Implement .forEach() on typed arrays

src/harmony-typedarray.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+'use strict';
+
+// This file relies on the fact that the following declaration has been made
+// in runtime.js:
+// var $Array = global.Array;
+
+// -------------------------------------------------------------------
+
+macro TYPED_ARRAYS(FUNCTION)
+// arrayIds below should be synchronized with Runtime_TypedArrayInitialize.
+FUNCTION(1, Uint8Array, 1)
+FUNCTION(2, Int8Array, 1)
+FUNCTION(3, Uint16Array, 2)
+FUNCTION(4, Int16Array, 2)
+FUNCTION(5, Uint32Array, 4)
+FUNCTION(6, Int32Array, 4)
+FUNCTION(7, Float32Array, 4)
+FUNCTION(8, Float64Array, 8)
+FUNCTION(9, Uint8ClampedArray, 1)
+endmacro
+
+
+macro TYPED_ARRAY_CONSTRUCTOR(ARRAY_ID, NAME, ELEMENT_SIZE)
+
+// ES6 draft 08-24-14, section 22.2.3.12
+function NAMEForEach(f /* thisArg */) {  // length == 1
+  if (!%IsTypedArray(this)) {

[wingo, 2014/10/07 11:18:44]

Normally you don't want runtime calls in the hot path of a function, because
they can't be optimized without special support in the compiler.  Is there not
another way to do this?

+    throw MakeTypeError('not_typed_array', []);
+  }
+  if (!IS_SPEC_FUNCTION(f)) {
+    throw MakeTypeError('called_non_callable', [ f ]);
+  }
+
+  var length = %_TypedArrayGetLength(this);
+  var receiver;
+
+  if (%_ArgumentsLength() > 1) {
+    receiver = %_Arguments(1);
+  }
+
+  if (IS_NULL_OR_UNDEFINED(receiver)) {
+    receiver = %GetDefaultReceiver(f) || receiver;
+  }
+  var needs_wrapper = SHOULD_CREATE_WRAPPER(f, receiver);

[wingo, 2014/10/07 11:18:44]

this needs to be in an "else" case; i.e.

var needs_wrapper = false;
if (IS_NULL_OR_UNDEFINED(receiver)) {
  ...
} else {
  needs_wrapper = SHOULD_CREATE_WRAPPER(f, receiver);
}

+
+  var stepping = DEBUG_IS_ACTIVE && %DebugCallbackSupportsStepping(f);
+  for (var i = 0; i < length; i++) {
+    var element = this[i];
+    // Prepare break slots for debugger step in.
+    if (stepping) %DebugPrepareStepInIfStepping(f);
+    var new_receiver = needs_wrapper ? ToObject(receiver) : receiver;
+    %_CallFunction(new_receiver, TO_OBJECT_INLINE(element), i, this, f);
+  }
+}
+endmacro
+
+TYPED_ARRAYS(TYPED_ARRAY_CONSTRUCTOR)
+
+
+function HarmonyTypedArrayExtendPrototypes() {
+macro EXTEND_TYPED_ARRAY(ARRAY_ID, NAME, ELEMENT_SIZE)
+  %CheckIsBootstrapping();
+
+  // Set up non-enumerable functions on the prototype object.
+  InstallFunctions(global.NAME.prototype, DONT_ENUM, $Array(
+    "forEach", NAMEForEach
+  ));
+endmacro
+
+  TYPED_ARRAYS(EXTEND_TYPED_ARRAY)
+}
+
+HarmonyTypedArrayExtendPrototypes();