http: optimize checkIsHttpToken for short strings

Use lookup table instead of regex for strings shorter than 10
characters to improve performance for common short header names
while maintaining compatibility.

Author: JinhyeokFang

lib/_http_common.js

@@ -24,6 +24,7 @@
 const {
   MathMin,
   Symbol,
+  Uint8Array,
 } = primordials;
 const { setImmediate } = require('timers');
 
@@ -205,7 +206,37 @@ function freeParser(parser, req, socket) {
   }
 }
 
+// Character code ranges for valid HTTP tokens
+// Valid chars: ^_`a-zA-Z-0-9!#$%&'*+.|~
 const tokenRegExp = /^[\^_`a-zA-Z\-0-9!#$%&'*+.|~]+$/;
+const validTokenChars = new Uint8Array(256);
+
+// Initialize valid character lookup table
+(function initTokenChars() {
+  // a-z
+  for (let i = 97; i <= 122; i++) validTokenChars[i] = 1;
+  // A-Z
+  for (let i = 65; i <= 90; i++) validTokenChars[i] = 1;
+  // 0-9
+  for (let i = 48; i <= 57; i++) validTokenChars[i] = 1;
+  // Special chars: !#$%&'*+-.^_`|~
+  validTokenChars[33] = 1; // !
+  validTokenChars[35] = 1; // #
+  validTokenChars[36] = 1; // $
+  validTokenChars[37] = 1; // %
+  validTokenChars[38] = 1; // &
+  validTokenChars[39] = 1; // '
+  validTokenChars[42] = 1; // *
+  validTokenChars[43] = 1; // +
+  validTokenChars[45] = 1; // -
+  validTokenChars[46] = 1; // .
+  validTokenChars[94] = 1; // ^
+  validTokenChars[95] = 1; // _
+  validTokenChars[96] = 1; // `
+  validTokenChars[124] = 1; // |
+  validTokenChars[126] = 1; // ~
+})();
+
 /**
  * Verifies that the given val is a valid HTTP token
  * per the rules defined in RFC 7230
@@ -214,7 +245,19 @@ const tokenRegExp = /^[\^_`a-zA-Z\-0-9!#$%&'*+.|~]+$/;
  * @returns {boolean}
  */
 function checkIsHttpToken(val) {
-  return tokenRegExp.test(val);
+  if (val.length >= 10) {
+    return tokenRegExp.test(val);
+  }
+
+  if (val.length === 0) return false;
+
+  // Use lookup table for short strings, regex for longer ones
+  for (let i = 0; i < val.length; i++) {
+    if (!validTokenChars[val.charCodeAt(i)]) {
+      return false;
+    }
+  }
+  return true;
 }
 
 const headerCharRegex = /[^\t\x20-\x7e\x80-\xff]/;