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fix nanos overflow for f64

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Артём Павлов [Artyom Pavlov] 2022-05-27 04:59:01 +03:00
parent 06af3a63a5
commit 38609cd8a9
1 changed files with 24 additions and 9 deletions
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33
library/core/src/time.rs
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@ -1288,12 +1288,14 @@ macro_rules! try_from_secs {
let rem_msb = nanos_tmp & rem_msb_mask == 0;
let add_ns = !(rem_msb || (is_even && is_tie));
// note that neither `f32`, nor `f64` can represent
// 0.999_999_999_5 exactly, so the nanos part
// never will be equal to NANOS_PER_SEC
// f32 does not have enough presicion to trigger the second branch
// since it can not represent numbers between 0.999_999_940_395 and 1.0.
let nanos = nanos + add_ns as u32;
debug_assert!(nanos < NANOS_PER_SEC);
(0, nanos)
if ($mant_bits == 23) || (nanos != NANOS_PER_SEC) {
(0, nanos)
} else {
(1, 0)
}
} else if exp < $mant_bits {
let secs = u64::from(mant >> ($mant_bits - exp));
let t = <$double_ty>::from((mant << exp) & MANT_MASK);
@ -1309,11 +1311,16 @@ macro_rules! try_from_secs {
let rem_msb = nanos_tmp & rem_msb_mask == 0;
let add_ns = !(rem_msb || (is_even && is_tie));
// neither `f32`, nor `f64` can represent x.999_999_999_5 exactly,
// so the nanos part never will be equal to NANOS_PER_SEC
// f32 does not have enough presicion to trigger the second branch.
// For example, it can not represent numbers between 1.999_999_880...
// and 2.0. Bigger values result in even smaller presicion of the
// fractional part.
let nanos = nanos + add_ns as u32;
debug_assert!(nanos < NANOS_PER_SEC);
(secs, nanos)
if ($mant_bits == 23) || (nanos != NANOS_PER_SEC) {
(secs, nanos)
} else {
(secs + 1, 0)
}
} else if exp < 64 {
// the input has no fractional part
let secs = u64::from(mant) << (exp - $mant_bits);
@ -1433,6 +1440,14 @@ impl Duration {
/// // the conversion uses rounding with tie resolution to even
/// let res = Duration::try_from_secs_f64(0.999e-9);
/// assert_eq!(res, Ok(Duration::new(0, 1)));
/// let res = Duration::try_from_secs_f64(0.999_999_999_499);
/// assert_eq!(res, Ok(Duration::new(0, 999_999_999)));
/// let res = Duration::try_from_secs_f64(0.999_999_999_501);
/// assert_eq!(res, Ok(Duration::new(1, 0)));
/// let res = Duration::try_from_secs_f64(42.999_999_999_499);
/// assert_eq!(res, Ok(Duration::new(42, 999_999_999)));
/// let res = Duration::try_from_secs_f64(42.999_999_999_501);
/// assert_eq!(res, Ok(Duration::new(43, 0)));
///
/// // this float represents exactly 976562.5e-9
/// let val = f64::from_bits(0x3F50_0000_0000_0000);