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// Copyright 2020 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_COM_INIT_BALANCER_H_
#define BASE_WIN_COM_INIT_BALANCER_H_
#include <objidl.h>
#include <winnt.h>
#include <wrl/implements.h>
#include <optional>
#include "base/base_export.h"
#include "base/threading/thread_checker.h"
#include "base/win/windows_types.h"
namespace base {
namespace win {
namespace internal {
// Implementation class of the IInitializeSpy Interface that prevents premature
// uninitialization of the COM library, often caused by unbalanced
// CoInitialize/CoUninitialize pairs. The use of this class is encouraged in
// COM-supporting threads that execute third-party code.
//
// Disable() must be called before uninitializing the COM library in order to
// revoke the registered spy and allow for the successful uninitialization of
// the COM library.
class BASE_EXPORT ComInitBalancer
: public Microsoft::WRL::RuntimeClass<
Microsoft::WRL::RuntimeClassFlags<Microsoft::WRL::ClassicCom>,
IInitializeSpy> {
public:
// Constructs a COM initialize balancer. |co_init| defines the apartment's
// concurrency model used by the balancer.
explicit ComInitBalancer(DWORD co_init);
ComInitBalancer(const ComInitBalancer&) = delete;
ComInitBalancer& operator=(const ComInitBalancer&) = delete;
~ComInitBalancer() override;
// Disables balancer by revoking the registered spy and consequently
// unblocking attempts to uninitialize the COM library.
void Disable();
DWORD GetReferenceCountForTesting() const;
private:
// IInitializeSpy:
IFACEMETHODIMP PreInitialize(DWORD apartment_type,
DWORD reference_count) override;
IFACEMETHODIMP PostInitialize(HRESULT result,
DWORD apartment_type,
DWORD new_reference_count) override;
IFACEMETHODIMP PreUninitialize(DWORD reference_count) override;
IFACEMETHODIMP PostUninitialize(DWORD new_reference_count) override;
const DWORD co_init_;
// The current apartment reference count set after the completion of the last
// call made to CoInitialize or CoUninitialize.
DWORD reference_count_ = 0;
std::optional<ULARGE_INTEGER> spy_cookie_;
THREAD_CHECKER(thread_checker_);
};
} // namespace internal
} // namespace win
} // namespace base
#endif // BASE_WIN_COM_INIT_BALANCER_H_
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