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uucore: num_parser: Improve scale conversion to i64

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It turns out repeatedly calling i64::MAX.into() and i64::MIN.into()
is actually very expensive. Just do the conversion first, and if
it fails, we know why.

Sadly there is still a conversion happening under the hood in
`-exponent + scale`, but that'd need to be fixed in Bigint.

Improves sort -g performance by ~5%.
This commit is contained in:
Nicolas Boichat 2025-06-03 09:21:35 +02:00
parent 8426c1480c
commit edc1e5def6
1 changed files with 6 additions and 7 deletions
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13
src/uucore/src/lib/features/parser/num_parser.rs
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@ -465,16 +465,15 @@ fn construct_extended_big_decimal<'a>(
let bd = if scale == 0 && exponent.is_zero() {
BigDecimal::from_bigint(signed_digits, 0)
} else if base == Base::Decimal {
let new_scale = BigInt::from(scale) - exponent;
let new_scale = -exponent + scale;
// BigDecimal "only" supports i64 scale.
// Note that new_scale is a negative exponent: large value causes an underflow, small value an overflow.
if new_scale > i64::MAX.into() {
return Err(make_error(false, negative));
} else if new_scale < i64::MIN.into() {
return Err(make_error(true, negative));
// Note that new_scale is a negative exponent: large positive value causes an underflow, large negative values an overflow.
if let Some(new_scale) = new_scale.to_i64() {
BigDecimal::from_bigint(signed_digits, new_scale)
} else {
return Err(make_error(new_scale.is_negative(), negative));
}
BigDecimal::from_bigint(signed_digits, new_scale.to_i64().unwrap())
} else if base == Base::Hexadecimal {
// pow "only" supports u32 values, just error out if given more than 2**32 fractional digits.
if scale > u32::MAX.into() {