buffers: faster type check

Also add support for any TypedArray as target.

lib/buffer.js

@@ -204,9 +204,9 @@ function toInteger(n, defaultVal) {
 }
 
 function _copy(source, target, targetStart, sourceStart, sourceEnd) {
-  if (!isUint8Array(source))
+  if (!ArrayBuffer.isView(source))
     throw new ERR_INVALID_ARG_TYPE('source', ['Buffer', 'Uint8Array'], source);
-  if (!isUint8Array(target))
+  if (!ArrayBuffer.isView(target))
     throw new ERR_INVALID_ARG_TYPE('target', ['Buffer', 'Uint8Array'], target);
 
   if (targetStart === undefined) {
@@ -221,34 +221,34 @@ function _copy(source, target, targetStart, sourceStart, sourceEnd) {
     sourceStart = 0;
   } else {
     sourceStart = toInteger(sourceStart, 0);
-    if (sourceStart < 0 || sourceStart > source.length)
-      throw new ERR_OUT_OF_RANGE('sourceStart', `>= 0 && <= ${source.length}`, sourceStart);
+    if (sourceStart < 0 || sourceStart > source.byteLength)
+      throw new ERR_OUT_OF_RANGE('sourceStart', `>= 0 && <= ${source.byteLength}`, sourceStart);
   }
 
   if (sourceEnd === undefined) {
-    sourceEnd = source.length;
+    sourceEnd = source.byteLength;
   } else {
     sourceEnd = toInteger(sourceEnd, 0);
     if (sourceEnd < 0)
       throw new ERR_OUT_OF_RANGE('sourceEnd', '>= 0', sourceEnd);
   }
 
-  if (targetStart >= target.length || sourceStart >= sourceEnd)
+  if (targetStart >= target.byteLength || sourceStart >= sourceEnd)
     return 0;
 
   return _copyActual(source, target, targetStart, sourceStart, sourceEnd);
 }
 
 function _copyActual(source, target, targetStart, sourceStart, sourceEnd) {
-  if (sourceEnd - sourceStart > target.length - targetStart)
-    sourceEnd = sourceStart + target.length - targetStart;
+  if (sourceEnd - sourceStart > target.byteLength - targetStart)
+    sourceEnd = sourceStart + target.byteLength - targetStart;
 
   let nb = sourceEnd - sourceStart;
-  const sourceLen = source.length - sourceStart;
+  const sourceLen = source.byteLength - sourceStart;
   if (nb > sourceLen)
     nb = sourceLen;
 
-  if (sourceStart !== 0 || sourceEnd < source.length)
+  if (sourceStart !== 0 || sourceEnd < source.byteLength)
     source = new Uint8Array(source.buffer, source.byteOffset + sourceStart, nb);
 
   TypedArrayPrototypeSet(target, source, targetStart);