Implement BroadcastChannel

third_party/WebKit/Source/modules/broadcastchannel/BroadcastChannel.cpp

+// Copyright 2016 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.
+
+#include "modules/broadcastchannel/BroadcastChannel.h"
+
+#include "bindings/core/v8/SerializedScriptValue.h"
+#include "core/dom/ExceptionCode.h"
+#include "core/events/EventQueue.h"
+#include "core/events/MessageEvent.h"
+
+namespace blink {
+
+// static
+BroadcastChannel* BroadcastChannel::create(ExecutionContext* executionContext, const String& name, ExceptionState& exceptionState)
+{
+    if (executionContext->getSecurityOrigin()->isUnique()) {
+        // TODO(mek): Decide what to do here depending on https://github.com/whatwg/html/issues/1319
+        exceptionState.throwDOMException(NotSupportedError, "Can't create BroadcastChannel in an opaque origin");
+        return nullptr;
+    }
+    return new BroadcastChannel(executionContext, name);
+}
+
+BroadcastChannel::~BroadcastChannel()
+{
+}
+
+void BroadcastChannel::postMessage(const ScriptValue& message, ExceptionState& exceptionState)
+{
+    if (!m_connection) {
+        exceptionState.throwDOMException(InvalidStateError, "Channel is closed");
+        return;
+    }
+    RefPtr<SerializedScriptValue> value = SerializedScriptValue::serialize(message.isolate(), message.v8Value(), nullptr, nullptr, exceptionState);
+    if (exceptionState.hadException())
+        return;
+
+    String data = value->toWireString();
+    m_connection->broadcast(this, data);
+}
+
+void BroadcastChannel::close()
+{
+    if (m_connection)
+        m_connection->unregisterClient(this);
+    m_connection = nullptr;
+}
+
+void BroadcastChannel::onMessage(const String& message)
+{
+    // Queue a task to dispatch the event.
+    RefPtr<SerializedScriptValue> value = SerializedScriptValue::create(message);
+    MessageEvent* event = MessageEvent::create(nullptr, value.release(), getExecutionContext()->getSecurityOrigin()->toString());
+    event->setTarget(this);
+    bool success = getExecutionContext()->getEventQueue()->enqueueEvent(event);
+    DCHECK(success);
+    ALLOW_UNUSED_LOCAL(success);

[haraken, 2016/06/06 02:05:47]

Nit: Do we need this?

[Marijn Kruisselbrink, 2016/06/06 20:05:29]

Not sure. Assertions.h seems to suggest so though by suggesting that
DCHECK+ALLOW_UNUSED_LOCAL is the correct replacement for ASSERT_UNUSED.

+}
+
+void BroadcastChannel::onError()
+{
+    m_connection = nullptr;

[haraken, 2016/06/06 02:05:47]

Do you really want to clear m_connection before calling close()?

[Marijn Kruisselbrink, 2016/06/06 20:05:29]

Good question. That pretty much turns close() into a no-op in this case. I do
want to avoid the call to unregisterClient though, as that just makes the code
in the BCConnection implementation a bit simpler (hence the unclear "After
onError is called a client should not try to do anything with the connection
anymore" comment, which I now made a bit more explicit about this specific
case).

+    close();
+}
+
+const AtomicString& BroadcastChannel::interfaceName() const
+{
+    return EventTargetNames::BroadcastChannel;
+}
+
+bool BroadcastChannel::hasPendingActivity() const
+{
+    return m_connection && hasEventListeners(EventTypeNames::message);
+}
+
+DEFINE_TRACE(BroadcastChannel)
+{
+    ContextLifecycleObserver::trace(visitor);
+    EventTargetWithInlineData::trace(visitor);
+    visitor->trace(m_connection);
+}
+
+BroadcastChannel::BroadcastChannel(ExecutionContext* executionContext, const String& name)
+    : ActiveScriptWrappable(this)
+    , ContextLifecycleObserver(executionContext)

[haraken, 2016/06/06 02:05:47]

The fact that you're observing ContextLifecycleObserver means that you want to
observe when the ExecutionContext stops (and take some action). If not, you
should instead just add WeakMember<ExecutionContext> or Member<ExecutionContext>
to BroadcastChannel.

I'm guessing that you want to close the connection when the ExecutionContext
stops (i.e., Document::detach() is called). If that is the case, you should
override ContextLifecycleObserver::contextDestroyed() and call close().

[haraken, 2016/06/07 00:53:26]

Any idea on this?

[Marijn Kruisselbrink, 2016/06/07 01:18:39]

Sorry about missing this one. Yes, contextDestroyed should call close() (just
curious, do you know if there is any particular reason why MessagePort overrides
ActiveDOMObject::stop for presumably the same behavior?)

[haraken, 2016/06/07 01:29:55]

Don't know. But I think MessagePort should inherit from
ContextLifecycleObserver, not ActiveDOMObject. ActiveDOMObject makes sense only
when it defines behavior for suspend and resume.

+    , m_origin(executionContext->getSecurityOrigin())
+    , m_name(name)
+    , m_connection(BroadcastChannelConnection::getForChannel(m_origin, m_name))
+{
+    m_connection->registerClient(this);
+}
+
+} // namespace blink