add type check to set

Author: gurgunday

lib/buffer.js

@@ -240,7 +240,7 @@ function copyImpl(source, target, targetStart, sourceStart, sourceEnd) {
   return _copyActual(source, target, targetStart, sourceStart, sourceEnd);
 }
 
-function _copyActual(source, target, targetStart, sourceStart, sourceEnd) {
+function _copyActual(source, target, targetStart, sourceStart, sourceEnd, isUint8Copy = false) {
   if (sourceEnd - sourceStart > target.byteLength - targetStart)
     sourceEnd = sourceStart + target.byteLength - targetStart;
 
@@ -252,7 +252,7 @@ function _copyActual(source, target, targetStart, sourceStart, sourceEnd) {
   if (nb <= 0)
     return 0;
 
-  if (sourceStart === 0 && nb === sourceLen) {
+  if (sourceStart === 0 && nb === sourceLen && (isUint8Copy || isUint8Array(target))) {
     TypedArrayPrototypeSet(target, source, targetStart);
   } else {
     _copy(source, target, targetStart, sourceStart, nb);
@@ -604,7 +604,7 @@ Buffer.concat = function concat(list, length) {
       throw new ERR_INVALID_ARG_TYPE(
         `list[${i}]`, ['Buffer', 'Uint8Array'], list[i]);
     }
-    pos += _copyActual(buf, buffer, pos, 0, buf.length);
+    pos += _copyActual(buf, buffer, pos, 0, buf.length, true);
   }
 
   // Note: `length` is always equal to `buffer.length` at this point

test/parallel/test-buffer-copy.js

@@ -226,6 +226,16 @@ b.copy(c, 'not a valid offset');
 // Make sure this acted like a regular copy with `0` offset.
 assert.deepStrictEqual(c, b.slice(0, c.length));
 
+// Copy into a Uint16Array target; bytes are packed into 16-bit elements.
+{
+  const x = new Uint16Array(4);
+  const buf = Buffer.of(1, 2, 3, 4);
+  const copied = buf.copy(x);
+  assert.strictEqual(copied, 4);
+  assert.ok(x instanceof Uint16Array);
+  assert.deepStrictEqual(Array.from(x), [513, 1027, 0, 0]);
+}
+
 {
   c.fill('C');
   assert.throws(() => {