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wc: skip String to measure number length

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Sadly ilog10 isn't available until we use 1.67, but we can get close in
the meantime.
This commit is contained in:
Jed Denlea 2023-04-24 23:41:59 -07:00
parent 36b45e2249
commit d58ee5a28a
1 changed files with 35 additions and 2 deletions
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37
src/uu/wc/src/wc.rs
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@ -5,7 +5,7 @@
// * For the full copyright and license information, please view the LICENSE
// * file that was distributed with this source code.
// cSpell:ignore wc wc's
// cSpell:ignore ilog wc wc's
mod count_fast;
mod countable;
@ -632,7 +632,14 @@ fn compute_number_width(inputs: &[Input], settings: &Settings) -> usize {
}
}
max(minimum_width, total.to_string().len())
if total == 0 {
minimum_width
} else {
let total_width = (1 + ilog10_u64(total))
.try_into()
.expect("ilog of a u64 should fit into a usize");
max(total_width, minimum_width)
}
}
fn wc(inputs: &[Input], settings: &Settings) -> UResult<()> {
@ -712,3 +719,29 @@ fn print_stats(
writeln!(stdout)
}
}
// TODO: remove and just use usize::ilog10 once the MSRV is >= 1.67.
fn ilog10_u64(mut u: u64) -> u32 {
if u == 0 {
panic!("cannot compute log of 0")
}
let mut log = 0;
if u >= 10_000_000_000 {
log += 10;
u /= 10_000_000_000;
}
if u >= 100_000 {
log += 5;
u /= 100_000;
}
// Rust's standard library in versions >= 1.67 does something even more clever than this, but
// this should work just fine for the time being.
log + match u {
1..=9 => 0,
10..=99 => 1,
100..=999 => 2,
1000..=9999 => 3,
10000..=99999 => 4,
_ => unreachable!(),
}
}