Skip to content

Commit

Permalink
Use rounding in float to Duration conversion methods
Browse files Browse the repository at this point in the history
  • Loading branch information
@newpavlov
newpavlov committed Apr 14, 2022
1 parent 563250a commit 65c75b2
Showing 1 changed file with 38 additions and 23 deletions.
61 changes: 38 additions & 23 deletions library/core/src/time.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -730,9 +730,9 @@ impl Duration {
/// // subnormal float
/// let res = Duration::from_secs_f64(f64::from_bits(1));
/// assert_eq!(res, Duration::new(0, 0));
/// // conversion uses truncation, not rounding
/// // conversion uses rounding
/// let res = Duration::from_secs_f64(0.999e-9);
/// assert_eq!(res, Duration::new(0, 0));
/// assert_eq!(res, Duration::new(0, 1));
/// ```
#[stable(feature = "duration_float", since = "1.38.0")]
#[must_use]
Expand Down Expand Up @@ -760,17 +760,17 @@ impl Duration {
/// let res = Duration::from_secs_f32(1e-20);
/// assert_eq!(res, Duration::new(0, 0));
/// let res = Duration::from_secs_f32(4.2e-7);
/// assert_eq!(res, Duration::new(0, 419));
/// assert_eq!(res, Duration::new(0, 420));
/// let res = Duration::from_secs_f32(2.7);
/// assert_eq!(res, Duration::new(2, 700_000_047));
/// assert_eq!(res, Duration::new(2, 700_000_048));
/// let res = Duration::from_secs_f32(3e10);
/// assert_eq!(res, Duration::new(30_000_001_024, 0));
/// // subnormal float
/// let res = Duration::from_secs_f32(f32::from_bits(1));
/// assert_eq!(res, Duration::new(0, 0));
/// // conversion uses truncation, not rounding
/// // conversion uses rounding
/// let res = Duration::from_secs_f32(0.999e-9);
/// assert_eq!(res, Duration::new(0, 0));
/// assert_eq!(res, Duration::new(0, 1));
/// ```
#[stable(feature = "duration_float", since = "1.38.0")]
#[must_use]
Expand Down Expand Up @@ -815,7 +815,7 @@ impl Duration {
/// use std::time::Duration;
///
/// let dur = Duration::new(2, 700_000_000);
/// assert_eq!(dur.mul_f32(3.14), Duration::new(8, 478_000_640));
/// assert_eq!(dur.mul_f32(3.14), Duration::new(8, 478_000_641));
/// assert_eq!(dur.mul_f32(3.14e5), Duration::new(847800, 0));
/// ```
#[stable(feature = "duration_float", since = "1.38.0")]
Expand All @@ -838,8 +838,7 @@ impl Duration {
///
/// let dur = Duration::new(2, 700_000_000);
/// assert_eq!(dur.div_f64(3.14), Duration::new(0, 859_872_611));
/// // note that truncation is used, not rounding
/// assert_eq!(dur.div_f64(3.14e5), Duration::new(0, 8_598));
/// assert_eq!(dur.div_f64(3.14e5), Duration::new(0, 8_599));
/// ```
#[stable(feature = "duration_float", since = "1.38.0")]
#[must_use = "this returns the result of the operation, \
Expand All @@ -862,9 +861,8 @@ impl Duration {
/// let dur = Duration::new(2, 700_000_000);
/// // note that due to rounding errors result is slightly
/// // different from 0.859_872_611
/// assert_eq!(dur.div_f32(3.14), Duration::new(0, 859_872_579));
/// // note that truncation is used, not rounding
/// assert_eq!(dur.div_f32(3.14e5), Duration::new(0, 8_598));
/// assert_eq!(dur.div_f32(3.14), Duration::new(0, 859_872_580));
/// assert_eq!(dur.div_f32(3.14e5), Duration::new(0, 8_599));
/// ```
#[stable(feature = "duration_float", since = "1.38.0")]
#[must_use = "this returns the result of the operation, \
Expand Down Expand Up @@ -1278,13 +1276,30 @@ macro_rules! try_from_secs {
} else if exp < 0 {
// the input is less than 1 second
let t = <$double_ty>::from(mant) << ($offset + exp);
let nanos = (u128::from(NANOS_PER_SEC) * u128::from(t)) >> ($mant_bits + $offset);
(0, nanos as u32)
let nanos_offset = $mant_bits + $offset;
let nanos_tmp = u128::from(NANOS_PER_SEC) * u128::from(t);
let nanos = (nanos_tmp >> nanos_offset) as u32;
if nanos_tmp & (1 << (nanos_offset - 1)) == 0 {
(0, nanos)
} else if nanos + 1 != NANOS_PER_SEC {
(0, nanos + 1)
} else {
(1, 0)
}
} else if exp < $mant_bits {
let secs = mant >> ($mant_bits - exp);
let secs = u64::from(mant >> ($mant_bits - exp));
let t = <$double_ty>::from((mant << exp) & MANT_MASK);
let nanos = (<$double_ty>::from(NANOS_PER_SEC) * t) >> $mant_bits;
(u64::from(secs), nanos as u32)
let nanos_tmp = <$double_ty>::from(NANOS_PER_SEC) * t;
let nanos = (nanos_tmp >> $mant_bits) as u32;
if nanos_tmp & (1 << ($mant_bits - 1)) == 0 {
(secs, nanos)
} else if nanos + 1 != NANOS_PER_SEC {
(secs, nanos + 1)
} else {
// `secs + 1` can not overflow since `exp` is less than `$mant_bits`
// and the latter is less than 64 bits for both `f32` and `f64`
(secs + 1, 0)
}
} else if exp < 64 {
// the input has no fractional part
let secs = u64::from(mant) << (exp - $mant_bits);
Expand Down Expand Up @@ -1315,17 +1330,17 @@ impl Duration {
/// let res = Duration::try_from_secs_f32(1e-20);
/// assert_eq!(res, Ok(Duration::new(0, 0)));
/// let res = Duration::try_from_secs_f32(4.2e-7);
/// assert_eq!(res, Ok(Duration::new(0, 419)));
/// assert_eq!(res, Ok(Duration::new(0, 420)));
/// let res = Duration::try_from_secs_f32(2.7);
/// assert_eq!(res, Ok(Duration::new(2, 700_000_047)));
/// assert_eq!(res, Ok(Duration::new(2, 700_000_048)));
/// let res = Duration::try_from_secs_f32(3e10);
/// assert_eq!(res, Ok(Duration::new(30_000_001_024, 0)));
/// // subnormal float:
/// let res = Duration::try_from_secs_f32(f32::from_bits(1));
/// assert_eq!(res, Ok(Duration::new(0, 0)));
/// // conversion uses truncation, not rounding
/// // conversion uses rounding
/// let res = Duration::try_from_secs_f32(0.999e-9);
/// assert_eq!(res, Ok(Duration::new(0, 0)));
/// assert_eq!(res, Ok(Duration::new(0, 1)));
///
/// let res = Duration::try_from_secs_f32(-5.0);
/// assert!(res.is_err());
Expand Down Expand Up @@ -1372,9 +1387,9 @@ impl Duration {
/// // subnormal float
/// let res = Duration::try_from_secs_f64(f64::from_bits(1));
/// assert_eq!(res, Ok(Duration::new(0, 0)));
/// // conversion uses truncation, not rounding
/// // conversion uses rounding
/// let res = Duration::try_from_secs_f32(0.999e-9);
/// assert_eq!(res, Ok(Duration::new(0, 0)));
/// assert_eq!(res, Ok(Duration::new(0, 1)));
///
/// let res = Duration::try_from_secs_f64(-5.0);
/// assert!(res.is_err());
Expand Down

0 comments on commit 65c75b2

Please sign in to comment.