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uucore: num_parser: Clarify origin of pow_with_context

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And why we use an older minimum Rust version in that piece of code.
This commit is contained in:
Nicolas Boichat 2025-06-01 19:27:06 +02:00
parent 5e3284139c
commit c5b445f6f2
1 changed files with 3 additions and 0 deletions
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3
src/uucore/src/lib/features/parser/num_parser.rs
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@ -384,6 +384,8 @@ fn make_error<'a>(overflow: bool, negative: bool) -> ExtendedParserError<'a, Ext
//
// TODO: Still pending discussion in https://github.com/akubera/bigdecimal-rs/issues/147,
// we do lose a little bit of precision, and the last digits may not be correct.
// Note: This has been copied from the latest revision in https://github.com/akubera/bigdecimal-rs/pull/148,
// so it's using minimum Rust version of `bigdecimal-rs`.
fn pow_with_context(bd: &BigDecimal, exp: i64, ctx: &Context) -> BigDecimal {
if exp == 0 {
return 1.into();
@ -412,6 +414,7 @@ fn pow_with_context(bd: &BigDecimal, exp: i64, ctx: &Context) -> BigDecimal {
// Note: 63 - n.leading_zeros() == n.ilog2, but that's only available in recent Rust versions.
let muls = (n.count_ones() + (63 - n.leading_zeros()) - 1) as u64;
// Note: div_ceil would be nice to use here, but only available in recent Rust versions.
// (see note above about minimum Rust version in use)
let margin_extra = (muls + MUL_PER_MARGIN_EXTRA / 2) / MUL_PER_MARGIN_EXTRA;
let mut margin = margin_extra + MARGIN_PER_MUL * muls;