зеркало из https://github.com/mozilla/gecko-dev.git
148 строки
3.8 KiB
C++
148 строки
3.8 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_mscom_EnsureMTA_h
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#define mozilla_mscom_EnsureMTA_h
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#include "MainThreadUtils.h"
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#include "mozilla/Attributes.h"
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#include "mozilla/DebugOnly.h"
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#include "mozilla/Unused.h"
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#include "mozilla/mscom/COMApartmentRegion.h"
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#include "mozilla/mscom/Utils.h"
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#include "nsCOMPtr.h"
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#include "nsIThread.h"
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#include "nsThreadUtils.h"
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#include "nsWindowsHelpers.h"
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#include <windows.h>
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namespace mozilla {
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namespace mscom {
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namespace detail {
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// Forward declarations
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template <typename T>
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struct MTADelete;
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template <typename T>
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struct MTARelease;
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template <typename T>
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struct MTAReleaseInChildProcess;
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struct PreservedStreamDeleter;
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}
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// This class is OK to use as a temporary on the stack.
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class MOZ_STACK_CLASS EnsureMTA final
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{
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public:
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/**
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* This constructor just ensures that the MTA thread is up and running.
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*/
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EnsureMTA()
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{
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MOZ_ASSERT(NS_IsMainThread());
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nsCOMPtr<nsIThread> thread = GetMTAThread();
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MOZ_ASSERT(thread);
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Unused << thread;
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}
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template <typename FuncT>
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explicit EnsureMTA(const FuncT& aClosure)
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{
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if (IsCurrentThreadMTA()) {
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// We're already on the MTA, we can run aClosure directly
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aClosure();
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return;
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}
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MOZ_ASSERT(NS_IsMainThread());
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// In this case we need to run aClosure on a background thread in the MTA
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nsCOMPtr<nsIThread> thread = GetMTAThread();
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MOZ_ASSERT(thread);
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if (!thread) {
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return;
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}
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// Note that we might reenter the EnsureMTA constructor while we wait on
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// this event due to APC dispatch, therefore we need a unique event object
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// for each entry. If perf becomes an issue then we will want to maintain
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// an array of events where the Nth event is unique to the Nth reentry.
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nsAutoHandle event(::CreateEventW(nullptr, FALSE, FALSE, nullptr));
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if (!event) {
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return;
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}
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HANDLE eventHandle = event.get();
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auto eventSetter = [&aClosure, eventHandle]() -> void {
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aClosure();
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::SetEvent(eventHandle);
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};
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nsresult rv =
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thread->Dispatch(NS_NewRunnableFunction("EnsureMTA", eventSetter), NS_DISPATCH_NORMAL);
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MOZ_ASSERT(NS_SUCCEEDED(rv));
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if (NS_FAILED(rv)) {
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return;
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}
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DWORD waitResult;
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while ((waitResult = ::WaitForSingleObjectEx(event, INFINITE, TRUE)) ==
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WAIT_IO_COMPLETION) {
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}
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MOZ_ASSERT(waitResult == WAIT_OBJECT_0);
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}
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private:
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static nsCOMPtr<nsIThread> GetMTAThread();
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// The following function is private in order to force any consumers to be
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// declared as friends of EnsureMTA. The intention is to prevent
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// AsyncOperation from becoming some kind of free-for-all mechanism for
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// asynchronously executing work on a background thread.
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template <typename FuncT>
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static void AsyncOperation(const FuncT& aClosure)
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{
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if (IsCurrentThreadMTA()) {
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aClosure();
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return;
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}
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nsCOMPtr<nsIThread> thread(GetMTAThread());
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MOZ_ASSERT(thread);
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if (!thread) {
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return;
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}
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DebugOnly<nsresult> rv = thread->Dispatch(
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NS_NewRunnableFunction("mscom::EnsureMTA::AsyncOperation",
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aClosure), NS_DISPATCH_NORMAL);
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MOZ_ASSERT(NS_SUCCEEDED(rv));
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}
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template <typename T>
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friend struct mozilla::mscom::detail::MTADelete;
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template <typename T>
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friend struct mozilla::mscom::detail::MTARelease;
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template <typename T>
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friend struct mozilla::mscom::detail::MTAReleaseInChildProcess;
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friend struct mozilla::mscom::detail::PreservedStreamDeleter;
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};
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} // namespace mscom
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} // namespace mozilla
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#endif // mozilla_mscom_EnsureMTA_h
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