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[rustdoc] a small performance improvement: only allocate new string if there are DOS backlines in highlight.rs #147443

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Merged
bors merged 1 commit into from
Oct 8, 2025
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[rustdoc] a small performance improvement: only allocate new string if there are DOS backlines in highlight.rs #147443

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8 changes: 7 additions & 1 deletion src/librustdoc/html/highlight.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -408,7 +408,13 @@ pub(super) fn write_code(
line_info: Option<LineInfo>,
) {
// This replace allows to fix how the code source with DOS backline characters is displayed.
let src = src.replace("\r\n", "\n");
let src =
// The first "\r\n" should be fairly close to the beginning of the string relatively
// to its overall length, and most strings handled by rustdoc likely don't have
// DOS backlines anyway.
// Checking for the single ASCII character '\r' is much more efficient than checking for
// the whole string "\r\n".
if src.contains('\r') { src.replace("\r\n", "\n").into() } else { Cow::Borrowed(src) };
let mut token_handler = TokenHandler {
out,
closing_tags: Vec::new(),
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