TypedArray(length) constructor

src/typedarray.js

Index: src/typedarray.js
diff --git a/src/typedarray.js b/src/typedarray.js
index 7549652e1fa2ef92c68bc8a02127cafef99c9a27..4e50f7f3dffdb46eadecca0b3faf3bd7587b9c1c 100644
--- a/src/typedarray.js
+++ b/src/typedarray.js
@@ -85,42 +85,54 @@ function ArrayBufferSlice(start, end) {
 // --------------- Typed Arrays ---------------------
 
 function CreateTypedArrayConstructor(name, elementSize, arrayId, constructor) {
-  return function (buffer, byteOffset, length) {
-    if (%_IsConstructCall()) {
-      if (!IS_ARRAYBUFFER(buffer)) {
-        throw MakeTypeError("Type error!");
-      }
-      var offset = IS_UNDEFINED(byteOffset)
-        ? 0 : offset = TO_POSITIVE_INTEGER(byteOffset);
+  function ConstructByArrayBuffer(obj, buffer, byteOffset, length) {
+    var offset = IS_UNDEFINED(byteOffset)
+      ? 0 : offset = TO_POSITIVE_INTEGER(byteOffset);
+
+    if (offset % elementSize !== 0) {
+      throw MakeRangeError("invalid_typed_array_alignment",
+          "start offset", name, elementSize);
+    }
+    var bufferByteLength = %ArrayBufferGetByteLength(buffer);
+    if (offset >= bufferByteLength) {
+      throw MakeRangeError("invalid_typed_array_offset");
+    }
 
-      if (offset % elementSize !== 0) {
+    var newByteLength;
+    var newLength;
+    if (IS_UNDEFINED(length)) {
+      if (bufferByteLength % elementSize !== 0) {
         throw MakeRangeError("invalid_typed_array_alignment",
-            "start offset", name, elementSize);
-      }
-      var bufferByteLength = %ArrayBufferGetByteLength(buffer);
-      if (offset >= bufferByteLength) {
-        throw MakeRangeError("invalid_typed_array_offset");
+          "byte length", name, elementSize);
       }
+      newByteLength = bufferByteLength - offset;
+      newLength = newByteLength / elementSize;
+    } else {
+      var newLength = TO_POSITIVE_INTEGER(length);
+      newByteLength = newLength * elementSize;
+    }
+    if (newByteLength > bufferByteLength) {
+      throw MakeRangeError("invalid_typed_array_length");
+    }
+    %TypedArrayInitialize(obj, arrayId, buffer, offset, newByteLength);
+  }
+
+  function ConstructByLength(obj, length) {
+    var l = IS_UNDEFINED(length) ? 0 : TO_POSITIVE_INTEGER(length);
+    var byteLength = l * elementSize;
+    var buffer = new $ArrayBuffer(byteLength);
+    %TypedArrayInitialize(obj, arrayId, buffer, 0, byteLength);
+  }
 
-      var newByteLength;
-      var newLength;
-      if (IS_UNDEFINED(length)) {
-        if (bufferByteLength % elementSize !== 0) {
-          throw MakeRangeError("invalid_typed_array_alignment",
-            "byte length", name, elementSize);
-        }
-        newByteLength = bufferByteLength - offset;
-        newLength = newByteLength / elementSize;
+  return function (arg1, arg2, arg3) {
+    if (%_IsConstructCall()) {

[rossberg, 2013/04/29 15:17:15]

Nit: if you negate this condition, you can avoid the extra if-nesting.

+      if (IS_ARRAYBUFFER(arg1)) {
+        ConstructByArrayBuffer(this, arg1, arg2, arg3);
       } else {
-        var newLength = TO_POSITIVE_INTEGER(length);
-        newByteLength = newLength * elementSize;
-      }
-      if (newByteLength > bufferByteLength) {
-        throw MakeRangeError("invalid_typed_array_length");
+        ConstructByLength(this, arg1);
       }
-      %TypedArrayInitialize(this, arrayId, buffer, offset, newByteLength);
     } else {
-      return new constructor(buffer, byteOffset, length);
+      return new constructor(arg1, arg2, arg3);
     }
   }
 }
@@ -164,9 +176,10 @@ function SetUpArrayBuffer() {
 SetUpArrayBuffer();
 
 function SetupTypedArray(arrayId, name, constructor, elementSize) {
-  var f = CreateTypedArrayConstructor(name, elementSize,
-                                      arrayId, constructor);
-  %SetCode(constructor, f);
+  %CheckIsBootstrapping();
+  var fun = CreateTypedArrayConstructor(name, elementSize,
+                                        arrayId, constructor);
+  %SetCode(constructor, fun);
   %FunctionSetPrototype(constructor, new $Object());
 
   %SetProperty(constructor.prototype,