Introduce Promises.

Source/bindings/v8/custom/V8PromiseCustom.cpp

+/*
+ * Copyright (C) 2013 Google Inc. 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.
+ */
+
+#include "config.h"
+#include "bindings/v8/custom/V8PromiseCustom.h"
+
+#include "V8Promise.h"
+#include "V8PromiseResolver.h"
+#include "bindings/v8/V8Binding.h"
+#include "bindings/v8/V8ScriptRunner.h"
+#include "bindings/v8/WrapperTypeInfo.h"
+#include <v8.h>
+
+namespace WebCore {
+
+void V8Promise::constructorCustom(const v8::FunctionCallbackInfo<v8::Value>& args)
+{
+    args.GetReturnValue().Set(v8::Local<v8::Value>());

[abarth-chromium, 2013/06/21 05:38:46]

There isn't a SetReturnValue function?

[yhirano, 2013/06/21 09:36:53]

Thanks, done.

+    v8::Isolate* isolate = args.GetIsolate();
+    if (args.Length() != 1 || args[0].IsEmpty() || !args[0]->IsFunction()) {

[haraken, 2013/06/21 05:47:58]

This should be 'args.Length() < 1'.

[yhirano, 2013/06/21 09:36:53]

Done.

+        throwTypeError("Promise constructor takes exact one function argument", isolate);
+        return;
+    }
+    v8::Handle<v8::Function> init = args[0].As<v8::Function>();
+    v8::Local<v8::ObjectTemplate> associatedTemplate = v8::ObjectTemplate::New();

[abarth-chromium, 2013/06/21 05:38:46]

Normally we create the object template in V8PerIsolateData.  Can we store the
template there and just clone it for each call to the constructor?  That's much
more efficient because it helps V8 understand that the object's structure is
shared among all its instances.

[yhirano, 2013/06/21 09:36:53]

We can attach FunctionTemplate data to V8PerIsolateData, but cannot attach
ObjectTemplate.

+    associatedTemplate->SetInternalFieldCount(V8PromiseCustom::AssociatedInternalFieldCount);
+    v8::Local<v8::Object> associated = associatedTemplate->NewInstance();
+    v8::Local<v8::Object> promise = V8DOMWrapper::createWrapper(args.Holder(), &V8Promise::info, 0, isolate);
+    v8::Local<v8::Object> promiseResolver = V8DOMWrapper::createWrapper(args.Holder(), &V8PromiseResolver::info, 0, isolate);

[haraken, 2013/06/21 05:47:58]

Don't you need to store a C++ object pointer to the wrapper? (I don't fully
understand how Promise works.)

[abarth-chromium, 2013/06/21 05:58:53]

The "associated" object isn't a wrapper.  It's just a V8 object with a number of
internal fields.  I how that won't confuse other code in the bindings...  We
might need to reserve the first two lots for zeros.

[yhirano, 2013/06/21 09:36:53]

No, instead, we set a JavaScript object as an internal field to it.

+
+    associated->SetInternalField(V8PromiseCustom::AssociatedStatusIndex, v8::NumberObject::New(V8PromiseCustom::Pending));

[abarth-chromium, 2013/06/21 05:38:46]

These plain numbers we can keep on the CPP side.  It's only the references to
other V8 objects that need to be in the V8 side, strictly speaking.  However, I
can see the appeal of keeping all the data on the V8 side, especially if that
means there's no CPP object at all!

+    associated->SetInternalField(V8PromiseCustom::AssociatedResultIndex, v8::Undefined());
+    associated->SetInternalField(V8PromiseCustom::AssociatedFulfillCallbackIndex, v8::Array::New());
+    associated->SetInternalField(V8PromiseCustom::AssociatedRejectCallbackIndex, v8::Array::New());
+
+    promise->SetInternalField(v8DOMWrapperObjectIndex, associated);
+    promiseResolver->SetInternalField(v8DOMWrapperObjectIndex, associated);

[abarth-chromium, 2013/06/21 05:38:46]

These two object share the same associated storage object?  /me doesn't fully
understand how promises work...

Is there a more descriptive name we can use than "associated" ?  I guess this is
the state for the promise?

[yhirano, 2013/06/21 09:36:53]

Hmm...
There is "state" property in the spec (I called it as "status" in PS1, but it
was wrong).
How about "internal"?

+
+    v8::Handle<v8::Value> argv[] = {
+        promiseResolver,
+    };
+    v8::TryCatch trycatch;
+    if (init->Call(promise, sizeof(argv) / sizeof(argv[0]), argv).IsEmpty()) {

[abarth-chromium, 2013/06/21 05:38:46]

WTF_ARRAY_LENGTH(argv)

[haraken, 2013/06/21 05:47:58]

You can use V8ScriptRunner::callFunction().

[abarth-chromium, 2013/06/21 05:58:53]

Ah, sorry I missed that!

[yhirano, 2013/06/21 09:36:53]

Done.

+        // FIXME: An exception is thrown. Reject the promise.
+    }
+    args.GetReturnValue().Set(promise);
+    return;
+}
+
+} // namespace WebCore