1 files changed, 50 insertions, 27 deletions
diff --git a/lib/internal/util.js b/lib/internal/util.js
index 2516b84f34..b144063ee5 100644
--- a/lib/internal/util.js
+++ b/lib/internal/util.js
@@ -96,36 +96,59 @@ function assertCrypto() {
     throw new errors.Error('ERR_NO_CRYPTO');
 }
 
-// The loop should only run at most twice, retrying with lowercased enc
-// if there is no match in the first pass.
-// We use a loop instead of branching to retry with a helper
-// function in order to avoid the performance hit.
 // Return undefined if there is no match.
+// Move the "slow cases" to a separate function to make sure this function gets
+// inlined properly. That prioritizes the common case.
 function normalizeEncoding(enc) {
-  if (enc == null || enc === '') return 'utf8';
-  let retried;
-  while (true) {
-    switch (enc) {
-      case 'utf8':
-      case 'utf-8':
-        return 'utf8';
-      case 'ucs2':
-      case 'ucs-2':
-      case 'utf16le':
-      case 'utf-16le':
+  if (enc == null || enc === 'utf8' || enc === 'utf-8') return 'utf8';
+  return slowCases(enc);
+}
+
+function slowCases(enc) {
+  switch (enc.length) {
+    case 4:
+      if (enc === 'UTF8') return 'utf8';
+      if (enc === 'ucs2' || enc === 'UCS2') return 'utf16le';
+      enc = `${enc}`.toLowerCase();
+      if (enc === 'utf8') return 'utf8';
+      if (enc === 'ucs2' || enc === 'UCS2') return 'utf16le';
+      break;
+    case 3:
+      if (enc === 'hex' || enc === 'HEX' || `${enc}`.toLowerCase() === 'hex')
+        return 'hex';
+      break;
+    case 5:
+      if (enc === 'ascii') return 'ascii';
+      if (enc === 'ucs-2') return 'utf16le';
+      if (enc === 'UTF-8') return 'utf8';
+      if (enc === 'ASCII') return 'ascii';
+      if (enc === 'UCS-2') return 'utf16le';
+      enc = `${enc}`.toLowerCase();
+      if (enc === 'utf-8') return 'utf8';
+      if (enc === 'ascii') return 'ascii';
+      if (enc === 'usc-2') return 'utf16le';
+      break;
+    case 6:
+      if (enc === 'base64') return 'base64';
+      if (enc === 'latin1' || enc === 'binary') return 'latin1';
+      if (enc === 'BASE64') return 'base64';
+      if (enc === 'LATIN1' || enc === 'BINARY') return 'latin1';
+      enc = `${enc}`.toLowerCase();
+      if (enc === 'base64') return 'base64';
+      if (enc === 'latin1' || enc === 'binary') return 'latin1';
+      break;
+    case 7:
+      if (enc === 'utf16le' || enc === 'UTF16LE' ||
+        `${enc}`.toLowerCase() === 'utf16le')
         return 'utf16le';
-      case 'latin1':
-      case 'binary':
-        return 'latin1';
-      case 'base64':
-      case 'ascii':
-      case 'hex':
-        return enc;
-      default:
-        if (retried) return; // undefined
-        enc = ('' + enc).toLowerCase();
-        retried = true;
-    }
+      break;
+    case 8:
+      if (enc === 'utf-16le' || enc === 'UTF-16LE' ||
+        `${enc}`.toLowerCase() === 'utf-16le')
+        return 'utf16le';
+      break;
+    default:
+      if (enc === '') return 'utf8';
   }
 }