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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_WIN_SCOPED_COM_INITIALIZER_H_
#define BASE_WIN_SCOPED_COM_INITIALIZER_H_
#include <objbase.h>
#include <wrl/client.h>
#include "base/base_export.h"
#include "base/threading/thread_checker.h"
#include "base/win/com_init_balancer.h"
#include "base/win/scoped_windows_thread_environment.h"
namespace base {
namespace win {
// Initializes COM in the constructor (STA or MTA), and uninitializes COM in the
// destructor.
//
// It is strongly encouraged to block premature uninitialization of the COM
// libraries in threads that execute third-party code, as a way to protect
// against unbalanced CoInitialize/CoUninitialize pairs.
//
// WARNING: This should only be used once per thread, ideally scoped to a
// similar lifetime as the thread itself. You should not be using this in
// random utility functions that make COM calls -- instead ensure these
// functions are running on a COM-supporting thread!
class BASE_EXPORT ScopedCOMInitializer : public ScopedWindowsThreadEnvironment {
public:
// Enum value provided to initialize the thread as an MTA instead of STA.
enum SelectMTA { kMTA };
// Enum values which enumerates uninitialization modes for the COM library.
enum class Uninitialization {
// Default value. Used in threads where no third-party code is executed.
kAllow,
// Blocks premature uninitialization of the COM libraries before going out
// of scope. Used in threads where third-party code is executed.
kBlockPremature,
};
// Constructors for STA initialization.
explicit ScopedCOMInitializer(
Uninitialization uninitialization = Uninitialization::kAllow);
// Constructors for MTA initialization.
explicit ScopedCOMInitializer(
SelectMTA mta,
Uninitialization uninitialization = Uninitialization::kAllow);
ScopedCOMInitializer(const ScopedCOMInitializer&) = delete;
ScopedCOMInitializer& operator=(const ScopedCOMInitializer&) = delete;
~ScopedCOMInitializer() override;
// ScopedWindowsThreadEnvironment:
bool Succeeded() const override;
// Returns the value returned by `CoInitializeEx` at initialization.
HRESULT hr() const { return hr_; }
// Used for testing. Returns the COM balancer's apartment thread ref count.
DWORD GetCOMBalancerReferenceCountForTesting() const;
private:
void Initialize(COINIT init, Uninitialization uninitialization);
HRESULT hr_ = S_OK;
Microsoft::WRL::ComPtr<internal::ComInitBalancer> com_balancer_;
THREAD_CHECKER(thread_checker_);
};
} // namespace win
} // namespace base
#endif // BASE_WIN_SCOPED_COM_INITIALIZER_H_
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