From 35d45c2a4fead953654ae7bcf029cdf6d2590121 Mon Sep 17 00:00:00 2001
From: Luigi Pinca <luigipinca@gmail.com>
Date: Sun, 19 Dec 2021 20:49:13 +0100
Subject: [PATCH] [perf] Skip masking and unmasking if the masking key is zero

---
 lib/receiver.js        |  8 +++++++-
 lib/sender.js          | 32 ++++++++++++++++++++++----------
 test/websocket.test.js | 11 +++++++----
 3 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/lib/receiver.js b/lib/receiver.js
index e11e26618..2d29d62bb 100644
--- a/lib/receiver.js
+++ b/lib/receiver.js
@@ -417,7 +417,13 @@ class Receiver extends Writable {
       }
 
       data = this.consume(this._payloadLength);
-      if (this._masked) unmask(data, this._mask);
+
+      if (
+        this._masked &&
+        (this._mask[0] | this._mask[1] | this._mask[2] | this._mask[3]) !== 0
+      ) {
+        unmask(data, this._mask);
+      }
     }
 
     if (this._opcode > 0x07) return this.controlMessage(data);
diff --git a/lib/sender.js b/lib/sender.js
index 82cc662d6..2417656d7 100644
--- a/lib/sender.js
+++ b/lib/sender.js
@@ -65,8 +65,26 @@ class Sender {
    * @public
    */
   static frame(data, options) {
-    const merge = options.mask && options.readOnly;
-    let offset = options.mask ? 6 : 2;
+    let mask;
+    let merge = false;
+    let offset = 2;
+    let skipMasking = false;
+
+    if (options.mask) {
+      mask = options.maskBuffer || maskBuffer;
+
+      if (options.generateMask) {
+        options.generateMask(mask);
+      } else {
+        randomFillSync(mask, 0, 4);
+      }
+
+      skipMasking = (mask[0] | mask[1] | mask[2] | mask[3]) === 0;
+      if (options.readOnly && !skipMasking) merge = true;
+
+      offset = 6;
+    }
+
     let payloadLength = data.length;
 
     if (data.length >= 65536) {
@@ -93,20 +111,14 @@ class Sender {
 
     if (!options.mask) return [target, data];
 
-    const mask = options.maskBuffer ? options.maskBuffer : maskBuffer;
-
-    if (options.generateMask) {
-      options.generateMask(mask);
-    } else {
-      randomFillSync(mask, 0, 4);
-    }
-
     target[1] |= 0x80;
     target[offset - 4] = mask[0];
     target[offset - 3] = mask[1];
     target[offset - 2] = mask[2];
     target[offset - 1] = mask[3];
 
+    if (skipMasking) return [target, data];
+
     if (merge) {
       applyMask(data, mask, target, offset, data.length);
       return [target];
diff --git a/test/websocket.test.js b/test/websocket.test.js
index 5f9392d84..16cb33c55 100644
--- a/test/websocket.test.js
+++ b/test/websocket.test.js
@@ -128,13 +128,14 @@ describe('WebSocket', () => {
       });
 
       it('honors the `generateMask` option', (done) => {
+        const data = Buffer.from('foo');
         const wss = new WebSocket.Server({ port: 0 }, () => {
           const ws = new WebSocket(`ws://localhost:${wss.address().port}`, {
             generateMask() {}
           });
 
           ws.on('open', () => {
-            ws.send('foo');
+            ws.send(data);
           });
 
           ws.on('close', (code, reason) => {
@@ -152,9 +153,11 @@ describe('WebSocket', () => {
             chunks.push(chunk);
           });
 
-          ws.on('message', () => {
-            assert.ok(
-              Buffer.concat(chunks).slice(2, 6).equals(Buffer.alloc(4))
+          ws.on('message', (message) => {
+            assert.deepStrictEqual(message, data);
+            assert.deepStrictEqual(
+              Buffer.concat(chunks).slice(2, 6),
+              Buffer.alloc(4)
             );
 
             ws.close();