First steps towards implementing ArrayBuffer &co in V8

src/typedarray.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"use strict";
+
+var $ArrayBuffer = global.__ArrayBuffer;
+
+function ArrayBufferConstructor(byteLength) { // length = 1
+  if (%_IsConstructCall()) {
+    var l = TO_POSITIVE_INTEGER(byteLength);
+    %ArrayBufferInitialize(this, l);
+  } else {
+    return new $ArrayBuffer(byteLength);
+  }
+}
+
+function ArrayBufferGetByteLength() {
+  if (!IS_ARRAYBUFFER(this)) {
+    throw MakeTypeError('incompatible_method_receiver',
+                        ['ArrayBuffer.prototype.byteLength', this]);
+  }
+  return %ArrayBufferGetByteLength(this);
+}
+
+// ES6 Draft 15.13.5.5.3
+function ArrayBufferSlice(start, end) {
+  if (!IS_ARRAYBUFFER(this)) {
+    throw MakeTypeError('incompatible_method_receiver',
+                        ['ArrayBuffer.prototype.slice', this]);
+  }
+
+  var relativeStart = TO_INTEGER(start);
+  var first;
+  if (relativeStart < 0) {
+    first = MathMax(this.byteLength + relativeStart, 0);
+  } else {
+    first = MathMin(relativeStart, this.byteLength);
+  }
+  var relativeEnd = IS_UNDEFINED(end) ? this.byteLength : end;

[rossberg, 2013/03/27 17:33:14]

Don't you have to convert 'end' to integer?

[Dmitry Lomov (no reviews), 2013/03/27 18:45:00]

Good catch, done and added a test

+  var fin;
+  if (relativeEnd < 0) {
+    fin = MathMax(this.byteLength + relativeEnd, 0);
+  } else {
+    fin = MathMin(relativeEnd, this.byteLength);
+  }
+
+  var newLen = fin - first;
+  // TODO(dslomov): implement inheritance
+  var result = new $ArrayBuffer(newLen);
+
+  %ArrayBufferSliceImpl(this, result, first);
+  return result;
+}
+
+
+
+// -------------------------------------------------------------------
+
+(function () {
+  %CheckIsBootstrapping();
+
+  // Set up the Uint16Array constructor function.
+  %SetCode($ArrayBuffer, ArrayBufferConstructor);
+
+  // Set up the constructor property on the ArrayBuffer prototype object.
+  %SetProperty($ArrayBuffer.prototype, "constructor", $ArrayBuffer, DONT_ENUM);
+
+  InstallGetter($ArrayBuffer.prototype, "byteLength", ArrayBufferGetByteLength);
+
+  InstallFunctions($ArrayBuffer.prototype, DONT_ENUM, $Array(
+      "slice", ArrayBufferSlice
+  ));
+
+})();