fs: extract out validateBuffer function

PR-URL: #17682
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

lib/fs.js

@@ -153,6 +153,15 @@ function makeCallback(cb) {
   };
 }
 
+function validateBuffer(buffer) {
+  if (!isUint8Array(buffer)) {
+    const err = new errors.TypeError('ERR_INVALID_ARG_TYPE', 'buffer',
+                                     ['Buffer', 'Uint8Array']);
+    Error.captureStackTrace(err, validateBuffer);
+    throw err;
+  }
+}
+
 function validateFd(fd) {
   let err;
 
@@ -745,9 +754,7 @@ fs.openSync = function(path, flags, mode) {
 
 fs.read = function(fd, buffer, offset, length, position, callback) {
   validateFd(fd);
-  if (!isUint8Array(buffer))
-    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'buffer',
-                               ['Buffer', 'Uint8Array']);
+  validateBuffer(buffer);
 
   offset |= 0;
   length |= 0;
@@ -779,9 +786,7 @@ Object.defineProperty(fs.read, internalUtil.customPromisifyArgs,
 
 fs.readSync = function(fd, buffer, offset, length, position) {
   validateFd(fd);
-  if (!isUint8Array(buffer))
-    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'buffer',
-                               ['Buffer', 'Uint8Array']);
+  validateBuffer(buffer);
 
   offset |= 0;
   length |= 0;