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shuf: Tune performance for -i 1-1000000 #10478

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Merged
sylvestre merged 1 commit into from
Jan 25, 2026
+16 −7
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shuf: Tune performance for -i 1-1000000 #10478

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23 changes: 16 additions & 7 deletions src/uu/shuf/src/shuf.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -378,6 +378,7 @@ impl Writable for &OsStr {
}

impl Writable for u64 {
#[inline]
fn write_all_to(&self, output: &mut impl OsWrite) -> Result<(), Error> {
// The itoa crate is surprisingly much more efficient than a formatted write.
// It speeds up `shuf -r -n1000000 -i1-1024` by 1.8×.
Expand All @@ -386,13 +387,22 @@ impl Writable for u64 {
}
}

#[cold]
#[inline(never)]
fn handle_write_error(e: std::io::Error) -> Box<dyn uucore::error::UError> {
use uucore::error::FromIo;
let ctx = translate!("shuf-error-write-failed");
e.map_err_context(move || ctx)
}

#[inline(never)]
fn shuf_exec(
input: &mut impl Shufable,
opts: &Options,
rng: &mut WrappedRng,
output: &mut BufWriter<Box<dyn OsWrite>>,
) -> UResult<()> {
let ctx = || translate!("shuf-error-write-failed");
let sep = [opts.sep];
if opts.repeat {
if input.is_empty() {
return Err(USimpleError::new(
Expand All @@ -402,20 +412,19 @@ fn shuf_exec(
}
for _ in 0..opts.head_count {
let r = input.choose(rng)?;

r.write_all_to(output).map_err_context(ctx)?;
output.write_all(&[opts.sep]).map_err_context(ctx)?;
r.write_all_to(output).map_err(handle_write_error)?;
output.write_all(&sep).map_err(handle_write_error)?;
}
} else {
let shuffled = input.partial_shuffle(rng, opts.head_count)?;

for r in shuffled {
let r = r?;
r.write_all_to(output).map_err_context(ctx)?;
output.write_all(&[opts.sep]).map_err_context(ctx)?;
r.write_all_to(output).map_err(handle_write_error)?;
output.write_all(&sep).map_err(handle_write_error)?;
}
}
output.flush().map_err_context(ctx)?;
output.flush().map_err(handle_write_error)?;

Ok(())
}
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