IDL: Add PropertyBag class

Source/bindings/core/v8/PropertyBag.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 PropertyBag_h
+#define PropertyBag_h
+
+#include "bindings/core/v8/V8Binding.h"
+#include "wtf/Noncopyable.h"
+#include <v8.h>
+
+namespace blink {
+
+template <typename T> struct PropertyBagTraits;
+
+// PropertyBag is used by IDL dictionary implementations to retrieve native
+// values from a V8 object. It is similar to Dictionary(Helper), but its get()
+// method returns false when the V8 object doesn't have the given key.
+// FIXME: Eliminate duplication between Dictionary(Helper) and PropertyBag.
+// When we have enough IDL dictionary support, we should be able to remove
+// Dictionary(Helper).
+class PropertyBag {
+    WTF_MAKE_NONCOPYABLE(PropertyBag);
+public:
+    PropertyBag(v8::Isolate* isolate, const v8::Handle<v8::Object>& object)
+        : m_isolate(isolate)
+        , m_object(object)
+    {
+        ASSERT(!m_object.IsEmpty());
+    }
+
+    template <typename T>
+    bool get(const String& key, T& value)
+    {
+        v8::Handle<v8::String> v8Key = v8String(m_isolate, key);
+        v8::Local<v8::Value> v8Value = m_object->Get(v8Key);
+        if (v8Value.IsEmpty() || isUndefinedOrNull(v8Value)) {

[haraken, 2014/08/29 05:44:05]

Just to confirm: I understand you want to return false when v8Value is
undefined, but you also want to return false when v8Value is null, right?

+            return false;
+        }
+        return getInternal(v8Value, value);
+    }
+
+private:
+    bool getInternal(v8::Handle<v8::Value>& v8Value, String& value);

[haraken, 2014/08/29 05:44:04]

Drop |v8Value| and |value|.

+    bool getInternal(v8::Handle<v8::Value>& v8Value, int& value);
+    bool getInternal(v8::Handle<v8::Value>& v8Value, bool& value);
+    bool getInternal(v8::Handle<v8::Value>& v8Value, double& value);
+
+    template <template <typename> class PointerType, typename T>
+    bool getInternal(v8::Handle<v8::Value>& v8Value, PointerType<T>& value)
+    {
+        value = PropertyBagTraits<T>::type::toNativeWithTypeCheck(m_isolate, v8Value);
+        return value;
+    }
+
+    template <typename T>
+    bool getInternal(v8::Handle<v8::Value>& v8Value, Vector<T>& value)
+    {
+        if (!v8Value->IsArray())
+            return false;
+        // FIXME: Check types of each value
+        value = toNativeArray<T>(v8Value, 0, m_isolate);
+        return true;
+    }
+
+    v8::Isolate* m_isolate;
+    v8::Handle<v8::Object> m_object;
+};
+
+} // namespace blink
+
+#endif // PropertyBag_h