os: improve network interface performance

This reduces the overhead of getCIDR() to a minimum. No array is
allocated anymore and parts are directly sliced out of the netmask
string instead.

Signed-off-by: Ruben Bridgewater <ruben@bridgewater.de>
PR-URL: #46598
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/os.js

@@ -28,7 +28,6 @@ const {
   ObjectDefineProperties,
   StringPrototypeEndsWith,
   StringPrototypeSlice,
-  StringPrototypeSplit,
   SymbolToPrimitive,
 } = primordials;
 
@@ -225,28 +224,38 @@ function getCIDR(address, netmask, family) {
   let range = 10;
   let groupLength = 8;
   let hasZeros = false;
+  let lastPos = 0;
 
   if (family === 'IPv6') {
     split = ':';
     range = 16;
     groupLength = 16;
   }
 
-  const parts = StringPrototypeSplit(netmask, split);
-  for (let i = 0; i < parts.length; i++) {
-    if (parts[i] !== '') {
-      const binary = NumberParseInt(parts[i], range);
-      const tmp = countBinaryOnes(binary);
-      ones += tmp;
+  for (let i = 0; i < netmask.length; i++) {
+    if (netmask[i] !== split) {
+      if (i + 1 < netmask.length) {
+        continue;
+      }
+      i++;
+    }
+    const part = StringPrototypeSlice(netmask, lastPos, i);
+    lastPos = i + 1;
+    if (part !== '') {
       if (hasZeros) {
-        if (tmp !== 0) {
+        if (part !== '0') {
           return null;
         }
-      } else if (tmp !== groupLength) {
-        if ((binary & 1) !== 0) {
-          return null;
+      } else {
+        const binary = NumberParseInt(part, range);
+        const binaryOnes = countBinaryOnes(binary);
+        ones += binaryOnes;
+        if (binaryOnes !== groupLength) {
+          if ((binary & 1) !== 0) {
+            return null;
+          }
+          hasZeros = true;
         }
-        hasZeros = true;
       }
     }
   }