TypedArray.prototype.copyWithin method

src/harmony-typedarray.js

Index: src/harmony-typedarray.js
diff --git a/src/harmony-typedarray.js b/src/harmony-typedarray.js
index 5b666b5645f09a676b2cf8606f0f5a7b16d266dc..a163355e854f3322db61d821d5fe682bec55b12b 100644
--- a/src/harmony-typedarray.js
+++ b/src/harmony-typedarray.js
@@ -10,29 +10,77 @@
 
 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)
+FUNCTION(Uint8Array)
+FUNCTION(Int8Array)
+FUNCTION(Uint16Array)
+FUNCTION(Int16Array)
+FUNCTION(Uint32Array)
+FUNCTION(Int32Array)
+FUNCTION(Float32Array)
+FUNCTION(Float64Array)
+FUNCTION(Uint8ClampedArray)
 endmacro
 
-macro DECLARE_GLOBALS(INDEX, NAME, SIZE)
+macro DECLARE_GLOBALS(NAME)
 var GlobalNAME = global.NAME;
 endmacro
 
 TYPED_ARRAYS(DECLARE_GLOBALS)
 
-// -------------------------------------------------------------------
+// ES6 draft 03-17-15, section 22.2.3.5
+function TypedArrayCopyWithin(target, start, end) {
+  if (!%IsTypedArray(this)) {
+    throw MakeTypeError('not_typed_array', []);
+  }
+
+  var length = %_TypedArrayGetLength(this);
+
+  target = TO_INTEGER(target);
+  var to;
+  if (target < 0) {
+    to = $max(length + target, 0);
+  } else {
+    to = $min(target, length);
+  }
+
+  start = TO_INTEGER(start);
+  var from;
+  if (start < 0) {
+    from = $max(length + start, 0);
+  } else {
+    from = $min(start, length);
+  }
+
+  end = IS_UNDEFINED(end) ? length : TO_INTEGER(end);
+  var final;
+  if (end < 0) {
+    final = $max(length + end, 0);
+  } else {
+    final = $min(end, length);
+  }
+
+  var count = $min(final - from, length - to);
+  var direction = 1;
+  if (from < to && to < (from + count)) {
+    direction = -1;
+    from = from + count - 1;
+    to = to + count - 1;
+  }
 
-macro TYPED_ARRAY_HARMONY_ADDITIONS(ARRAY_ID, NAME, ELEMENT_SIZE)
+  while (count > 0) {
+    this[to] = this[from];

[caitp (gmail), 2015/05/07 20:13:20]

This is a pretty good first implementation.

Might be worth leaving a TODO comment about doing it all with MemMove(), not
sure

[adamk, 2015/05/07 20:28:07]

To expand on this a bit, is there any reason not to re-use the code for
Array.prototype.copyWithin here? This comment likely applies to many of these
methods, at least until optimized versions are written.

+    from = from + direction;
+    to = to + direction;
+    count--;
+  }
+
+  return this;
+}
+
+// -------------------------------------------------------------------
 
 // ES6 draft 05-05-15, section 22.2.3.7
-function NAMEEvery(f /* thisArg */) {  // length == 1
+function TypedArrayEvery(f /* thisArg */) {  // length == 1

[caitp (gmail), 2015/05/07 20:13:20]

Moving the rest of these outside the macro is good, but I'm not sure it's in
scope for this CL. No strong opinion on that though

   if (!%IsTypedArray(this)) {
     throw MakeTypeError('not_typed_array', []);
   }
@@ -66,7 +114,7 @@ function NAMEEvery(f /* thisArg */) {  // length == 1
 }
 
 // ES6 draft 08-24-14, section 22.2.3.12
-function NAMEForEach(f /* thisArg */) {  // length == 1
+function TypedArrayForEach(f /* thisArg */) {  // length == 1
   if (!%IsTypedArray(this)) throw MakeTypeError(kNotTypedArray);
   if (!IS_SPEC_FUNCTION(f)) throw MakeTypeError(kCalledNonCallable, f);
 
@@ -95,7 +143,7 @@ function NAMEForEach(f /* thisArg */) {  // length == 1
 }
 
 // ES6 draft 08-24-14, section 22.2.2.2
-function NAMEOf() {  // length == 0
+function TypedArrayOf() {  // length == 0
   var length = %_ArgumentsLength();
   var array = new this(length);
   for (var i = 0; i < length; i++) {
@@ -104,21 +152,19 @@ function NAMEOf() {  // length == 0
   return array;
 }
 
-endmacro
-
-TYPED_ARRAYS(TYPED_ARRAY_HARMONY_ADDITIONS)
-
+%FunctionSetLength(TypedArrayCopyWithin, 2);
 
-macro EXTEND_TYPED_ARRAY(ARRAY_ID, NAME, ELEMENT_SIZE)
+macro EXTEND_TYPED_ARRAY(NAME)
   // Set up non-enumerable functions on the object.
   $installFunctions(GlobalNAME, DONT_ENUM | DONT_DELETE | READ_ONLY, [
-    "of", NAMEOf
+    "of", TypedArrayOf
   ]);
 
   // Set up non-enumerable functions on the prototype object.
   $installFunctions(GlobalNAME.prototype, DONT_ENUM, [
-    "every", NAMEEvery,
-    "forEach", NAMEForEach
+    "copyWithin", TypedArrayCopyWithin,
+    "every", TypedArrayEvery,
+    "forEach", TypedArrayForEach
   ]);
 endmacro