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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// 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 "base/logging.h"
#include "base/macros.h"
#include "build/build_config.h"
namespace base {
namespace win {
// Initializes COM in the constructor (STA or MTA), and uninitializes COM in the
// destructor.
//
// 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 ScopedCOMInitializer {
public:
// Enum value provided to initialize the thread as an MTA instead of STA.
enum SelectMTA { kMTA };
// Constructor for STA initialization.
ScopedCOMInitializer() {
Initialize(COINIT_APARTMENTTHREADED);
}
// Constructor for MTA initialization.
explicit ScopedCOMInitializer(SelectMTA mta) {
Initialize(COINIT_MULTITHREADED);
}
~ScopedCOMInitializer() {
#ifndef NDEBUG
// Using the windows API directly to avoid dependency on platform_thread.
DCHECK_EQ(GetCurrentThreadId(), thread_id_);
#endif
if (succeeded())
CoUninitialize();
}
bool succeeded() const { return SUCCEEDED(hr_); }
private:
void Initialize(COINIT init) {
#ifndef NDEBUG
thread_id_ = GetCurrentThreadId();
#endif
hr_ = CoInitializeEx(NULL, init);
#ifndef NDEBUG
if (hr_ == S_FALSE)
LOG(ERROR) << "Multiple CoInitialize() calls for thread " << thread_id_;
else
DCHECK_NE(RPC_E_CHANGED_MODE, hr_) << "Invalid COM thread model change";
#endif
}
HRESULT hr_;
#ifndef NDEBUG
// In debug builds we use this variable to catch a potential bug where a
// ScopedCOMInitializer instance is deleted on a different thread than it
// was initially created on. If that ever happens it can have bad
// consequences and the cause can be tricky to track down.
DWORD thread_id_;
#endif
DISALLOW_COPY_AND_ASSIGN(ScopedCOMInitializer);
};
} // namespace win
} // namespace base
#endif // BASE_WIN_SCOPED_COM_INITIALIZER_H_
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