os: improve networkInterfaces performance

This algorithm uses less data transformations and is therefore
significantly faster than the one before.

PR-URL: https://github.com/nodejs/node/pull/22359
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

1 files changed, 57 insertions, 10 deletions

diff --git a/lib/os.js b/lib/os.js
index 08daa182e8..e65c11fc58 100644
--- a/lib/os.js
+++ b/lib/os.js
@@ -24,7 +24,6 @@
 const { pushValToArrayMax, safeGetenv } = process.binding('util');
 const constants = process.binding('constants').os;
 const { deprecate } = require('internal/util');
-const { getCIDRSuffix } = require('internal/os');
 const isWindows = process.platform === 'win32';
 
 const { ERR_SYSTEM_ERROR } = require('internal/errors');
@@ -144,19 +143,67 @@ function endianness() {
 }
 endianness[Symbol.toPrimitive] = () => kEndianness;
 
+// Returns the number of ones in the binary representation of the decimal
+// number.
+function countBinaryOnes(n) {
+  let count = 0;
+  // Remove one "1" bit from n until n is the power of 2. This iterates k times
+  // while k is the number of "1" in the binary representation.
+  // For more check https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators
+  while (n !== 0) {
+    n = n & (n - 1);
+    count++;
+  }
+  return count;
+}
+
+function getCIDR({ address, netmask, family }) {
+  let ones = 0;
+  let split = '.';
+  let range = 10;
+  let groupLength = 8;
+  let hasZeros = false;
+
+  if (family === 'IPv6') {
+    split = ':';
+    range = 16;
+    groupLength = 16;
+  }
+
+  const parts = netmask.split(split);
+  for (var i = 0; i < parts.length; i++) {
+    if (parts[i] !== '') {
+      const binary = parseInt(parts[i], range);
+      const tmp = countBinaryOnes(binary);
+      ones += tmp;
+      if (hasZeros) {
+        if (tmp !== 0) {
+          return null;
+        }
+      } else if (tmp !== groupLength) {
+        if ((binary & 1) !== 0) {
+          return null;
+        }
+        hasZeros = true;
+      }
+    }
+  }
+
+  return `${address}/${ones}`;
+}
+
 function networkInterfaces() {
   const interfaceAddresses = getInterfaceAddresses();
 
-  return Object.entries(interfaceAddresses).reduce((acc, [key, val]) => {
-    acc[key] = val.map((v) => {
-      const protocol = v.family.toLowerCase();
-      const suffix = getCIDRSuffix(v.netmask, protocol);
-      const cidr = suffix ? `${v.address}/${suffix}` : null;
+  const keys = Object.keys(interfaceAddresses);
+  for (var i = 0; i < keys.length; i++) {
+    const arr = interfaceAddresses[keys[i]];
+    for (var j = 0; j < arr.length; j++) {
+      arr[j].cidr = getCIDR(arr[j]);
+    }
+  }
 
-      return Object.assign({}, v, { cidr });
-    });
-    return acc;
-  }, {});
+  return interfaceAddresses;
 }
 
 module.exports = {