Web MIDI: implement MIDIAccessPromise

Source/modules/webmidi/MIDIAccessPromise.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
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+ *
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+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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+ * 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 "modules/webmidi/MIDIAccessPromise.h"
+
+#include "core/dom/DOMError.h"
+#include "modules/webmidi/MIDIAccess.h"
+#include "modules/webmidi/MIDIErrorCallback.h"
+#include "modules/webmidi/MIDISuccessCallback.h"
+
+namespace WebCore {
+
+PassRefPtr<MIDIAccessPromise> MIDIAccessPromise::create(ScriptExecutionContext* context, const Dictionary& options)
+{
+    RefPtr<MIDIAccessPromise> midiAccessPromise(adoptRef(new MIDIAccessPromise(context, options)));
+    midiAccessPromise->suspendIfNeeded();
+    return midiAccessPromise.release();
+}
+
+MIDIAccessPromise::MIDIAccessPromise(ScriptExecutionContext* context, const Dictionary& options)
+    : ActiveDOMObject(context)
+    , m_state(Pending)
+    , m_options(adoptPtr(new MIDIOptions(options)))
+    , m_access(MIDIAccess::create(context, this))
+{
+    ScriptWrappable::init(this);
+    setPendingActivity(this);
+}
+
+MIDIAccessPromise::~MIDIAccessPromise()
+{
+    stop();
+}
+
+void MIDIAccessPromise::fulfill()
+{
+    if (m_state == Pending) {
+        if (m_successCallback) {
+            m_state = Invoked;
+            m_successCallback->handleEvent(m_access.release().leakRef(), m_options->sysexEnabled);
+            m_options.clear();
+        } else {
+            m_state = Accepted;
+        }
+        unsetPendingActivity(this);
+    }
+    m_successCallback.clear();
+    m_errorCallback.clear();

[Chris Rogers, 2013/06/07 19:19:46]

It seems that the m_successCallback cannot be cleared right here if we have just
entered the Accepted state (line 71).  Since when then() is called later on, it
won't be able to call handleEvent to call the success callback.

I think it's safer to not clear either of these callbacks, or if they are
cleared to clear each one separately after the callback has actually been made

[Takashi Toyoshima, 2013/06/10 13:56:04]

When then() is called later on, |successCallback| of then()'s argument should be
invoked.
fulfill() and reject() are only place which invoke m_successCallback or
m_errorCallback.
When then() invokes a callback, it uses one of arguments.

+}
+
+void MIDIAccessPromise::reject(DOMError* error)
+{
+    if (m_state == Pending) {
+        if (m_errorCallback) {
+            m_state = Invoked;
+            m_errorCallback->handleEvent(error);
+        } else {
+            m_state = Rejected;
+            m_error = adoptRef(error);
+        }
+        unsetPendingActivity(this);
+    }
+    m_successCallback.clear();
+    m_errorCallback.clear();
+}
+
+void MIDIAccessPromise::then(PassRefPtr<MIDISuccessCallback> successCallback, PassRefPtr<MIDIErrorCallback> errorCallback)
+{
+    switch (m_state) {
+    case Accepted:
+        successCallback->handleEvent(m_access.release().leakRef(), m_options->sysexEnabled);
+        m_options.clear();
+        m_state = Invoked;
+        break;
+    case Rejected:
+        errorCallback->handleEvent(m_error.release().leakRef());
+        m_state = Invoked;
+        break;
+    case Pending:
+        m_successCallback = successCallback;
+        m_errorCallback = errorCallback;
+        break;
+    case Invoked:
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
+} // namespace WebCore