util: improve getStringWidth performance

BridgeAR · addaleax · commit 58cd76cb049f · 2020-09-22T19:54:05.000+02:00
This makes sure the common path does not normalize the input string. It's only required for characters that are outside of the ASCII range. Signed-off-by: Ruben Bridgewater <ruben@bridgewater.de> PR-URL: #33674 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
diff --git a/lib/internal/util/inspect.js b/lib/internal/util/inspect.js
@@ -1953,13 +1953,6 @@ function formatWithOptions(inspectOptions, ...args) {
   return str;
 }
 
-function prepareStringForGetStringWidth(str, removeControlChars) {
-  str = str.normalize('NFC');
-  if (removeControlChars)
-    str = stripVTControlCharacters(str);
-  return str;
-}
-
 if (internalBinding('config').hasIntl) {
   const icu = internalBinding('icu');
   // icu.getStringWidth(string, ambiguousAsFullWidth, expandEmojiSequence)
@@ -1970,13 +1963,14 @@ if (internalBinding('config').hasIntl) {
   getStringWidth = function getStringWidth(str, removeControlChars = true) {
     let width = 0;
 
-    str = prepareStringForGetStringWidth(str, removeControlChars);
+    if (removeControlChars)
+      str = stripVTControlCharacters(str);
     for (let i = 0; i < str.length; i++) {
       // Try to avoid calling into C++ by first handling the ASCII portion of
       // the string. If it is fully ASCII, we skip the C++ part.
       const code = str.charCodeAt(i);
       if (code >= 127) {
-        width += icu.getStringWidth(str.slice(i));
+        width += icu.getStringWidth(str.slice(i).normalize('NFC'));
         break;
       }
       width += code >= 32 ? 1 : 0;
@@ -1990,7 +1984,9 @@ if (internalBinding('config').hasIntl) {
   getStringWidth = function getStringWidth(str, removeControlChars = true) {
     let width = 0;
 
-    str = prepareStringForGetStringWidth(str, removeControlChars);
+    if (removeControlChars)
+      str = stripVTControlCharacters(str);
+    str = str.normalize('NFC');
     for (const char of str) {
       const code = char.codePointAt(0);
       if (isFullWidthCodePoint(code)) {
