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Merge pull request #7495 from karlmcdowall/wc_perf

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wc: Perf gains with the bytecount crate.
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Sylvestre Ledru 2025-03-20 09:52:15 +01:00 • committed by GitHub
commit 187d3e58b5
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3 changed files with 6 additions and 13 deletions
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7
src/uu/wc/BENCHMARKING.md
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@ -26,10 +26,11 @@ output of uutils `cat` into it. Note that GNU `cat` is slower and therefore less
suitable, and that if a file is given as its input directly (as in
`wc -c < largefile`) the first strategy kicks in. Try `uucat somefile | wc -c`.
### Counting lines
### Counting lines and UTF-8 characters
In the case of `wc -l` or `wc -cl` the input doesn't have to be decoded. It's
read in chunks and the `bytecount` crate is used to count the newlines.
If the flags set are a subset of `-clm` then the input doesn't have to be decoded. The
input is read in chunks and the `bytecount` crate is used to count the newlines (`-l` flag)
and/or UTF-8 characters (`-m` flag).
It's useful to vary the line length in the input. GNU wc seems particularly
bad at short lines.

2
src/uu/wc/Cargo.toml
View file

@ -19,7 +19,7 @@ path = "src/wc.rs"
[dependencies]
clap = { workspace = true }
uucore = { workspace = true, features = ["pipes", "quoting-style"] }
bytecount = { workspace = true }
bytecount = { workspace = true, features = ["runtime-dispatch-simd"] }
thiserror = { workspace = true }
unicode-width = { workspace = true }

10
src/uu/wc/src/count_fast.rs
View file

@ -212,11 +212,6 @@ pub(crate) fn count_bytes_chars_and_lines_fast<
>(
handle: &mut R,
) -> (WordCount, Option<io::Error>) {
/// Mask of the value bits of a continuation byte
const CONT_MASK: u8 = 0b0011_1111u8;
/// Value of the tag bits (tag mask is !CONT_MASK) of a continuation byte
const TAG_CONT_U8: u8 = 0b1000_0000u8;
let mut total = WordCount::default();
let mut buf = [0; BUF_SIZE];
loop {
@ -227,10 +222,7 @@ pub(crate) fn count_bytes_chars_and_lines_fast<
total.bytes += n;
}
if COUNT_CHARS {
total.chars += buf[..n]
.iter()
.filter(|&&byte| (byte & !CONT_MASK) != TAG_CONT_U8)
.count();
total.chars += bytecount::num_chars(&buf[..n]);
}
if COUNT_LINES {
total.lines += bytecount::count(&buf[..n], b'\n');