From 38ee88e2b6e9e84f55e3bcd140d81b2505720f0f Mon Sep 17 00:00:00 2001
From: crowlbot <280062030+crowlbot@users.noreply.github.com>
Date: Mon, 13 Jul 2026 10:57:05 +0000
Subject: [PATCH] perf: bulk-copy path segments in to_file_path (unix)

file_url_segments_to_pathbuf decoded each path segment with the
byte-at-a-time percent_decode iterator even when the segment contained
no '%'. Use the Cow<[u8]> bulk path instead: it borrows the segment
unchanged in the common no-escape case, so segments are copied with a
single extend_from_slice rather than pushed byte by byte.

Bench (parse_url/url_to_file_path): 135 -> 105 ns/iter (-22%).
---
 url/src/lib.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/url/src/lib.rs b/url/src/lib.rs
index fa2803681..10acaa941 100644
--- a/url/src/lib.rs
+++ b/url/src/lib.rs
@@ -3086,7 +3086,11 @@ fn file_url_segments_to_pathbuf(
 
     for segment in segments {
         bytes.push(b'/');
-        bytes.extend(percent_decode(segment.as_bytes()));
+        // `percent_decode(..).into()` yields a `Cow::Borrowed` when the segment
+        // has nothing to decode (no `%`), which is the common case; copying the
+        // slice in bulk is much faster than the byte-at-a-time decode iterator.
+        let decoded: Cow<'_, [u8]> = percent_decode(segment.as_bytes()).into();
+        bytes.extend_from_slice(&decoded);
     }
 
     // A windows drive letter must end with a slash.