Add a helper for implementing Promise-valued properties.

Source/bindings/core/v8/ScriptPromiseProperty.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ScriptPromiseProperty_h
+#define ScriptPromiseProperty_h
+
+#include "bindings/core/v8/ScriptPromise.h"
+#include "bindings/core/v8/ScriptPromisePropertyBase.h"
+#include "bindings/core/v8/V8Binding.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/PassRefPtr.h"
+
+namespace WebCore {
+
+class ExecutionContext;
+
+// ScriptPromiseProperty is a helper for implementing a DOM method or
+// attribute whose value is a Promise, and the same Promise must be
+// returned each time.
+//
+// ScriptPromiseProperty does not keep Promises or worlds alive to
+// deliver Promise resolution/rejection to them; the Promise
+// resolution/rejections are delivered if the holder's wrapper is
+// alive. This is achieved by keeping a weak reference from
+// ScriptPromiseProperty to the holder's wrapper, and references in
+// hidden values between the wrapper, promise and resolver
+// (coincidentally the Resolver and Promise may be the same object,
+// but that is an implementation detail of v8.)
+//
+//                                             -----> Resolver
+//                                            /
+// ScriptPromiseProperty - - -> Holder Wrapper <------.
+//                                            \       |
+//                                             -----> Promise
+//
+// To avoid exposing the action of the garbage collector to script,
+// you should keep the wrapper alive as long as a promise may be
+// settled.
+//
+// ScriptPromiseProperty only supports the main world.
+// FIXME: Implement support for isolated worlds.
+template<typename HolderType, typename ResolvedType, typename RejectedType>
+class ScriptPromiseProperty : public ScriptPromisePropertyBase {
+    WTF_MAKE_NONCOPYABLE(ScriptPromiseProperty);
+public:
+    // Creates a ScriptPromiseProperty that will create Promises in
+    // the specified ExecutionContext for a property of 'holder'
+    // (typically ScriptPromiseProperty should be a member of the
+    // property holder).
+    //
+    // When implementing a ScriptPromiseProperty add the property name
+    // to ScriptPromiseProperties.h and pass
+    // ScriptPromiseProperty::Foo to create. The name must be unique
+    // per kind of holder.
+    template<typename PassHolderType>
+    static PassRefPtrWillBeRawPtr<ScriptPromiseProperty<HolderType, ResolvedType, RejectedType> > create(ExecutionContext*, PassHolderType, Name);
+
+    virtual ~ScriptPromiseProperty() { }
+
+    template<typename PassResolvedType>
+    void resolve(PassResolvedType);
+
+    template<typename PassRejectedType>
+    void reject(PassRejectedType);
+
+private:
+    template<typename PassHolderType>
+    ScriptPromiseProperty(ExecutionContext*, PassHolderType, Name);
+
+    virtual v8::Handle<v8::Object> holder(v8::Handle<v8::Object> creationContext, v8::Isolate*) OVERRIDE;
+    virtual v8::Handle<v8::Value> resolvedValue(v8::Handle<v8::Object> creationContext, v8::Isolate*) OVERRIDE;
+    virtual v8::Handle<v8::Value> rejectedValue(v8::Handle<v8::Object> creationContext, v8::Isolate*) OVERRIDE;
+
+    HolderType m_holder;
+    ResolvedType m_resolved;
+    RejectedType m_rejected;
+};
+
+template<typename HolderType, typename ResolvedType, typename RejectedType>
+template<typename PassHolderType>
+PassRefPtrWillBeRawPtr<ScriptPromiseProperty<HolderType, ResolvedType, RejectedType> > ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>::create(ExecutionContext* executionContext, PassHolderType holder, Name name)
+{
+    return adoptRef(new ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>(executionContext, holder, name));
+}
+
+template<typename HolderType, typename ResolvedType, typename RejectedType>
+template<typename PassHolderType>
+ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>::ScriptPromiseProperty(ExecutionContext* executionContext, PassHolderType holder, Name name)
+    : ScriptPromisePropertyBase(executionContext, name)
+    , m_holder(holder)
+{
+}
+
+template<typename HolderType, typename ResolvedType, typename RejectedType>
+template<typename PassResolvedType>
+void ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>::resolve(PassResolvedType value)
+{
+    if (state() != Pending) {
+        ASSERT_NOT_REACHED();
+        return;
+    }
+    if (!executionContext())
+        return;
+    m_resolved = value;
+    resolveOrReject(Resolved);
+}
+
+template<typename HolderType, typename ResolvedType, typename RejectedType>
+template<typename PassRejectedType>
+void ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>::reject(PassRejectedType value)
+{
+    if (state() != Pending) {
+        ASSERT_NOT_REACHED();
+        return;
+    }
+    if (!executionContext())
+        return;
+    m_rejected = value;
+    resolveOrReject(Rejected);
+}
+
+template<typename HolderType, typename ResolvedType, typename RejectedType>
+v8::Handle<v8::Object> ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>::holder(v8::Handle<v8::Object> creationContext, v8::Isolate* isolate)
+{
+    v8::Handle<v8::Value> value = V8ValueTraits<HolderType>::toV8Value(m_holder, creationContext, isolate);
+    return value.As<v8::Object>();
+}
+
+template<typename HolderType, typename ResolvedType, typename RejectedType>
+v8::Handle<v8::Value> ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>::resolvedValue(v8::Handle<v8::Object> creationContext, v8::Isolate* isolate)
+{
+    ASSERT(state() == Resolved);
+    return V8ValueTraits<ResolvedType>::toV8Value(m_resolved, creationContext, isolate);
+}
+
+template<typename HolderType, typename ResolvedType, typename RejectedType>
+v8::Handle<v8::Value> ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>::rejectedValue(v8::Handle<v8::Object> creationContext, v8::Isolate* isolate)
+{
+    ASSERT(state() == Rejected);
+    return V8ValueTraits<RejectedType>::toV8Value(m_rejected, creationContext, isolate);
+}
+
+} // namespace WebCore
+
+#endif // ScriptPromiseProperty_h