1 #![stable(feature = "duration_core", since = "1.25.0")]
3 //! Temporal quantification.
8 //! use std::time::Duration;
10 //! let five_seconds = Duration::new(5, 0);
11 //! // both declarations are equivalent
12 //! assert_eq!(Duration::new(5, 0), Duration::from_secs(5));
16 use crate::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
17 use crate::{fmt, u64};
19 const NANOS_PER_SEC: u32 = 1_000_000_000;
20 const NANOS_PER_MILLI: u32 = 1_000_000;
21 const NANOS_PER_MICRO: u32 = 1_000;
22 const MILLIS_PER_SEC: u64 = 1_000;
23 const MICROS_PER_SEC: u64 = 1_000_000;
25 /// A `Duration` type to represent a span of time, typically used for system
28 /// Each `Duration` is composed of a whole number of seconds and a fractional part
29 /// represented in nanoseconds. If the underlying system does not support
30 /// nanosecond-level precision, APIs binding a system timeout will typically round up
31 /// the number of nanoseconds.
33 /// `Duration`s implement many common traits, including [`Add`], [`Sub`], and other
36 /// [`Add`]: ../../std/ops/trait.Add.html
37 /// [`Sub`]: ../../std/ops/trait.Sub.html
38 /// [`ops`]: ../../std/ops/index.html
43 /// use std::time::Duration;
45 /// let five_seconds = Duration::new(5, 0);
46 /// let five_seconds_and_five_nanos = five_seconds + Duration::new(0, 5);
48 /// assert_eq!(five_seconds_and_five_nanos.as_secs(), 5);
49 /// assert_eq!(five_seconds_and_five_nanos.subsec_nanos(), 5);
51 /// let ten_millis = Duration::from_millis(10);
53 #[stable(feature = "duration", since = "1.3.0")]
54 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
57 nanos: u32, // Always 0 <= nanos < NANOS_PER_SEC
61 /// The duration of one second.
66 /// #![feature(duration_constants)]
67 /// use std::time::Duration;
69 /// assert_eq!(Duration::SECOND, Duration::from_secs(1));
71 #[unstable(feature = "duration_constants", issue = "57391")]
72 pub const SECOND: Duration = Duration::from_secs(1);
74 /// The duration of one millisecond.
79 /// #![feature(duration_constants)]
80 /// use std::time::Duration;
82 /// assert_eq!(Duration::MILLISECOND, Duration::from_millis(1));
84 #[unstable(feature = "duration_constants", issue = "57391")]
85 pub const MILLISECOND: Duration = Duration::from_millis(1);
87 /// The duration of one microsecond.
92 /// #![feature(duration_constants)]
93 /// use std::time::Duration;
95 /// assert_eq!(Duration::MICROSECOND, Duration::from_micros(1));
97 #[unstable(feature = "duration_constants", issue = "57391")]
98 pub const MICROSECOND: Duration = Duration::from_micros(1);
100 /// The duration of one nanosecond.
105 /// #![feature(duration_constants)]
106 /// use std::time::Duration;
108 /// assert_eq!(Duration::NANOSECOND, Duration::from_nanos(1));
110 #[unstable(feature = "duration_constants", issue = "57391")]
111 pub const NANOSECOND: Duration = Duration::from_nanos(1);
113 /// Creates a new `Duration` from the specified number of whole seconds and
114 /// additional nanoseconds.
116 /// If the number of nanoseconds is greater than 1 billion (the number of
117 /// nanoseconds in a second), then it will carry over into the seconds provided.
121 /// This constructor will panic if the carry from the nanoseconds overflows
122 /// the seconds counter.
127 /// use std::time::Duration;
129 /// let five_seconds = Duration::new(5, 0);
131 #[stable(feature = "duration", since = "1.3.0")]
133 pub fn new(secs: u64, nanos: u32) -> Duration {
135 secs.checked_add((nanos / NANOS_PER_SEC) as u64).expect("overflow in Duration::new");
136 let nanos = nanos % NANOS_PER_SEC;
137 Duration { secs, nanos }
140 /// Creates a new `Duration` from the specified number of whole seconds.
145 /// use std::time::Duration;
147 /// let duration = Duration::from_secs(5);
149 /// assert_eq!(5, duration.as_secs());
150 /// assert_eq!(0, duration.subsec_nanos());
152 #[stable(feature = "duration", since = "1.3.0")]
155 pub const fn from_secs(secs: u64) -> Duration {
156 Duration { secs, nanos: 0 }
159 /// Creates a new `Duration` from the specified number of milliseconds.
164 /// use std::time::Duration;
166 /// let duration = Duration::from_millis(2569);
168 /// assert_eq!(2, duration.as_secs());
169 /// assert_eq!(569_000_000, duration.subsec_nanos());
171 #[stable(feature = "duration", since = "1.3.0")]
174 pub const fn from_millis(millis: u64) -> Duration {
176 secs: millis / MILLIS_PER_SEC,
177 nanos: ((millis % MILLIS_PER_SEC) as u32) * NANOS_PER_MILLI,
181 /// Creates a new `Duration` from the specified number of microseconds.
186 /// use std::time::Duration;
188 /// let duration = Duration::from_micros(1_000_002);
190 /// assert_eq!(1, duration.as_secs());
191 /// assert_eq!(2000, duration.subsec_nanos());
193 #[stable(feature = "duration_from_micros", since = "1.27.0")]
196 pub const fn from_micros(micros: u64) -> Duration {
198 secs: micros / MICROS_PER_SEC,
199 nanos: ((micros % MICROS_PER_SEC) as u32) * NANOS_PER_MICRO,
203 /// Creates a new `Duration` from the specified number of nanoseconds.
208 /// use std::time::Duration;
210 /// let duration = Duration::from_nanos(1_000_000_123);
212 /// assert_eq!(1, duration.as_secs());
213 /// assert_eq!(123, duration.subsec_nanos());
215 #[stable(feature = "duration_extras", since = "1.27.0")]
218 pub const fn from_nanos(nanos: u64) -> Duration {
220 secs: nanos / (NANOS_PER_SEC as u64),
221 nanos: (nanos % (NANOS_PER_SEC as u64)) as u32,
225 /// Returns the number of _whole_ seconds contained by this `Duration`.
227 /// The returned value does not include the fractional (nanosecond) part of the
228 /// duration, which can be obtained using [`subsec_nanos`].
233 /// use std::time::Duration;
235 /// let duration = Duration::new(5, 730023852);
236 /// assert_eq!(duration.as_secs(), 5);
239 /// To determine the total number of seconds represented by the `Duration`,
240 /// use `as_secs` in combination with [`subsec_nanos`]:
243 /// use std::time::Duration;
245 /// let duration = Duration::new(5, 730023852);
247 /// assert_eq!(5.730023852,
248 /// duration.as_secs() as f64
249 /// + duration.subsec_nanos() as f64 * 1e-9);
252 /// [`subsec_nanos`]: #method.subsec_nanos
253 #[stable(feature = "duration", since = "1.3.0")]
255 pub const fn as_secs(&self) -> u64 {
259 /// Returns the fractional part of this `Duration`, in whole milliseconds.
261 /// This method does **not** return the length of the duration when
262 /// represented by milliseconds. The returned number always represents a
263 /// fractional portion of a second (i.e., it is less than one thousand).
268 /// use std::time::Duration;
270 /// let duration = Duration::from_millis(5432);
271 /// assert_eq!(duration.as_secs(), 5);
272 /// assert_eq!(duration.subsec_millis(), 432);
274 #[stable(feature = "duration_extras", since = "1.27.0")]
276 pub const fn subsec_millis(&self) -> u32 {
277 self.nanos / NANOS_PER_MILLI
280 /// Returns the fractional part of this `Duration`, in whole microseconds.
282 /// This method does **not** return the length of the duration when
283 /// represented by microseconds. The returned number always represents a
284 /// fractional portion of a second (i.e., it is less than one million).
289 /// use std::time::Duration;
291 /// let duration = Duration::from_micros(1_234_567);
292 /// assert_eq!(duration.as_secs(), 1);
293 /// assert_eq!(duration.subsec_micros(), 234_567);
295 #[stable(feature = "duration_extras", since = "1.27.0")]
297 pub const fn subsec_micros(&self) -> u32 {
298 self.nanos / NANOS_PER_MICRO
301 /// Returns the fractional part of this `Duration`, in nanoseconds.
303 /// This method does **not** return the length of the duration when
304 /// represented by nanoseconds. The returned number always represents a
305 /// fractional portion of a second (i.e., it is less than one billion).
310 /// use std::time::Duration;
312 /// let duration = Duration::from_millis(5010);
313 /// assert_eq!(duration.as_secs(), 5);
314 /// assert_eq!(duration.subsec_nanos(), 10_000_000);
316 #[stable(feature = "duration", since = "1.3.0")]
318 pub const fn subsec_nanos(&self) -> u32 {
322 /// Returns the total number of whole milliseconds contained by this `Duration`.
327 /// use std::time::Duration;
329 /// let duration = Duration::new(5, 730023852);
330 /// assert_eq!(duration.as_millis(), 5730);
332 #[stable(feature = "duration_as_u128", since = "1.33.0")]
334 pub const fn as_millis(&self) -> u128 {
335 self.secs as u128 * MILLIS_PER_SEC as u128 + (self.nanos / NANOS_PER_MILLI) as u128
338 /// Returns the total number of whole microseconds contained by this `Duration`.
343 /// use std::time::Duration;
345 /// let duration = Duration::new(5, 730023852);
346 /// assert_eq!(duration.as_micros(), 5730023);
348 #[stable(feature = "duration_as_u128", since = "1.33.0")]
350 pub const fn as_micros(&self) -> u128 {
351 self.secs as u128 * MICROS_PER_SEC as u128 + (self.nanos / NANOS_PER_MICRO) as u128
354 /// Returns the total number of nanoseconds contained by this `Duration`.
359 /// use std::time::Duration;
361 /// let duration = Duration::new(5, 730023852);
362 /// assert_eq!(duration.as_nanos(), 5730023852);
364 #[stable(feature = "duration_as_u128", since = "1.33.0")]
366 pub const fn as_nanos(&self) -> u128 {
367 self.secs as u128 * NANOS_PER_SEC as u128 + self.nanos as u128
370 /// Checked `Duration` addition. Computes `self + other`, returning [`None`]
371 /// if overflow occurred.
373 /// [`None`]: ../../std/option/enum.Option.html#variant.None
380 /// use std::time::Duration;
382 /// assert_eq!(Duration::new(0, 0).checked_add(Duration::new(0, 1)), Some(Duration::new(0, 1)));
383 /// assert_eq!(Duration::new(1, 0).checked_add(Duration::new(std::u64::MAX, 0)), None);
385 #[stable(feature = "duration_checked_ops", since = "1.16.0")]
387 pub fn checked_add(self, rhs: Duration) -> Option<Duration> {
388 if let Some(mut secs) = self.secs.checked_add(rhs.secs) {
389 let mut nanos = self.nanos + rhs.nanos;
390 if nanos >= NANOS_PER_SEC {
391 nanos -= NANOS_PER_SEC;
392 if let Some(new_secs) = secs.checked_add(1) {
398 debug_assert!(nanos < NANOS_PER_SEC);
399 Some(Duration { secs, nanos })
405 /// Checked `Duration` subtraction. Computes `self - other`, returning [`None`]
406 /// if the result would be negative or if overflow occurred.
408 /// [`None`]: ../../std/option/enum.Option.html#variant.None
415 /// use std::time::Duration;
417 /// assert_eq!(Duration::new(0, 1).checked_sub(Duration::new(0, 0)), Some(Duration::new(0, 1)));
418 /// assert_eq!(Duration::new(0, 0).checked_sub(Duration::new(0, 1)), None);
420 #[stable(feature = "duration_checked_ops", since = "1.16.0")]
422 pub fn checked_sub(self, rhs: Duration) -> Option<Duration> {
423 if let Some(mut secs) = self.secs.checked_sub(rhs.secs) {
424 let nanos = if self.nanos >= rhs.nanos {
425 self.nanos - rhs.nanos
427 if let Some(sub_secs) = secs.checked_sub(1) {
429 self.nanos + NANOS_PER_SEC - rhs.nanos
434 debug_assert!(nanos < NANOS_PER_SEC);
435 Some(Duration { secs, nanos })
441 /// Checked `Duration` multiplication. Computes `self * other`, returning
442 /// [`None`] if overflow occurred.
444 /// [`None`]: ../../std/option/enum.Option.html#variant.None
451 /// use std::time::Duration;
453 /// assert_eq!(Duration::new(0, 500_000_001).checked_mul(2), Some(Duration::new(1, 2)));
454 /// assert_eq!(Duration::new(std::u64::MAX - 1, 0).checked_mul(2), None);
456 #[stable(feature = "duration_checked_ops", since = "1.16.0")]
458 pub fn checked_mul(self, rhs: u32) -> Option<Duration> {
459 // Multiply nanoseconds as u64, because it cannot overflow that way.
460 let total_nanos = self.nanos as u64 * rhs as u64;
461 let extra_secs = total_nanos / (NANOS_PER_SEC as u64);
462 let nanos = (total_nanos % (NANOS_PER_SEC as u64)) as u32;
464 self.secs.checked_mul(rhs as u64).and_then(|s| s.checked_add(extra_secs))
466 debug_assert!(nanos < NANOS_PER_SEC);
467 Some(Duration { secs, nanos })
473 /// Checked `Duration` division. Computes `self / other`, returning [`None`]
476 /// [`None`]: ../../std/option/enum.Option.html#variant.None
483 /// use std::time::Duration;
485 /// assert_eq!(Duration::new(2, 0).checked_div(2), Some(Duration::new(1, 0)));
486 /// assert_eq!(Duration::new(1, 0).checked_div(2), Some(Duration::new(0, 500_000_000)));
487 /// assert_eq!(Duration::new(2, 0).checked_div(0), None);
489 #[stable(feature = "duration_checked_ops", since = "1.16.0")]
491 pub fn checked_div(self, rhs: u32) -> Option<Duration> {
493 let secs = self.secs / (rhs as u64);
494 let carry = self.secs - secs * (rhs as u64);
495 let extra_nanos = carry * (NANOS_PER_SEC as u64) / (rhs as u64);
496 let nanos = self.nanos / rhs + (extra_nanos as u32);
497 debug_assert!(nanos < NANOS_PER_SEC);
498 Some(Duration { secs, nanos })
504 /// Returns the number of seconds contained by this `Duration` as `f64`.
506 /// The returned value does include the fractional (nanosecond) part of the duration.
510 /// use std::time::Duration;
512 /// let dur = Duration::new(2, 700_000_000);
513 /// assert_eq!(dur.as_secs_f64(), 2.7);
515 #[stable(feature = "duration_float", since = "1.38.0")]
517 pub fn as_secs_f64(&self) -> f64 {
518 (self.secs as f64) + (self.nanos as f64) / (NANOS_PER_SEC as f64)
521 /// Returns the number of seconds contained by this `Duration` as `f32`.
523 /// The returned value does include the fractional (nanosecond) part of the duration.
527 /// use std::time::Duration;
529 /// let dur = Duration::new(2, 700_000_000);
530 /// assert_eq!(dur.as_secs_f32(), 2.7);
532 #[stable(feature = "duration_float", since = "1.38.0")]
534 pub fn as_secs_f32(&self) -> f32 {
535 (self.secs as f32) + (self.nanos as f32) / (NANOS_PER_SEC as f32)
538 /// Creates a new `Duration` from the specified number of seconds represented
542 /// This constructor will panic if `secs` is not finite, negative or overflows `Duration`.
546 /// use std::time::Duration;
548 /// let dur = Duration::from_secs_f64(2.7);
549 /// assert_eq!(dur, Duration::new(2, 700_000_000));
551 #[stable(feature = "duration_float", since = "1.38.0")]
553 pub fn from_secs_f64(secs: f64) -> Duration {
554 const MAX_NANOS_F64: f64 = ((u64::MAX as u128 + 1) * (NANOS_PER_SEC as u128)) as f64;
555 let nanos = secs * (NANOS_PER_SEC as f64);
556 if !nanos.is_finite() {
557 panic!("got non-finite value when converting float to duration");
559 if nanos >= MAX_NANOS_F64 {
560 panic!("overflow when converting float to duration");
563 panic!("underflow when converting float to duration");
565 let nanos = nanos as u128;
567 secs: (nanos / (NANOS_PER_SEC as u128)) as u64,
568 nanos: (nanos % (NANOS_PER_SEC as u128)) as u32,
572 /// Creates a new `Duration` from the specified number of seconds represented
576 /// This constructor will panic if `secs` is not finite, negative or overflows `Duration`.
580 /// use std::time::Duration;
582 /// let dur = Duration::from_secs_f32(2.7);
583 /// assert_eq!(dur, Duration::new(2, 700_000_000));
585 #[stable(feature = "duration_float", since = "1.38.0")]
587 pub fn from_secs_f32(secs: f32) -> Duration {
588 const MAX_NANOS_F32: f32 = ((u64::MAX as u128 + 1) * (NANOS_PER_SEC as u128)) as f32;
589 let nanos = secs * (NANOS_PER_SEC as f32);
590 if !nanos.is_finite() {
591 panic!("got non-finite value when converting float to duration");
593 if nanos >= MAX_NANOS_F32 {
594 panic!("overflow when converting float to duration");
597 panic!("underflow when converting float to duration");
599 let nanos = nanos as u128;
601 secs: (nanos / (NANOS_PER_SEC as u128)) as u64,
602 nanos: (nanos % (NANOS_PER_SEC as u128)) as u32,
606 /// Multiplies `Duration` by `f64`.
609 /// This method will panic if result is not finite, negative or overflows `Duration`.
613 /// use std::time::Duration;
615 /// let dur = Duration::new(2, 700_000_000);
616 /// assert_eq!(dur.mul_f64(3.14), Duration::new(8, 478_000_000));
617 /// assert_eq!(dur.mul_f64(3.14e5), Duration::new(847_800, 0));
619 #[stable(feature = "duration_float", since = "1.38.0")]
621 pub fn mul_f64(self, rhs: f64) -> Duration {
622 Duration::from_secs_f64(rhs * self.as_secs_f64())
625 /// Multiplies `Duration` by `f32`.
628 /// This method will panic if result is not finite, negative or overflows `Duration`.
632 /// use std::time::Duration;
634 /// let dur = Duration::new(2, 700_000_000);
635 /// // note that due to rounding errors result is slightly different
636 /// // from 8.478 and 847800.0
637 /// assert_eq!(dur.mul_f32(3.14), Duration::new(8, 478_000_640));
638 /// assert_eq!(dur.mul_f32(3.14e5), Duration::new(847799, 969_120_256));
640 #[stable(feature = "duration_float", since = "1.38.0")]
642 pub fn mul_f32(self, rhs: f32) -> Duration {
643 Duration::from_secs_f32(rhs * self.as_secs_f32())
646 /// Divide `Duration` by `f64`.
649 /// This method will panic if result is not finite, negative or overflows `Duration`.
653 /// use std::time::Duration;
655 /// let dur = Duration::new(2, 700_000_000);
656 /// assert_eq!(dur.div_f64(3.14), Duration::new(0, 859_872_611));
657 /// // note that truncation is used, not rounding
658 /// assert_eq!(dur.div_f64(3.14e5), Duration::new(0, 8_598));
660 #[stable(feature = "duration_float", since = "1.38.0")]
662 pub fn div_f64(self, rhs: f64) -> Duration {
663 Duration::from_secs_f64(self.as_secs_f64() / rhs)
666 /// Divide `Duration` by `f32`.
669 /// This method will panic if result is not finite, negative or overflows `Duration`.
673 /// use std::time::Duration;
675 /// let dur = Duration::new(2, 700_000_000);
676 /// // note that due to rounding errors result is slightly
677 /// // different from 0.859_872_611
678 /// assert_eq!(dur.div_f32(3.14), Duration::new(0, 859_872_576));
679 /// // note that truncation is used, not rounding
680 /// assert_eq!(dur.div_f32(3.14e5), Duration::new(0, 8_598));
682 #[stable(feature = "duration_float", since = "1.38.0")]
684 pub fn div_f32(self, rhs: f32) -> Duration {
685 Duration::from_secs_f32(self.as_secs_f32() / rhs)
688 /// Divide `Duration` by `Duration` and return `f64`.
692 /// #![feature(div_duration)]
693 /// use std::time::Duration;
695 /// let dur1 = Duration::new(2, 700_000_000);
696 /// let dur2 = Duration::new(5, 400_000_000);
697 /// assert_eq!(dur1.div_duration_f64(dur2), 0.5);
699 #[unstable(feature = "div_duration", issue = "63139")]
701 pub fn div_duration_f64(self, rhs: Duration) -> f64 {
702 self.as_secs_f64() / rhs.as_secs_f64()
705 /// Divide `Duration` by `Duration` and return `f32`.
709 /// #![feature(div_duration)]
710 /// use std::time::Duration;
712 /// let dur1 = Duration::new(2, 700_000_000);
713 /// let dur2 = Duration::new(5, 400_000_000);
714 /// assert_eq!(dur1.div_duration_f32(dur2), 0.5);
716 #[unstable(feature = "div_duration", issue = "63139")]
718 pub fn div_duration_f32(self, rhs: Duration) -> f32 {
719 self.as_secs_f32() / rhs.as_secs_f32()
723 #[stable(feature = "duration", since = "1.3.0")]
724 impl Add for Duration {
725 type Output = Duration;
727 fn add(self, rhs: Duration) -> Duration {
728 self.checked_add(rhs).expect("overflow when adding durations")
732 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
733 impl AddAssign for Duration {
734 fn add_assign(&mut self, rhs: Duration) {
739 #[stable(feature = "duration", since = "1.3.0")]
740 impl Sub for Duration {
741 type Output = Duration;
743 fn sub(self, rhs: Duration) -> Duration {
744 self.checked_sub(rhs).expect("overflow when subtracting durations")
748 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
749 impl SubAssign for Duration {
750 fn sub_assign(&mut self, rhs: Duration) {
755 #[stable(feature = "duration", since = "1.3.0")]
756 impl Mul<u32> for Duration {
757 type Output = Duration;
759 fn mul(self, rhs: u32) -> Duration {
760 self.checked_mul(rhs).expect("overflow when multiplying duration by scalar")
764 #[stable(feature = "symmetric_u32_duration_mul", since = "1.31.0")]
765 impl Mul<Duration> for u32 {
766 type Output = Duration;
768 fn mul(self, rhs: Duration) -> Duration {
773 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
774 impl MulAssign<u32> for Duration {
775 fn mul_assign(&mut self, rhs: u32) {
780 #[stable(feature = "duration", since = "1.3.0")]
781 impl Div<u32> for Duration {
782 type Output = Duration;
784 fn div(self, rhs: u32) -> Duration {
785 self.checked_div(rhs).expect("divide by zero error when dividing duration by scalar")
789 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
790 impl DivAssign<u32> for Duration {
791 fn div_assign(&mut self, rhs: u32) {
796 macro_rules! sum_durations {
798 let mut total_secs: u64 = 0;
799 let mut total_nanos: u64 = 0;
803 total_secs.checked_add(entry.secs).expect("overflow in iter::sum over durations");
804 total_nanos = match total_nanos.checked_add(entry.nanos as u64) {
807 total_secs = total_secs
808 .checked_add(total_nanos / NANOS_PER_SEC as u64)
809 .expect("overflow in iter::sum over durations");
810 (total_nanos % NANOS_PER_SEC as u64) + entry.nanos as u64
814 total_secs = total_secs
815 .checked_add(total_nanos / NANOS_PER_SEC as u64)
816 .expect("overflow in iter::sum over durations");
817 total_nanos = total_nanos % NANOS_PER_SEC as u64;
818 Duration { secs: total_secs, nanos: total_nanos as u32 }
822 #[stable(feature = "duration_sum", since = "1.16.0")]
823 impl Sum for Duration {
824 fn sum<I: Iterator<Item = Duration>>(iter: I) -> Duration {
829 #[stable(feature = "duration_sum", since = "1.16.0")]
830 impl<'a> Sum<&'a Duration> for Duration {
831 fn sum<I: Iterator<Item = &'a Duration>>(iter: I) -> Duration {
836 #[stable(feature = "duration_debug_impl", since = "1.27.0")]
837 impl fmt::Debug for Duration {
838 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
839 /// Formats a floating point number in decimal notation.
841 /// The number is given as the `integer_part` and a fractional part.
842 /// The value of the fractional part is `fractional_part / divisor`. So
843 /// `integer_part` = 3, `fractional_part` = 12 and `divisor` = 100
844 /// represents the number `3.012`. Trailing zeros are omitted.
846 /// `divisor` must not be above 100_000_000. It also should be a power
847 /// of 10, everything else doesn't make sense. `fractional_part` has
848 /// to be less than `10 * divisor`!
850 f: &mut fmt::Formatter<'_>,
851 mut integer_part: u64,
852 mut fractional_part: u32,
855 // Encode the fractional part into a temporary buffer. The buffer
856 // only need to hold 9 elements, because `fractional_part` has to
857 // be smaller than 10^9. The buffer is prefilled with '0' digits
858 // to simplify the code below.
859 let mut buf = [b'0'; 9];
861 // The next digit is written at this position
864 // We keep writing digits into the buffer while there are non-zero
865 // digits left and we haven't written enough digits yet.
866 while fractional_part > 0 && pos < f.precision().unwrap_or(9) {
867 // Write new digit into the buffer
868 buf[pos] = b'0' + (fractional_part / divisor) as u8;
870 fractional_part %= divisor;
875 // If a precision < 9 was specified, there may be some non-zero
876 // digits left that weren't written into the buffer. In that case we
877 // need to perform rounding to match the semantics of printing
878 // normal floating point numbers. However, we only need to do work
879 // when rounding up. This happens if the first digit of the
880 // remaining ones is >= 5.
881 if fractional_part > 0 && fractional_part >= divisor * 5 {
882 // Round up the number contained in the buffer. We go through
883 // the buffer backwards and keep track of the carry.
884 let mut rev_pos = pos;
885 let mut carry = true;
886 while carry && rev_pos > 0 {
889 // If the digit in the buffer is not '9', we just need to
890 // increment it and can stop then (since we don't have a
891 // carry anymore). Otherwise, we set it to '0' (overflow)
893 if buf[rev_pos] < b'9' {
901 // If we still have the carry bit set, that means that we set
902 // the whole buffer to '0's and need to increment the integer
909 // Determine the end of the buffer: if precision is set, we just
910 // use as many digits from the buffer (capped to 9). If it isn't
911 // set, we only use all digits up to the last non-zero one.
912 let end = f.precision().map(|p| crate::cmp::min(p, 9)).unwrap_or(pos);
914 // If we haven't emitted a single fractional digit and the precision
915 // wasn't set to a non-zero value, we don't print the decimal point.
917 write!(f, "{}", integer_part)
919 // SAFETY: We are only writing ASCII digits into the buffer and it was
920 // initialized with '0's, so it contains valid UTF8.
921 let s = unsafe { crate::str::from_utf8_unchecked(&buf[..end]) };
923 // If the user request a precision > 9, we pad '0's at the end.
924 let w = f.precision().unwrap_or(pos);
925 write!(f, "{}.{:0<width$}", integer_part, s, width = w)
929 // Print leading '+' sign if requested
935 fmt_decimal(f, self.secs, self.nanos, 100_000_000)?;
937 } else if self.nanos >= 1_000_000 {
938 fmt_decimal(f, self.nanos as u64 / 1_000_000, self.nanos % 1_000_000, 100_000)?;
940 } else if self.nanos >= 1_000 {
941 fmt_decimal(f, self.nanos as u64 / 1_000, self.nanos % 1_000, 100)?;
944 fmt_decimal(f, self.nanos as u64, 0, 1)?;