From ed47077736f6fdf797aa45de9e0516da5b99e690 Mon Sep 17 00:00:00 2001
From: Mert Can Altin <mertgold60@gmail.com>
Date: Sat, 27 Dec 2025 03:40:39 +0300
Subject: [PATCH] util: optimize toASCIILower function using V8s native
 toLowerCase

PR-URL: https://github.com/nodejs/node/pull/61107
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
---
 lib/internal/mime.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/internal/mime.js b/lib/internal/mime.js
index efe6a2212b0..de691a74503 100644
--- a/lib/internal/mime.js
+++ b/lib/internal/mime.js
@@ -23,6 +23,8 @@ const END_BEGINNING_WHITESPACE = /[^\r\n\t ]|$/;
 const START_ENDING_WHITESPACE = /[\r\n\t ]*$/;
 
 function toASCIILower(str) {
+  // eslint-disable-next-line no-control-regex
+  if (!/[^\x00-\x7f]/.test(str)) return StringPrototypeToLowerCase(str);
   let result = '';
   for (let i = 0; i < str.length; i++) {
     const char = str[i];