1// Copyright (c) 2012 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#ifndef BASE_WIN_SCOPED_COM_INITIALIZER_H_ 6#define BASE_WIN_SCOPED_COM_INITIALIZER_H_ 7 8#include <objbase.h> 9 10#include "base/basictypes.h" 11#include "base/logging.h" 12#include "build/build_config.h" 13 14namespace base { 15namespace win { 16 17// Initializes COM in the constructor (STA or MTA), and uninitializes COM in the 18// destructor. 19// 20// WARNING: This should only be used once per thread, ideally scoped to a 21// similar lifetime as the thread itself. You should not be using this in 22// random utility functions that make COM calls -- instead ensure these 23// functions are running on a COM-supporting thread! 24class ScopedCOMInitializer { 25 public: 26 // Enum value provided to initialize the thread as an MTA instead of STA. 27 enum SelectMTA { kMTA }; 28 29 // Constructor for STA initialization. 30 ScopedCOMInitializer() { 31 Initialize(COINIT_APARTMENTTHREADED); 32 } 33 34 // Constructor for MTA initialization. 35 explicit ScopedCOMInitializer(SelectMTA mta) { 36 Initialize(COINIT_MULTITHREADED); 37 } 38 39 ~ScopedCOMInitializer() { 40#ifndef NDEBUG 41 // Using the windows API directly to avoid dependency on platform_thread. 42 DCHECK_EQ(GetCurrentThreadId(), thread_id_); 43#endif 44 if (succeeded()) 45 CoUninitialize(); 46 } 47 48 bool succeeded() const { return SUCCEEDED(hr_); } 49 50 private: 51 void Initialize(COINIT init) { 52#ifndef NDEBUG 53 thread_id_ = GetCurrentThreadId(); 54#endif 55 hr_ = CoInitializeEx(NULL, init); 56#ifndef NDEBUG 57 if (hr_ == S_FALSE) 58 LOG(ERROR) << "Multiple CoInitialize() calls for thread " << thread_id_; 59 else 60 DCHECK_NE(RPC_E_CHANGED_MODE, hr_) << "Invalid COM thread model change"; 61#endif 62 } 63 64 HRESULT hr_; 65#ifndef NDEBUG 66 // In debug builds we use this variable to catch a potential bug where a 67 // ScopedCOMInitializer instance is deleted on a different thread than it 68 // was initially created on. If that ever happens it can have bad 69 // consequences and the cause can be tricky to track down. 70 DWORD thread_id_; 71#endif 72 73 DISALLOW_COPY_AND_ASSIGN(ScopedCOMInitializer); 74}; 75 76} // namespace win 77} // namespace base 78 79#endif // BASE_WIN_SCOPED_COM_INITIALIZER_H_ 80