                .expect("overflow in Duration::new");
202            let nanos = nanos % NANOS_PER_SEC;
203            // SAFETY: nanos % NANOS_PER_SEC < NANOS_PER_SEC, therefore nanos is within the valid range
204            Duration { secs, nanos: unsafe { Nanoseconds::new_unchecked(nanos) } }
205        }
206    }
207
208    /// Creates a new `Duration` from the specified number of whole seconds.
209    ///
210    /// # Examples
211    ///
212    /// ```
213    /// use std::time::Duration;
214    ///
215    /// let duration = Duration::from_secs(5);
216    ///
217    /// assert_eq!(5, duration.as_secs());
218    /// assert_eq!(0, duration.subsec_nanos());
219    /// ```
220    #[stable(feature = "duration", since = "1.3.0")]
221    #[must_use]
222    #[inline]
223    #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
224    pub const fn from_secs(secs: u64) -> Duration {
225        Duration { secs, nanos: Nanoseconds::ZERO }
226    }
227
228    /// Creates a new `Duration` from the specified number of milliseconds.
229    ///
230    /// # Examples
231    ///
232    /// ```
233    /// use std::time::Duration;
234    ///
235    /// let duration = Duration::from_millis(2_569);
236    ///
237    /// assert_eq!(2, duration.as_secs());
238    /// assert_eq!(569_000_000, duration.subsec_nanos());
239    /// ```
240    #[stable(feature = "duration", since = "1.3.0")]
241    #[must_use]
242    #[inline]
243    #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
244    pub const fn from_millis(millis: u64) -> Duration {
245        let secs = millis / MILLIS_PER_SEC;
246        let subsec_millis = (millis % MILLIS_PER_SEC) as u32;
247        // SAFETY: (x % 1_000) * 1_000_000 < 1_000_000_000
248        //         => x % 1_000 < 1_000
249        let subsec_nanos = unsafe { Nanoseconds::new_unchecked(subsec_millis * NANOS_PER_MILLI) };
250
251        Duration { secs, nanos: subsec_nanos }
252    }
253
254    /// Creates a new `Duration` from the specified number of microseconds.
255    ///
256    /// # Examples
257    ///
258    /// ```
259    /// use std::time::Duration;
260    ///
261    /// let duration = Duration::from_micros(1_000_002);
262    ///
263    /// assert_eq!(1, duration.as_secs());
264    /// assert_eq!(2_000, duration.subsec_nanos());
265    /// ```
266    #[stable(feature = "duration_from_micros", since = "1.27.0")]
267    #[must_use]
268    #[inline]
269    #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
270    pub const fn from_micros(micros: u64) -> Duration {
271        let secs = micros / MICROS_PER_SEC;
272        let subsec_micros = (micros % MICROS_PER_SEC) as u32;
273        // SAFETY: (x % 1_000_000) * 1_000 < 1_000_000_000
274        //         => x % 1_000_000 < 1_000_000
275        let subsec_nanos = unsafe { Nanoseconds::new_unchecked(subsec_micros * NANOS_PER_MICRO) };
276
277        Duration { secs, nanos: subsec_nanos }
278    }
279
280    /// Creates a new `Duration` from the specified number of nanoseconds.
281    ///
282    /// Note: Using this on the return value of `as_nanos()` might cause unexpected behavior:
283    /// `as_nanos()` returns a u128, and can return values that do not fit in u64, e.g. 585 years.
284    /// Instead, consider using the pattern `Duration::new(d.as_secs(), d.subsec_nanos())`
285    /// if you cannot copy/clone the Duration directly.
286    ///
287    /// # Examples
288    ///
289    /// ```
290    /// use std::time::Duration;
291    ///
292    /// let duration = Duration::from_nanos(1_000_000_123);
293    ///
294    /// assert_eq!(1, duration.as_secs());
295    /// assert_eq!(123, duration.subsec_nanos());
296    /// ```
297    #[stable(feature = "duration_extras", since = "1.27.0")]
298    #[must_use]
299    #[inline]
300    #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
301    pub const fn from_nanos(nanos: u64) -> Duration {
302        const NANOS_PER_SEC: u64 = self::NANOS_PER_SEC as u64;
303        let secs = nanos / NANOS_PER_SEC;
304        let subsec_nanos = (nanos % NANOS_PER_SEC) as u32;
305        // SAFETY: x % 1_000_000_000 < 1_000_000_000
306        let subsec_nanos = unsafe { Nanoseconds::new_unchecked(subsec_nanos) };
307
308        Duration { secs, nanos: subsec_nanos }
309    }
310
311    /// Creates a new `Duration` from the specified number of weeks.
312    ///
313    /// # Panics
314    ///
315    /// Panics if the given number of weeks overflows the `Duration` size.
316    ///
317    /// # Examples
318    ///
319    /// ```
320    /// #![feature(duration_constructors)]
321    /// use std::time::Duration;
322    ///
323    /// let duration = Duration::from_weeks(4);
324    ///
325    /// assert_eq!(4 * 7 * 24 * 60 * 60, duration.as_secs());
326    /// assert_eq!(0, duration.subsec_nanos());
327    /// ```
328    #[unstable(feature = "duration_constructors", issue = "120301")]
329    #[must_use]
330    #[inline]
331    pub const fn from_weeks(weeks: u64) -> Duration {
332        if weeks > u64::MAX / (SECS_PER_MINUTE * MINS_PER_HOUR * HOURS_PER_DAY * DAYS_PER_WEEK) {
333            panic!("overflow in Duration::from_weeks");
334        }
335
336        Duration::from_secs(weeks * MINS_PER_HOUR * SECS_PER_MINUTE * HOURS_PER_DAY * DAYS_PER_WEEK)
337    }
338
339    /// Creates a new `Duration` from the specified number of days.
340    ///
341    /// # Panics
342    ///
343    /// Panics if the given number of days overflows the `Duration` size.
344    ///
345    /// # Examples
346    ///
347    /// ```
348    /// #![feature(duration_constructors)]
349    /// use std::time::Duration;
350    ///
351    /// let duration = Duration::from_days(7);
352    ///
353    /// assert_eq!(7 * 24 * 60 * 60, duration.as_secs());
354    /// assert_eq!(0, duration.subsec_nanos());
355    /// ```
356    #[unstable(feature = "duration_constructors", issue = "120301")]
357    #[must_use]
358    #[inline]
359    pub const fn from_days(days: u64) -> Duration {
360        if days > u64::MAX / (SECS_PER_MINUTE * MINS_PER_HOUR * HOURS_PER_DAY) {
361            panic!("overflow in Duration::from_days");
362        }
363
364        Duration::from_secs(days * MINS_PER_HOUR * SECS_PER_MINUTE * HOURS_PER_DAY)
365    }
366
367    /// Creates a new `Duration` from the specified number of hours.
368    ///
369    /// # Panics
370    ///
371    /// Panics if the given number of hours overflows the `Duration` size.
372    ///
373    /// # Examples
374    ///
375    /// ```
376    /// #![feature(duration_constructors)]
377    /// use std::time::Duration;
378    ///
379    /// let duration = Duration::from_hours(6);
380    ///
381    /// assert_eq!(6 * 60 * 60, duration.as_secs());
382    /// assert_eq!(0, duration.subsec_nanos());
383    /// ```
384    #[unstable(feature = "duration_constructors", issue = "120301")]
385    #[must_use]
386    #[inline]
387    pub const fn from_hours(hours: u64) -> Duration {
388        if hours > u64::MAX / (SECS_PER_MINUTE * MINS_PER_HOUR) {
389            panic!("overflow in Duration::from_hours");
390        }
391
392        Duration::from_secs(hours * MINS_PER_HOUR * SECS_PER_MINUTE)
393    }
394
395    /// Creates a new `Duration` from the specified number of minutes.
396    ///
397    /// # Panics
398    ///
399    /// Panics if the given number of minutes overflows the `Duration` size.
400    ///
401    /// # Examples
402    ///
403    /// ```
404    /// #![feature(duration_constructors)]
405    /// use std::time::Duration;
406    ///
407    /// let duration = Duration::from_mins(10);
408    ///
409    /// assert_eq!(10 * 60, duration.as_secs());
410    /// assert_eq!(0, duration.subsec_nanos());
411    /// ```
412    #[unstable(feature = "duration_constructors", issue = "120301")]
413    #[must_use]
414    #[inline]
415    pub const fn from_mins(mins: u64) -> Duration {
416        if mins > u64::MAX / SECS_PER_MINUTE {
417            panic!("overflow in Duration::from_mins");
418        }
419
420        Duration::from_secs(mins * SECS_PER_MINUTE)
421    }
422
423    /// Returns true if this `Duration` spans no time.
424    ///
425    /// # Examples
426    ///
427    /// ```
428    /// use std::time::Duration;
429    ///
430    /// assert!(Duration::ZERO.is_zero());
431    /// assert!(Duration::new(0, 0).is_zero());
432    /// assert!(Duration::from_nanos(0).is_zero());
433    /// assert!(Duration::from_secs(0).is_zero());
434    ///
435    /// assert!(!Duration::new(1, 1).is_zero());
436    /// assert!(!Duration::from_nanos(1).is_zero());
437    /// assert!(!Duration::from_secs(1).is_zero());
438    /// ```
439    #[must_use]
440    #[stable(feature = "duration_zero", since = "1.53.0")]
441    #[rustc_const_stable(feature = "duration_zero", since = "1.53.0")]
442    #[inline]
443    pub const fn is_zero(&self) -> bool {
444        self.secs == 0 && self.nanos.as_inner() == 0
445    }
446
447    /// Returns the number of _whole_ seconds contained by this `Duration`.
448    ///
449    /// The returned value does not include the fractional (nanosecond) part of the
450    /// duration, which can be obtained using [`subsec_nanos`].
451    ///
452    /// # Examples
453    ///
454    /// ```
455    /// use std::time::Duration;
456    ///
457    /// let duration = Duration::new(5, 730_023_852);
458    /// assert_eq!(duration.as_secs(), 5);
459    /// ```
460    ///
461    /// To determine the total number of seconds represented by the `Duration`
462    /// including the fractional part, use [`as_secs_f64`] or [`as_secs_f32`]
463    ///
464    /// [`as_secs_f64`]: Duration::as_secs_f64
465    /// [`as_secs_f32`]: Duration::as_secs_f32
466    /// [`subsec_nanos`]: Duration::subsec_nanos
467    #[stable(feature = "duration", since = "1.3.0")]
468    #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
469    #[must_use]
470    #[inline]
471    pub const fn as_secs(&self) -> u64 {
472        self.secs
473    }
474
475    /// Returns the fractional part of this `Duration`, in whole milliseconds.
476    ///
477    /// This method does **not** return the length of the duration when
478    /// represented by milliseconds. The returned number always represents a
479    /// fractional portion of a second (i.e., it is less than one thousand).
480    ///
481    /// # Examples
482    ///
483    /// ```
484    /// use std::time::Duration;
485    ///
486    /// let duration = Duration::from_millis(5_432);
487    /// assert_eq!(duration.as_secs(), 5);
488    /// assert_eq!(duration.subsec_millis(), 432);
489    /// ```
490    #[stable(feature = "duration_extras", since = "1.27.0")]
491    #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
492    #[must_use]
493    #[inline]
494    pub const fn subsec_millis(&self) -> u32 {
495        self.nanos.as_inner() / NANOS_PER_MILLI
496    }
497
498    /// Returns the fractional part of this `Duration`, in whole microseconds.
499    ///
500    /// This method does **not** return the length of the duration when
501    /// represented by microseconds. The returned number always represents a
502    /// fractional portion of a second (i.e., it is less than one million).
503    ///
504    /// # Examples
505    ///
506    /// ```
507    /// use std::time::Duration;
508    ///
509    /// let duration = Duration::from_micros(1_234_567);
510    /// assert_eq!(duration.as_secs(), 1);
511    /// assert_eq!(duration.subsec_micros(), 234_567);
512    /// ```
513    #[stable(feature = "duration_extras", since = "1.27.0")]
514    #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
515    #[must_use]
516    #[inline]
517    pub const fn subsec_micros(&self) -> u32 {
518        self.nanos.as_inner() / NANOS_PER_MICRO
519    }
520
521    /// Returns the fractional part of this `Duration`, in nanoseconds.
522    ///
523    /// This method does **not** return the length of the duration when
524    /// represented by nanoseconds. The returned number always represents a
525    /// fractional portion of a second (i.e., it is less than one billion).
526    ///
527    /// # Examples
528    ///
529    /// ```
530    /// use std::time::Duration;
531    ///
532    /// let duration = Duration::from_millis(5_010);
533    /// assert_eq!(duration.as_secs(), 5);
534    /// assert_eq!(duration.subsec_nanos(), 10_000_000);
535    /// ```
536    #[stable(feature = "duration", since = "1.3.0")]
537    #[rustc_const_stable(feature = "duration_consts", since = "1.32.0")]
538    #[must_use]
539    #[inline]
540    pub const fn subsec_nanos(&self) -> u32 {
541        self.nanos.as_inner()
542    }
543
544    /// Returns the total number of whole milliseconds contained by this `Duration`.
545    ///
546    /// # Examples
547    ///
548    /// ```
549    /// use std::time::Duration;
550    ///
551    /// let duration = Duration::new(5, 730_023_852);
552    /// assert_eq!(duration.as_millis(), 5_730);
553    /// ```
554    #[stable(feature = "duration_as_u128", since = "1.33.0")]
555    #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
556    #[must_use]
557    #[inline]
558    pub const fn as_millis(&self) -> u128 {
559        self.secs as u128 * MILLIS_PER_SEC as u128
560            + (self.nanos.as_inner() / NANOS_PER_MILLI) as u128
561    }
562
563    /// Returns the total number of whole microseconds contained by this `Duration`.
564    ///
565    /// # Examples
566    ///
567    /// ```
568    /// use std::time::Duration;
569    ///
570    /// let duration = Duration::new(5, 730_023_852);
571    /// assert_eq!(duration.as_micros(), 5_730_023);
572    /// ```
573    #[stable(feature = "duration_as_u128", since = "1.33.0")]
574    #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
575    #[must_use]
576    #[inline]
577    pub const fn as_micros(&self) -> u128 {
578        self.secs as u128 * MICROS_PER_SEC as u128
579            + (self.nanos.as_inner() / NANOS_PER_MICRO) as u128
580    }
581
582    /// Returns the total number of nanoseconds contained by this `Duration`.
583    ///
584    /// # Examples
585    ///
586    /// ```
587    /// use std::time::Duration;
588    ///
589    /// let duration = Duration::new(5, 730_023_852);
590    /// assert_eq!(duration.as_nanos(), 5_730_023_852);
591    /// ```
592    #[stable(feature = "duration_as_u128", since = "1.33.0")]
593    #[rustc_const_stable(feature = "duration_as_u128", since = "1.33.0")]
594    #[must_use]
595    #[inline]
596    pub const fn as_nanos(&self) -> u128 {
597        self.secs as u128 * NANOS_PER_SEC as u128 + self.nanos.as_inner() as u128
598    }
599
600    /// Computes the absolute difference between `self` and `other`.
601    ///
602    /// # Examples
603    ///
604    /// ```
605    /// use std::time::Duration;
606    ///
607    /// assert_eq!(Duration::new(100, 0).abs_diff(Duration::new(80, 0)), Duration::new(20, 0));
608    /// assert_eq!(Duration::new(100, 400_000_000).abs_diff(Duration::new(110, 0)), Duration::new(9, 600_000_000));
609    /// ```
610    #[stable(feature = "duration_abs_diff", since = "1.81.0")]
611    #[rustc_const_stable(feature = "duration_abs_diff", since = "1.81.0")]
612    #[must_use = "this returns the result of the operation, \
613                  without modifying the original"]
614    #[inline]
615    pub const fn abs_diff(self, other: Duration) -> Duration {
616        if let Some(res) = self.checked_sub(other) { res } else { other.checked_sub(self).unwrap() }
617    }
618
619    /// Checked `Duration` addition. Computes `self + other`, returning [`None`]
620    /// if overflow occurred.
621    ///
622    /// # Examples
623    ///
624    /// ```
625    /// use std::time::Duration;
626    ///
627    /// assert_eq!(Duration::new(0, 0).checked_add(Duration::new(0, 1)), Some(Duration::new(0, 1)));
628    /// assert_eq!(Duration::new(1, 0).checked_add(Duration::new(u64::MAX, 0)), None);
629    /// ```
630    #[stable(feature = "duration_checked_ops", since = "1.16.0")]
631    #[must_use = "this returns the result of the operation, \
632                  without modifying the original"]
633    #[inline]
634    #[rustc_const_stable(feature = "duration_consts_2", since = "1.58.0")]
635    pub const fn checked_add(self, rhs: Duration) -> Option<Duration> {
636        if let Some(mut secs) = self.secs.checked_add(rhs.secs) {
637            let mut nanos = self.nanos.as_inner() + rhs.nanos.as_inner();
638            if nanos >= NANOS_PER_SEC {
639                nanos -= NANOS_PER_SEC;
640                if let Some(new_secs) = secs.checked_add(1) {
641                    secs = new_secs;
642                } else {
643                    return None;
644                }
645            }
646            debug_assert!(nanos < NANOS_PER_SEC);
647            Some(Duration::new(secs, nanos))
648        } else {
649            None
650        }
651    }
652
653    /// Saturating `Duration` addition. Computes `self + other`, returning [`Duration::MAX`]
654    /// if overflow occurred.
655    ///
656    /// # Examples
657    ///
658    /// ```
659    /// #![feature(duration_constants)]
660    /// use std::time::Duration;
661    ///
662    /// assert_eq!(Duration::new(0, 0).saturating_add(Duration::new(0, 1)), Duration::new(0, 1));
663    /// assert_eq!(Duration::new(1, 0).saturating_add(Duration::new(u64::MAX, 0)), Duration::MAX);
664    /// ```
665    #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
666    #[must_use = "this returns the result of the operation, \
667                  without modifying the original"]
668    #[inline]
669    #[rustc_const_stable(feature = "duration_consts_2", since = "1.58.0")]
670    pub const fn saturating_add(self, rhs: Duration) -> Duration {
671        match self.checked_add(rhs) {
672            Some(res) => res,
673            None => Duration::MAX,
674        }
675    }
676
677    /// Checked `Duration` subtraction. Computes `self - other`, returning [`None`]
678    /// if the result would be negative or if overflow occurred.
679    ///
680    /// # Examples
681    ///
682    /// ```
683    /// use std::time::Duration;
684    ///
685    /// assert_eq!(Duration::new(0, 1).checked_sub(Duration::new(0, 0)), Some(Duration::new(0, 1)));
686    /// assert_eq!(Duration::new(0, 0).checked_sub(Duration::new(0, 1)), None);
687    /// ```
688    #[stable(feature = "duration_checked_ops", since = "1.16.0")]
689    #[must_use = "this returns the result of the operation, \
690                  without modifying the original"]
691    #[inline]
692    #[rustc_const_stable(feature = "duration_consts_2", since = "1.58.0")]
693    pub const fn checked_sub(self, rhs: Duration) -> Option<Duration> {
694        if let Some(mut secs) = self.secs.checked_sub(rhs.secs) {
695            let nanos = if self.nanos.as_inner() >= rhs.nanos.as_inner() {
696                self.nanos.as_inner() - rhs.nanos.as_inner()
697            } else if let Some(sub_secs) = secs.checked_sub(1) {
698                secs = sub_secs;
699                self.nanos.as_inner() + NANOS_PER_SEC - rhs.nanos.as_inner()
700            } else {
701                return None;
702            };
703            debug_assert!(nanos < NANOS_PER_SEC);
704            Some(Duration::new(secs, nanos))
705        } else {
706            None
707        }
708    }
709
710    /// Saturating `Duration` subtraction. Computes `self - other`, returning [`Duration::ZERO`]
711    /// if the result would be negative or if overflow occurred.
712    ///
713    /// # Examples
714    ///
715    /// ```
716    /// use std::time::Duration;
717    ///
718    /// assert_eq!(Duration::new(0, 1).saturating_sub(Duration::new(0, 0)), Duration::new(0, 1));
719    /// assert_eq!(Duration::new(0, 0).saturating_sub(Duration::new(0, 1)), Duration::ZERO);
720    /// ```
721    #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
722    #[must_use = "this returns the result of the operation, \
723                  without modifying the original"]
724    #[inline]
725    #[rustc_const_stable(feature = "duration_consts_2", since = "1.58.0")]
726    pub const fn saturating_sub(self, rhs: Duration) -> Duration {
727        match self.checked_sub(rhs) {
728            Some(res) => res,
729            None => Duration::ZERO,
730        }
731    }
732
733    /// Checked `Duration` multiplication. Computes `self * other`, returning
734    /// [`None`] if overflow occurred.
735    ///
736    /// # Examples
737    ///
738    /// ```
739    /// use std::time::Duration;
740    ///
741    /// assert_eq!(Duration::new(0, 500_000_001).checked_mul(2), Some(Duration::new(1, 2)));
742    /// assert_eq!(Duration::new(u64::MAX - 1, 0).checked_mul(2), None);
743    /// ```
744    #[stable(feature = "duration_checked_ops", since = "1.16.0")]
745    #[must_use = "this returns the result of the operation, \
746                  without modifying the original"]
747    #[inline]
748    #[rustc_const_stable(feature = "duration_consts_2", since = "1.58.0")]
749    pub const fn checked_mul(self, rhs: u32) -> Option<Duration> {
750        // Multiply nanoseconds as u64, because it cannot overflow that way.
751        let total_nanos = self.nanos.as_inner() as u64 * rhs as u64;
752        let extra_secs = total_nanos / (NANOS_PER_SEC as u64);
753        let nanos = (total_nanos % (NANOS_PER_SEC as u64)) as u32;
754        // FIXME(const-hack): use `and_then` once that is possible.
755        if let Some(s) = self.secs.checked_mul(rhs as u64) {
756            if let Some(secs) = s.checked_add(extra_secs) {
757                debug_assert!(nanos < NANOS_PER_SEC);
758                return Some(Duration::new(secs, nanos));
759            }
760        }
761        None
762    }
763
764    /// Saturating `Duration` multiplication. Computes `self * other`, returning
765    /// [`Duration::MAX`] if overflow occurred.
766    ///
767    /// # Examples
768    ///
769    /// ```
770    /// #![feature(duration_constants)]
771    /// use std::time::Duration;
772    ///
773    /// assert_eq!(Duration::new(0, 500_000_001).saturating_mul(2), Duration::new(1, 2));
774    /// assert_eq!(Duration::new(u64::MAX - 1, 0).saturating_mul(2), Duration::MAX);
775    /// ```
776    #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
777    #[must_use = "this returns the result of the operation, \
778                  without modifying the original"]
779    #[inline]
780    #[rustc_const_stable(feature = "duration_consts_2", since = "1.58.0")]
781    pub const fn saturating_mul(self, rhs: u32) -> Duration {
782        match self.checked_mul(rhs) {
783            Some(res) => res,
784            None => Duration::MAX,
785        }
786    }
787
788    /// Checked `Duration` division. Computes `self / other`, returning [`None`]
789    /// if `other == 0`.
790    ///
791    /// # Examples
792    ///
793    /// ```
794    /// use std::time::Duration;
795    ///
796    /// assert_eq!(Duration::new(2, 0).checked_div(2), Some(Duration::new(1, 0)));
797    /// assert_eq!(Duration::new(1, 0).checked_div(2), Some(Duration::new(0, 500_000_000)));
798    /// assert_eq!(Duration::new(2, 0).checked_div(0), None);
799    /// ```
800    #[stable(feature = "duration_checked_ops", since = "1.16.0")]
801    #[must_use = "this returns the result of the operation, \
802                  without modifying the original"]
803    #[inline]
804    #[rustc_const_stable(feature = "duration_consts_2", since = "1.58.0")]
805    pub const fn checked_div(self, rhs: u32) -> Option<Duration> {
806        if rhs != 0 {
807            let (secs, extra_secs) = (self.secs / (rhs as u64), self.secs % (rhs as u64));
808            let (mut nanos, extra_nanos) =
809                (self.nanos.as_inner() / rhs, self.nanos.as_inner() % rhs);
810            nanos +=
811                ((extra_secs * (NANOS_PER_SEC as u64) + extra_nanos as u64) / (rhs as u64)) as u32;
812            debug_assert!(nanos < NANOS_PER_SEC);
813            Some(Duration::new(secs, nanos))
814        } else {
815            None
816        }
817    }
818
819    /// Returns the number of seconds contained by this `Duration` as `f64`.
820    ///
821    /// The returned value includes the fractional (nanosecond) part of the duration.
822    ///
823    /// # Examples
824    /// ```
825    /// use std::time::Duration;
826    ///
827    /// let dur = Duration::new(2, 700_000_000);
828    /// assert_eq!(dur.as_secs_f64(), 2.7);
829    /// ```
830    #[stable(feature = "duration_float", since = "1.38.0")]
831    #[must_use]
832    #[inline]
833    #[rustc_const_stable(feature = "duration_consts_float", since = "1.83.0")]
834    pub const fn as_secs_f64(&self) -> f64 {
835        (self.secs as f64) + (self.nanos.as_inner() as f64) / (NANOS_PER_SEC as f64)
836    }
837
838    /// Returns the number of seconds contained by this `Duration` as `f32`.
839    ///
840    /// The returned value includes the fractional (nanosecond) part of the duration.
841    ///
842    /// # Examples
843    /// ```
844    /// use std::time::Duration;
845    ///
846    /// let dur = Duration::new(2, 700_000_000);
847    /// assert_eq!(dur.as_secs_f32(), 2.7);
848    /// ```
849    #[stable(feature = "duration_float", since = "1.38.0")]
850    #[must_use]
851    #[inline]
852    #[rustc_const_stable(feature = "duration_consts_float", since = "1.83.0")]
853    pub const fn as_secs_f32(&self) -> f32 {
854        (self.secs as f32) + (self.nanos.as_inner() as f32) / (NANOS_PER_SEC as f32)
855    }
856
857    /// Returns the number of milliseconds contained by this `Duration` as `f64`.
858    ///
859    /// The returned value includes the fractional (nanosecond) part of the duration.
860    ///
861    /// # Examples
862    /// ```
863    /// #![feature(duration_millis_float)]
864    /// use std::time::Duration;
865    ///
866    /// let dur = Duration::new(2, 345_678_000);
867    /// assert_eq!(dur.as_millis_f64(), 2_345.678);
868    /// ```
869    #[unstable(feature = "duration_millis_float", issue = "122451")]
870    #[must_use]
871    #[inline]
872    pub const fn as_millis_f64(&self) -> f64 {
873        (self.secs as f64) * (MILLIS_PER_SEC as f64)
874            + (self.nanos.as_inner() as f64) / (NANOS_PER_MILLI as f64)
875    }
876
877    /// Returns the number of milliseconds contained by this `Duration` as `f32`.
878    ///
879    /// The returned value includes the fractional (nanosecond) part of the duration.
880    ///
881    /// # Examples
882    /// ```
883    /// #![feature(duration_millis_float)]
884    /// use std::time::Duration;
885    ///
886    /// let dur = Duration::new(2, 345_678_000);
887    /// assert_eq!(dur.as_millis_f32(), 2_345.678);
888    /// ```
889    #[unstable(feature = "duration_millis_float", issue = "122451")]
890    #[must_use]
891    #[inline]
892    pub const fn as_millis_f32(&self) -> f32 {
893        (self.secs as f32) * (MILLIS_PER_SEC as f32)
894            + (self.nanos.as_inner() as f32) / (NANOS_PER_MILLI as f32)
895    }
896
897    /// Creates a new `Duration` from the specified number of seconds represented
898    /// as `f64`.
899    ///
900    /// # Panics
901    /// This constructor will panic if `secs` is negative, overflows `Duration` or not finite.
902    ///
903    /// # Examples
904    /// ```
905    /// use std::time::Duration;
906    ///
907    /// let res = Duration::from_secs_f64(0.0);
908    /// assert_eq!(res, Duration::new(0, 0));
909    /// let res = Duration::from_secs_f64(1e-20);
910    /// assert_eq!(res, Duration::new(0, 0));
911    /// let res = Duration::from_secs_f64(4.2e-7);
912    /// assert_eq!(res, Duration::new(0, 420));
913    /// let res = Duration::from_secs_f64(2.7);
914    /// assert_eq!(res, Duration::new(2, 700_000_000));
915    /// let res = Duration::from_secs_f64(3e10);
916    /// assert_eq!(res, Duration::new(30_000_000_000, 0));
917    /// // subnormal float
918    /// let res = Duration::from_secs_f64(f64::from_bits(1));
919    /// assert_eq!(res, Duration::new(0, 0));
920    /// // conversion uses rounding
921    /// let res = Duration::from_secs_f64(0.999e-9);
922    /// assert_eq!(res, Duration::new(0, 1));
923    /// ```
924    #[stable(feature = "duration_float", since = "1.38.0")]
925    #[must_use]
926    #[inline]
927    pub fn from_secs_f64(secs: f64) -> Duration {
928        match Duration::try_from_secs_f64(secs) {
929            Ok(v) => v,
930            Err(e) => panic!("{}", e.description()),
931        }
932    }
933
934    /// Creates a new `Duration` from the specified number of seconds represented
935    /// as `f32`.
936    ///
937    /// # Panics
938    /// This constructor will panic if `secs` is negative, overflows `Duration` or not finite.
939    ///
940    /// # Examples
941    /// ```
942    /// use std::time::Duration;
943    ///
944    /// let res = Duration::from_secs_f32(0.0);
945    /// assert_eq!(res, Duration::new(0, 0));
946    /// let res = Duration::from_secs_f32(1e-20);
947    /// assert_eq!(res, Duration::new(0, 0));
948    /// let res = Duration::from_secs_f32(4.2e-7);
949    /// assert_eq!(res, Duration::new(0, 420));
950    /// let res = Duration::from_secs_f32(2.7);
951    /// assert_eq!(res, Duration::new(2, 700_000_048));
952    /// let res = Duration::from_secs_f32(3e10);
953    /// assert_eq!(res, Duration::new(30_000_001_024, 0));
954    /// // subnormal float
955    /// let res = Duration::from_secs_f32(f32::from_bits(1));
956    /// assert_eq!(res, Duration::new(0, 0));
957    /// // conversion uses rounding
958    /// let res = Duration::from_secs_f32(0.999e-9);
959    /// assert_eq!(res, Duration::new(0, 1));
960    /// ```
961    #[stable(feature = "duration_float", since = "1.38.0")]
962    #[must_use]
963    #[inline]
964    pub fn from_secs_f32(secs: f32) -> Duration {
965        match Duration::try_from_secs_f32(secs) {
966            Ok(v) => v,
967            Err(e) => panic!("{}", e.description()),
968        }
969    }
970
971    /// Multiplies `Duration` by `f64`.
972    ///
973    /// # Panics
974    /// This method will panic if result is negative, overflows `Duration` or not finite.
975    ///
976    /// # Examples
977    /// ```
978    /// use std::time::Duration;
979    ///
980    /// let dur = Duration::new(2, 700_000_000);
981    /// assert_eq!(dur.mul_f64(3.14), Duration::new(8, 478_000_000));
982    /// assert_eq!(dur.mul_f64(3.14e5), Duration::new(847_800, 0));
983    /// ```
984    #[stable(feature = "duration_float", since = "1.38.0")]
985    #[must_use = "this returns the result of the operation, \
986                  without modifying the original"]
987    #[inline]
988    pub fn mul_f64(self, rhs: f64) -> Duration {
989        Duration::from_secs_f64(rhs * self.as_secs_f64())
990    }
991
992    /// Multiplies `Duration` by `f32`.
993    ///
994    /// # Panics
995    /// This method will panic if result is negative, overflows `Duration` or not finite.
996    ///
997    /// # Examples
998    /// ```
999    /// use std::time::Duration;
1000    ///
1001    /// let dur = Duration::new(2, 700_000_000);
1002    /// assert_eq!(dur.mul_f32(3.14), Duration::new(8, 478_000_641));
1003    /// assert_eq!(dur.mul_f32(3.14e5), Duration::new(847_800, 0));
1004    /// ```
1005    #[stable(feature = "duration_float", since = "1.38.0")]
1006    #[must_use = "this returns the result of the operation, \
1007                  without modifying the original"]
1008    #[inline]
1009    pub fn mul_f32(self, rhs: f32) -> Duration {
1010        Duration::from_secs_f32(rhs * self.as_secs_f32())
1011    }
1012
1013    /// Divides `Duration` by `f64`.
1014    ///
1015    /// # Panics
1016    /// This method will panic if result is negative, overflows `Duration` or not finite.
1017    ///
1018    /// # Examples
1019    /// ```
1020    /// use std::time::Duration;
1021    ///
1022    /// let dur = Duration::new(2, 700_000_000);
1023    /// assert_eq!(dur.div_f64(3.14), Duration::new(0, 859_872_611));
1024    /// assert_eq!(dur.div_f64(3.14e5), Duration::new(0, 8_599));
1025    /// ```
1026    #[stable(feature = "duration_float", since = "1.38.0")]
1027    #[must_use = "this returns the result of the operation, \
1028                  without modifying the original"]
1029    #[inline]
1030    pub fn div_f64(self, rhs: f64) -> Duration {
1031        Duration::from_secs_f64(self.as_secs_f64() / rhs)
1032    }
1033
1034    /// Divides `Duration` by `f32`.
1035    ///
1036    /// # Panics
1037    /// This method will panic if result is negative, overflows `Duration` or not finite.
1038    ///
1039    /// # Examples
1040    /// ```
1041    /// use std::time::Duration;
1042    ///
1043    /// let dur = Duration::new(2, 700_000_000);
1044    /// // note that due to rounding errors result is slightly
1045    /// // different from 0.859_872_611
1046    /// assert_eq!(dur.div_f32(3.14), Duration::new(0, 859_872_580));
1047    /// assert_eq!(dur.div_f32(3.14e5), Duration::new(0, 8_599));
1048    /// ```
1049    #[stable(feature = "duration_float", since = "1.38.0")]
1050    #[must_use = "this returns the result of the operation, \
1051                  without modifying the original"]
1052    #[inline]
1053    pub fn div_f32(self, rhs: f32) -> Duration {
1054        Duration::from_secs_f32(self.as_secs_f32() / rhs)
1055    }
1056
1057    /// Divides `Duration` by `Duration` and returns `f64`.
1058    ///
1059    /// # Examples
1060    /// ```
1061    /// use std::time::Duration;
1062    ///
1063    /// let dur1 = Duration::new(2, 700_000_000);
1064    /// let dur2 = Duration::new(5, 400_000_000);
1065    /// assert_eq!(dur1.div_duration_f64(dur2), 0.5);
1066    /// ```
1067    #[stable(feature = "div_duration", since = "1.80.0")]
1068    #[must_use = "this returns the result of the operation, \
1069                  without modifying the original"]
1070    #[inline]
1071    #[rustc_const_stable(feature = "duration_consts_float", since = "1.83.0")]
1072    pub const fn div_duration_f64(self, rhs: Duration) -> f64 {
1073        let self_nanos =
1074            (self.secs as f64) * (NANOS_PER_SEC as f64) + (self.nanos.as_inner() as f64);
1075        let rhs_nanos = (rhs.secs as f64) * (NANOS_PER_SEC as f64) + (rhs.nanos.as_inner() as f64);
1076        self_nanos / rhs_nanos
1077    }
1078
1079    /// Divides `Duration` by `Duration` and returns `f32`.
1080    ///
1081    /// # Examples
1082    /// ```
1083    /// use std::time::Duration;
1084    ///
1085    /// let dur1 = Duration::new(2, 700_000_000);
1086    /// let dur2 = Duration::new(5, 400_000_000);
1087    /// assert_eq!(dur1.div_duration_f32(dur2), 0.5);
1088    /// ```
1089    #[stable(feature = "div_duration", since = "1.80.0")]
1090    #[must_use = "this returns the result of the operation, \
1091                  without modifying the original"]
1092    #[inline]
1093    #[rustc_const_stable(feature = "duration_consts_float", since = "1.83.0")]
1094    pub const fn div_duration_f32(self, rhs: Duration) -> f32 {
1095        let self_nanos =
1096            (self.secs as f32) * (NANOS_PER_SEC as f32) + (self.nanos.as_inner() as f32);
1097        let rhs_nanos = (rhs.secs as f32) * (NANOS_PER_SEC as f32) + (rhs.nanos.as_inner() as f32);
1098        self_nanos / rhs_nanos
1099    }
1100}
1101
1102#[stable(feature = "duration", since = "1.3.0")]
1103impl Add for Duration {
1104    type Output = Duration;
1105
1106    #[inline]
1107    fn add(self, rhs: Duration) -> Duration {
1108        self.checked_add(rhs).expect("overflow when adding durations")
1109    }
1110}
1111
1112#[stable(feature = "time_augmented_assignment", since = "1.9.0")]
1113impl AddAssign for Duration {
1114    #[inline]
1115    fn add_assign(&mut self, rhs: Duration) {
1116        *self = *self + rhs;
1117    }
1118}
1119
1120#[stable(feature = "duration", since = "1.3.0")]
1121impl Sub for Duration {
1122    type Output = Duration;
1123
1124    #[inline]
1125    fn sub(self, rhs: Duration) -> Duration {
1126        self.checked_sub(rhs).expect("overflow when subtracting durations")
1127    }
1128}
1129
1130#[stable(feature = "time_augmented_assignment", since = "1.9.0")]
1131impl SubAssign for Duration {
1132    #[inline]
1133    fn sub_assign(&mut self, rhs: Duration) {
1134        *self = *self - rhs;
1135    }
1136}
1137
1138#[stable(feature = "duration", since = "1.3.0")]
1139impl Mul<u32> for Duration {
1140    type Output = Duration;
1141
1142    #[inline]
1143    fn mul(self, rhs: u32) -> Duration {
1144        self.checked_mul(rhs).expect("overflow when multiplying duration by scalar")
1145    }
1146}
1147
1148#[stable(feature = "symmetric_u32_duration_mul", since = "1.31.0")]
1149impl Mul<Duration> for u32 {
1150    type Output = Duration;
1151
1152    #[inline]
1153    fn mul(self, rhs: Duration) -> Duration {
1154        rhs * self
1155    }
1156}
1157
1158#[stable(feature = "time_augmented_assignment", since = "1.9.0")]
1159impl MulAssign<u32> for Duration {
1160    #[inline]
1161    fn mul_assign(&mut self, rhs: u32) {
1162        *self = *self * rhs;
1163    }
1164}
1165
1166#[stable(feature = "duration", since = "1.3.0")]
1167impl Div<u32> for Duration {
1168    type Output = Duration;
1169
1170    #[inline]
1171    fn div(self, rhs: u32) -> Duration {
1172        self.checked_div(rhs).expect("divide by zero error when dividing duration by scalar")
1173    }
1174}
1175
1176#[stable(feature = "time_augmented_assignment", since = "1.9.0")]
1177impl DivAssign<u32> for Duration {
1178    #[inline]
1179    fn div_assign(&mut self, rhs: u32) {
1180        *self = *self / rhs;
1181    }
1182}
1183
1184macro_rules! sum_durations {
1185    ($iter:expr) => {{
1186        let mut total_secs: u64 = 0;
1187        let mut total_nanos: u64 = 0;
1188
1189        for entry in $iter {
1190            total_secs =
1191                total_secs.checked_add(entry.secs).expect("overflow in iter::sum over durations");
1192            total_nanos = match total_nanos.checked_add(entry.nanos.as_inner() as u64) {
1193                Some(n) => n,
1194                None => {
1195                    total_secs = total_secs
1196                        .checked_add(total_nanos / NANOS_PER_SEC as u64)
1197                        .expect("overflow in iter::sum over durations");
1198                    (total_nanos % NANOS_PER_SEC as u64) + entry.nanos.as_inner() as u64
1199                }
1200            };
1201        }
1202        total_secs = total_secs
1203            .checked_add(total_nanos / NANOS_PER_SEC as u64)
1204            .expect("overflow in iter::sum over durations");
1205        total_nanos = total_nanos % NANOS_PER_SEC as u64;
1206        Duration::new(total_secs, total_nanos as u32)
1207    }};
1208}
1209
1210#[stable(feature = "duration_sum", since = "1.16.0")]
1211impl Sum for Duration {
1212    fn sum<I: Iterator<Item = Duration>>(iter: I) -> Duration {
1213        sum_durations!(iter)
1214    }
1215}
1216
1217#[stable(feature = "duration_sum", since = "1.16.0")]
1218impl<'a> Sum<&'a Duration> for Duration {
1219    fn sum<I: Iterator<Item = &'a Duration>>(iter: I) -> Duration {
1220        sum_durations!(iter)
1221    }
1222}
1223
1224#[stable(feature = "duration_debug_impl", since = "1.27.0")]
1225impl fmt::Debug for Duration {
1226    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1227        /// Formats a floating point number in decimal notation.
1228        ///
1229        /// The number is given as the `integer_part` and a fractional part.
1230        /// The value of the fractional part is `fractional_part / divisor`. So
1231        /// `integer_part` = 3, `fractional_part` = 12 and `divisor` = 100
1232        /// represents the number `3.012`. Trailing zeros are omitted.
1233        ///
1234        /// `divisor` must not be above 100_000_000. It also should be a power
1235        /// of 10, everything else doesn't make sense. `fractional_part` has
1236        /// to be less than `10 * divisor`!
1237        ///
1238        /// A prefix and postfix may be added. The whole thing is padded
1239        /// to the formatter's `width`, if specified.
1240        fn fmt_decimal(
1241            f: &mut fmt::Formatter<'_>,
1242            integer_part: u64,
1243            mut fractional_part: u32,
1244            mut divisor: u32,
1245            prefix: &str,
1246            postfix: &str,
1247        ) -> fmt::Result {
1248            // Encode the fractional part into a temporary buffer. The buffer
1249            // only need to hold 9 elements, because `fractional_part` has to
1250            // be smaller than 10^9. The buffer is prefilled with '0' digits
1251            // to simplify the code below.
1252            let mut buf = [b'0'; 9];
1253
1254            // The next digit is written at this position
1255            let mut pos = 0;
1256
1257            // We keep writing digits into the buffer while there are non-zero
1258            // digits left and we haven't written enough digits yet.
1259            while fractional_part > 0 && pos < f.precision().unwrap_or(9) {
1260                // Write new digit into the buffer
1261                buf[pos] = b'0' + (fractional_part / divisor) as u8;
1262
1263                fractional_part %= divisor;
1264                divisor /= 10;
1265                pos += 1;
1266            }
1267
1268            // If a precision < 9 was specified, there may be some non-zero
1269            // digits left that weren't written into the buffer. In that case we
1270            // need to perform rounding to match the semantics of printing
1271            // normal floating point numbers. However, we only need to do work
1272            // when rounding up. This happens if the first digit of the
1273            // remaining ones is >= 5.
1274            let integer_part = if fractional_part > 0 && fractional_part >= divisor * 5 {
1275                // Round up the number contained in the buffer. We go through
1276                // the buffer backwards and keep track of the carry.
1277                let mut rev_pos = pos;
1278                let mut carry = true;
1279                while carry && rev_pos > 0 {
1280                    rev_pos -= 1;
1281
1282                    // If the digit in the buffer is not '9', we just need to
1283                    // increment it and can stop then (since we don't have a
1284                    // carry anymore). Otherwise, we set it to '0' (overflow)
1285                    // and continue.
1286                    if buf[rev_pos] < b'9' {
1287                        buf[rev_pos] += 1;
1288                        carry = false;
1289                    } else {
1290                        buf[rev_pos] = b'0';
1291                    }
1292                }
1293
1294                // If we still have the carry bit set, that means that we set
1295                // the whole buffer to '0's and need to increment the integer
1296                // part.
1297                if carry {
1298                    // If `integer_part == u64::MAX` and precision < 9, any
1299                    // carry of the overflow during rounding of the
1300                    // `fractional_part` into the `integer_part` will cause the
1301                    // `integer_part` itself to overflow. Avoid this by using an
1302                    // `Option<u64>`, with `None` representing `u64::MAX + 1`.
1303                    integer_part.checked_add(1)
1304                } else {
1305                    Some(integer_part)
1306                }
1307            } else {
1308                Some(integer_part)
1309            };
1310
1311            // Determine the end of the buffer: if precision is set, we just
1312            // use as many digits from the buffer (capped to 9). If it isn't
1313            // set, we only use all digits up to the last non-zero one.
1314            let end = f.precision().map(|p| crate::cmp::min(p, 9)).unwrap_or(pos);
1315
1316            // This closure emits the formatted duration without emitting any
1317            // padding (padding is calculated below).
1318            let emit_without_padding = |f: &mut fmt::Formatter<'_>| {
1319                if let Some(integer_part) = integer_part {
1320                    write!(f, "{}{}", prefix, integer_part)?;
1321                } else {
1322                    // u64::MAX + 1 == 18446744073709551616
1323                    write!(f, "{}18446744073709551616", prefix)?;
1324                }
1325
1326                // Write the decimal point and the fractional part (if any).
1327                if end > 0 {
1328                    // SAFETY: We are only writing ASCII digits into the buffer and
1329                    // it was initialized with '0's, so it contains valid UTF8.
1330                    let s = unsafe { crate::str::from_utf8_unchecked(&buf[..end]) };
1331
1332                    // If the user request a precision > 9, we pad '0's at the end.
1333                    let w = f.precision().unwrap_or(pos);
1334                    write!(f, ".{:0<width$}", s, width = w)?;
1335                }
1336
1337                write!(f, "{}", postfix)
1338            };
1339
1340            match f.width() {
1341                None => {
1342                    // No `width` specified. There's no need to calculate the
1343                    // length of the output in this case, just emit it.
1344                    emit_without_padding(f)
1345                }
1346                Some(requested_w) => {
1347                    // A `width` was specified. Calculate the actual width of
1348                    // the output in order to calculate the required padding.
1349                    // It consists of 4 parts:
1350                    // 1. The prefix: is either "+" or "", so we can just use len().
1351                    // 2. The postfix: can be "µs" so we have to count UTF8 characters.
1352                    let mut actual_w = prefix.len() + postfix.chars().count();
1353                    // 3. The integer part:
1354                    if let Some(integer_part) = integer_part {
1355                        if let Some(log) = integer_part.checked_ilog10() {
1356                            // integer_part is > 0, so has length log10(x)+1
1357                            actual_w += 1 + log as usize;
1358                        } else {
1359                            // integer_part is 0, so has length 1.
1360                            actual_w += 1;
1361                        }
1362                    } else {
1363                        // integer_part is u64::MAX + 1, so has length 20
1364                        actual_w += 20;
1365                    }
1366                    // 4. The fractional part (if any):
1367                    if end > 0 {
1368                        let frac_part_w = f.precision().unwrap_or(pos);
1369                        actual_w += 1 + frac_part_w;
1370                    }
1371
1372                    if requested_w <= actual_w {
1373                        // Output is already longer than `width`, so don't pad.
1374                        emit_without_padding(f)
1375                    } else {
1376                        // We need to add padding. Use the `Formatter::padding` helper function.
1377                        let default_align = fmt::Alignment::Left;
1378                        let post_padding = f.padding(requested_w - actual_w, default_align)?;
1379                        emit_without_padding(f)?;
1380                        post_padding.write(f)
1381                    }
1382                }
1383            }
1384        }
1385
1386        // Print leading '+' sign if requested
1387        let prefix = if f.sign_plus() { "+" } else { "" };
1388
1389        if self.secs > 0 {
1390            fmt_decimal(f, self.secs, self.nanos.as_inner(), NANOS_PER_SEC / 10, prefix, "s")
1391        } else if self.nanos.as_inner() >= NANOS_PER_MILLI {
1392            fmt_decimal(
1393                f,
1394                (self.nanos.as_inner() / NANOS_PER_MILLI) as u64,
1395                self.nanos.as_inner() % NANOS_PER_MILLI,
1396                NANOS_PER_MILLI / 10,
1397                prefix,
1398                "ms",
1399            )
1400        } else if self.nanos.as_inner() >= NANOS_PER_MICRO {
1401            fmt_decimal(
1402                f,
1403                (self.nanos.as_inner() / NANOS_PER_MICRO) as u64,
1404                self.nanos.as_inner() % NANOS_PER_MICRO,
1405                NANOS_PER_MICRO / 10,
1406                prefix,
1407                "µs",
1408            )
1409        } else {
1410            fmt_decimal(f, self.nanos.as_inner() as u64, 0, 1, prefix, "ns")
1411        }
1412    }
1413}
1414
1415/// An error which can be returned when converting a floating-point value of seconds
1416/// into a [`Duration`].
1417///
1418/// This error is used as the error type for [`Duration::try_from_secs_f32`] and
1419/// [`Duration::try_from_secs_f64`].
1420///
1421/// # Example
1422///
1423/// ```
1424/// use std::time::Duration;
1425///
1426/// if let Err(e) = Duration::try_from_secs_f32(-1.0) {
1427///     println!("Failed conversion to Duration: {e}");
1428/// }
1429/// ```
1430#[derive(Debug, Clone, PartialEq, Eq)]
1431#[stable(feature = "duration_checked_float", since = "1.66.0")]
1432pub struct TryFromFloatSecsError {
1433    kind: TryFromFloatSecsErrorKind,
1434}
1435
1436impl TryFromFloatSecsError {
1437    const fn description(&self) -> &'static str {
1438        match self.kind {
1439            TryFromFloatSecsErrorKind::Negative => {
1440                "cannot convert float seconds to Duration: value is negative"
1441            }
1442            TryFromFloatSecsErrorKind::OverflowOrNan => {
1443                "cannot convert float seconds to Duration: value is either too big or NaN"
1444            }
1445        }
1446    }
1447}
1448
1449#[stable(feature = "duration_checked_float", since = "1.66.0")]
1450impl fmt::Display for TryFromFloatSecsError {
1451    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1452        self.description().fmt(f)
1453    }
1454}
1455
1456#[derive(Debug, Clone, PartialEq, Eq)]
1457enum TryFromFloatSecsErrorKind {
1458    // Value is negative.
1459    Negative,
1460    // Value is either too big to be represented as `Duration` or `NaN`.
1461    OverflowOrNan,
1462}
1463
1464macro_rules! try_from_secs {
1465    (
1466        secs = $secs: expr,
1467        mantissa_bits = $mant_bits: literal,
1468        exponent_bits = $exp_bits: literal,
1469        offset = $offset: literal,
1470        bits_ty = $bits_ty:ty,
1471        double_ty = $double_ty:ty,
1472    ) => {{
1473        const MIN_EXP: i16 = 1 - (1i16 << $exp_bits) / 2;
1474        const MANT_MASK: $bits_ty = (1 << $mant_bits) - 1;
1475        const EXP_MASK: $bits_ty = (1 << $exp_bits) - 1;
1476
1477        if $secs < 0.0 {
1478            return Err(TryFromFloatSecsError { kind: TryFromFloatSecsErrorKind::Negative });
1479        }
1480
1481        let bits = $secs.to_bits();
1482        let mant = (bits & MANT_MASK) | (MANT_MASK + 1);
1483        let exp = ((bits >> $mant_bits) & EXP_MASK) as i16 + MIN_EXP;
1484
1485        let (secs, nanos) = if exp < -31 {
1486            // the input represents less than 1ns and can not be rounded to it
1487            (0u64, 0u32)
1488        } else if exp < 0 {
1489            // the input is less than 1 second
1490            let t = <$double_ty>::from(mant) << ($offset + exp);
1491            let nanos_offset = $mant_bits + $offset;
1492            let nanos_tmp = u128::from(NANOS_PER_SEC) * u128::from(t);
1493            let nanos = (nanos_tmp >> nanos_offset) as u32;
1494
1495            let rem_mask = (1 << nanos_offset) - 1;
1496            let rem_msb_mask = 1 << (nanos_offset - 1);
1497            let rem = nanos_tmp & rem_mask;
1498            let is_tie = rem == rem_msb_mask;
1499            let is_even = (nanos & 1) == 0;
1500            let rem_msb = nanos_tmp & rem_msb_mask == 0;
1501            let add_ns = !(rem_msb || (is_even && is_tie));
1502
1503            // f32 does not have enough precision to trigger the second branch
1504            // since it can not represent numbers between 0.999_999_940_395 and 1.0.
1505            let nanos = nanos + add_ns as u32;
1506            if ($mant_bits == 23) || (nanos != NANOS_PER_SEC) { (0, nanos) } else { (1, 0) }
1507        } else if exp < $mant_bits {
1508            let secs = u64::from(mant >> ($mant_bits - exp));
1509            let t = <$double_ty>::from((mant << exp) & MANT_MASK);
1510            let nanos_offset = $mant_bits;
1511            let nanos_tmp = <$double_ty>::from(NANOS_PER_SEC) * t;
1512            let nanos = (nanos_tmp >> nanos_offset) as u32;
1513
1514            let rem_mask = (1 << nanos_offset) - 1;
1515            let rem_msb_mask = 1 << (nanos_offset - 1);
1516            let rem = nanos_tmp & rem_mask;
1517            let is_tie = rem == rem_msb_mask;
1518            let is_even = (nanos & 1) == 0;
1519            let rem_msb = nanos_tmp & rem_msb_mask == 0;
1520            let add_ns = !(rem_msb || (is_even && is_tie));
1521
1522            // f32 does not have enough precision to trigger the second branch.
1523            // For example, it can not represent numbers between 1.999_999_880...
1524            // and 2.0. Bigger values result in even smaller precision of the
1525            // fractional part.
1526            let nanos = nanos + add_ns as u32;
1527            if ($mant_bits == 23) || (nanos != NANOS_PER_SEC) {
1528                (secs, nanos)
1529            } else {
1530                (secs + 1, 0)
1531            }
1532        } else if exp < 64 {
1533            // the input has no fractional part
1534            let secs = u64::from(mant) << (exp - $mant_bits);
1535            (secs, 0)
1536        } else {
1537            return Err(TryFromFloatSecsError { kind: TryFromFloatSecsErrorKind::OverflowOrNan });
1538        };
1539
1540        Ok(Duration::new(secs, nanos))
1541    }};
1542}
1543
1544impl Duration {
1545    /// The checked version of [`from_secs_f32`].
1546    ///
1547    /// [`from_secs_f32`]: Duration::from_secs_f32
1548    ///
1549    /// This constructor will return an `Err` if `secs` is negative, overflows `Duration` or not finite.
1550    ///
1551    /// # Examples
1552    /// ```
1553    /// use std::time::Duration;
1554    ///
1555    /// let res = Duration::try_from_secs_f32(0.0);
1556    /// assert_eq!(res, Ok(Duration::new(0, 0)));
1557    /// let res = Duration::try_from_secs_f32(1e-20);
1558    /// assert_eq!(res, Ok(Duration::new(0, 0)));
1559    /// let res = Duration::try_from_secs_f32(4.2e-7);
1560    /// assert_eq!(res, Ok(Duration::new(0, 420)));
1561    /// let res = Duration::try_from_secs_f32(2.7);
1562    /// assert_eq!(res, Ok(Duration::new(2, 700_000_048)));
1563    /// let res = Duration::try_from_secs_f32(3e10);
1564    /// assert_eq!(res, Ok(Duration::new(30_000_001_024, 0)));
1565    /// // subnormal float:
1566    /// let res = Duration::try_from_secs_f32(f32::from_bits(1));
1567    /// assert_eq!(res, Ok(Duration::new(0, 0)));
1568    ///
1569    /// let res = Duration::try_from_secs_f32(-5.0);
1570    /// assert!(res.is_err());
1571    /// let res = Duration::try_from_secs_f32(f32::NAN);
1572    /// assert!(res.is_err());
1573    /// let res = Duration::try_from_secs_f32(2e19);
1574    /// assert!(res.is_err());
1575    ///
1576    /// // the conversion uses rounding with tie resolution to even
1577    /// let res = Duration::try_from_secs_f32(0.999e-9);
1578    /// assert_eq!(res, Ok(Duration::new(0, 1)));
1579    ///
1580    /// // this float represents exactly 976562.5e-9
1581    /// let val = f32::from_bits(0x3A80_0000);
1582    /// let res = Duration::try_from_secs_f32(val);
1583    /// assert_eq!(res, Ok(Duration::new(0, 976_562)));
1584    ///
1585    /// // this float represents exactly 2929687.5e-9
1586    /// let val = f32::from_bits(0x3B40_0000);
1587    /// let res = Duration::try_from_secs_f32(val);
1588    /// assert_eq!(res, Ok(Duration::new(0, 2_929_688)));
1589    ///
1590    /// // this float represents exactly 1.000_976_562_5
1591    /// let val = f32::from_bits(0x3F802000);
1592    /// let res = Duration::try_from_secs_f32(val);
1593    /// assert_eq!(res, Ok(Duration::new(1, 976_562)));
1594    ///
1595    /// // this float represents exactly 1.002_929_687_5
1596    /// let val = f32::from_bits(0x3F806000);
1597    /// let res = Duration::try_from_secs_f32(val);
1598    /// assert_eq!(res, Ok(Duration::new(1, 2_929_688)));
1599    /// ```
1600    #[stable(feature = "duration_checked_float", since = "1.66.0")]
1601    #[inline]
1602    pub fn try_from_secs_f32(secs: f32) -> Result<Duration, TryFromFloatSecsError> {
1603        try_from_secs!(
1604            secs = secs,
1605            mantissa_bits = 23,
1606            exponent_bits = 8,
1607            offset = 41,
1608            bits_ty = u32,
1609            double_ty = u64,
1610        )
1611    }
1612
1613    /// The checked version of [`from_secs_f64`].
1614    ///
1615    /// [`from_secs_f64`]: Duration::from_secs_f64
1616    ///
1617    /// This constructor will return an `Err` if `secs` is negative, overflows `Duration` or not finite.
1618    ///
1619    /// # Examples
1620    /// ```
1621    /// use std::time::Duration;
1622    ///
1623    /// let res = Duration::try_from_secs_f64(0.0);
1624    /// assert_eq!(res, Ok(Duration::new(0, 0)));
1625    /// let res = Duration::try_from_secs_f64(1e-20);
1626    /// assert_eq!(res, Ok(Duration::new(0, 0)));
1627    /// let res = Duration::try_from_secs_f64(4.2e-7);
1628    /// assert_eq!(res, Ok(Duration::new(0, 420)));
1629    /// let res = Duration::try_from_secs_f64(2.7);
1630    /// assert_eq!(res, Ok(Duration::new(2, 700_000_000)));
1631    /// let res = Duration::try_from_secs_f64(3e10);
1632    /// assert_eq!(res, Ok(Duration::new(30_000_000_000, 0)));
1633    /// // subnormal float
1634    /// let res = Duration::try_from_secs_f64(f64::from_bits(1));
1635    /// assert_eq!(res, Ok(Duration::new(0, 0)));
1636    ///
1637    /// let res = Duration::try_from_secs_f64(-5.0);
1638    /// assert!(res.is_err());
1639    /// let res = Duration::try_from_secs_f64(f64::NAN);
1640    /// assert!(res.is_err());
1641    /// let res = Duration::try_from_secs_f64(2e19);
1642    /// assert!(res.is_err());
1643    ///
1644    /// // the conversion uses rounding with tie resolution to even
1645    /// let res = Duration::try_from_secs_f64(0.999e-9);
1646    /// assert_eq!(res, Ok(Duration::new(0, 1)));
1647    /// let res = Duration::try_from_secs_f64(0.999_999_999_499);
1648    /// assert_eq!(res, Ok(Duration::new(0, 999_999_999)));
1649    /// let res = Duration::try_from_secs_f64(0.999_999_999_501);
1650    /// assert_eq!(res, Ok(Duration::new(1, 0)));
1651    /// let res = Duration::try_from_secs_f64(42.999_999_999_499);
1652    /// assert_eq!(res, Ok(Duration::new(42, 999_999_999)));
1653    /// let res = Duration::try_from_secs_f64(42.999_999_999_501);
1654    /// assert_eq!(res, Ok(Duration::new(43, 0)));
1655    ///
1656    /// // this float represents exactly 976562.5e-9
1657    /// let val = f64::from_bits(0x3F50_0000_0000_0000);
1658    /// let res = Duration::try_from_secs_f64(val);
1659    /// assert_eq!(res, Ok(Duration::new(0, 976_562)));
1660    ///
1661    /// // this float represents exactly 2929687.5e-9
1662    /// let val = f64::from_bits(0x3F68_0000_0000_0000);
1663    /// let res = Duration::try_from_secs_f64(val);
1664    /// assert_eq!(res, Ok(Duration::new(0, 2_929_688)));
1665    ///
1666    /// // this float represents exactly 1.000_976_562_5
1667    /// let val = f64::from_bits(0x3FF0_0400_0000_0000);
1668    /// let res = Duration::try_from_secs_f64(val);
1669    /// assert_eq!(res, Ok(Duration::new(1, 976_562)));
1670    ///
1671    /// // this float represents exactly 1.002_929_687_5
1672    /// let val = f64::from_bits(0x3_FF00_C000_0000_000);
1673    /// let res = Duration::try_from_secs_f64(val);
1674    /// assert_eq!(res, Ok(Duration::new(1, 2_929_688)));
1675    /// ```
1676    #[stable(feature = "duration_checked_float", since = "1.66.0")]
1677    #[inline]
1678    pub fn try_from_secs_f64(secs: f64) -> Result<Duration, TryFromFloatSecsError> {
1679        try_from_secs!(
1680            secs = secs,
1681            mantissa_bits = 52,
1682            exponent_bits = 11,
1683            offset = 44,
1684            bits_ty = u64,
1685            double_ty = u128,
1686        )
1687    }
1688}