[minor] Use buffer.isUtf8() if possible

Closes #2110

README.md

@@ -58,9 +58,9 @@ npm install ws
 ### Opt-in for performance
 
 There are 2 optional modules that can be installed along side with the ws
-module. These modules are binary addons which improve certain operations.
-Prebuilt binaries are available for the most popular platforms so you don't
-necessarily need to have a C++ compiler installed on your machine.
+module. These modules are binary addons that improve the performance of certain
+operations. Prebuilt binaries are available for the most popular platforms so
+you don't necessarily need to have a C++ compiler installed on your machine.
 
 - `npm install --save-optional bufferutil`: Allows to efficiently perform
   operations such as masking and unmasking the data payload of the WebSocket
@@ -75,6 +75,10 @@ variables. These might be useful to enhance security in systems where a user can
 put a package in the package search path of an application of another user, due
 to how the Node.js resolver algorithm works.
 
+The `utf-8-validate` module is not needed and is not required, even if it is
+already installed, regardless of the value of the `WS_NO_UTF_8_VALIDATE`
+environment variable, if [`buffer.isUtf8()`][] is available.
+
 ## API docs
 
 See [`/doc/ws.md`](./doc/ws.md) for Node.js-like documentation of ws classes and
@@ -482,6 +486,7 @@ We're using the GitHub [releases][changelog] for changelog entries.
 
 [MIT](LICENSE)
 
+[`buffer.isutf8()`]: https://nodejs.org/api/buffer.html#bufferisutf8input
 [changelog]: https://github.com/websockets/ws/releases
 [client-report]: http://websockets.github.io/ws/autobahn/clients/
 [https-proxy-agent]: https://github.com/TooTallNate/node-https-proxy-agent

lib/validation.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const { isUtf8 } = require('buffer');
+
 //
 // Allowed token characters:
 //
@@ -111,13 +113,16 @@ module.exports = {
   tokenChars
 };
 
-/* istanbul ignore else  */
-if (!process.env.WS_NO_UTF_8_VALIDATE) {
+if (isUtf8) {
+  module.exports.isValidUTF8 = function (buf) {
+    return buf.length < 24 ? _isValidUTF8(buf) : isUtf8(buf);
+  };
+} /* istanbul ignore else  */ else if (!process.env.WS_NO_UTF_8_VALIDATE) {
   try {
     const isValidUTF8 = require('utf-8-validate');
 
     module.exports.isValidUTF8 = function (buf) {
-      return buf.length < 150 ? _isValidUTF8(buf) : isValidUTF8(buf);
+      return buf.length < 32 ? _isValidUTF8(buf) : isValidUTF8(buf);
     };
   } catch (e) {
     // Continue regardless of the error.