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-rw-r--r--ipc/mscom/EnsureMTA.h87
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diff --git a/ipc/mscom/EnsureMTA.h b/ipc/mscom/EnsureMTA.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_mscom_EnsureMTA_h
+#define mozilla_mscom_EnsureMTA_h
+
+#include "MainThreadUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Function.h"
+#include "mozilla/mscom/COMApartmentRegion.h"
+#include "mozilla/mscom/Utils.h"
+#include "nsCOMPtr.h"
+#include "nsIThread.h"
+#include "nsThreadUtils.h"
+
+#include <windows.h>
+
+namespace mozilla {
+namespace mscom {
+
+// This class is OK to use as a temporary on the stack.
+class MOZ_STACK_CLASS EnsureMTA
+{
+public:
+ /**
+ * This constructor just ensures that the MTA thread is up and running.
+ */
+ EnsureMTA()
+ {
+ MOZ_ASSERT(NS_IsMainThread());
+ nsCOMPtr<nsIThread> thread = GetMTAThread();
+ MOZ_ASSERT(thread);
+ }
+
+ template <typename FuncT>
+ EnsureMTA(const FuncT& aClosure)
+ {
+ MOZ_ASSERT(NS_IsMainThread());
+ if (IsCurrentThreadMTA()) {
+ // We're already on the MTA, we can run aClosure directly
+ aClosure();
+ return;
+ }
+
+ // In this case we need to run aClosure on a background thread in the MTA
+ nsCOMPtr<nsIThread> thread = GetMTAThread();
+ MOZ_ASSERT(thread);
+
+ HANDLE event = ::CreateEventW(nullptr, FALSE, FALSE, nullptr);
+ if (!event) {
+ return;
+ }
+
+ auto eventSetter = [&]() -> void {
+ aClosure();
+ ::SetEvent(event);
+ };
+
+ nsresult rv =
+ thread->Dispatch(NS_NewRunnableFunction(eventSetter), NS_DISPATCH_NORMAL);
+ MOZ_ASSERT(NS_SUCCEEDED(rv));
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ ::CloseHandle(event);
+ return;
+ }
+
+ DWORD waitResult;
+ while ((waitResult = ::WaitForSingleObjectEx(event, INFINITE, TRUE)) ==
+ WAIT_IO_COMPLETION) {
+ }
+ MOZ_ASSERT(waitResult == WAIT_OBJECT_0);
+ ::CloseHandle(event);
+ }
+
+private:
+ static nsCOMPtr<nsIThread> GetMTAThread();
+};
+
+} // namespace mscom
+} // namespace mozilla
+
+#endif // mozilla_mscom_EnsureMTA_h
+