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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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
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