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      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 
     14 namespace base {
     15 namespace win {
     16 
     17 // Initializes COM in the constructor (STA or MTA), and uninitializes COM in the
     18 // destructor.
     19 class ScopedCOMInitializer {
     20  public:
     21   // Enum value provided to initialize the thread as an MTA instead of STA.
     22   enum SelectMTA { kMTA };
     23 
     24   // Constructor for STA initialization.
     25   ScopedCOMInitializer() {
     26     Initialize(COINIT_APARTMENTTHREADED);
     27   }
     28 
     29   // Constructor for MTA initialization.
     30   explicit ScopedCOMInitializer(SelectMTA mta) {
     31     Initialize(COINIT_MULTITHREADED);
     32   }
     33 
     34   ~ScopedCOMInitializer() {
     35 #ifndef NDEBUG
     36     // Using the windows API directly to avoid dependency on platform_thread.
     37     DCHECK_EQ(GetCurrentThreadId(), thread_id_);
     38 #endif
     39     if (succeeded())
     40       CoUninitialize();
     41   }
     42 
     43   bool succeeded() const { return SUCCEEDED(hr_); }
     44 
     45  private:
     46   void Initialize(COINIT init) {
     47 #ifndef NDEBUG
     48     thread_id_ = GetCurrentThreadId();
     49 #endif
     50     hr_ = CoInitializeEx(NULL, init);
     51 #ifndef NDEBUG
     52     if (hr_ == S_FALSE)
     53       LOG(ERROR) << "Multiple CoInitialize() calls for thread " << thread_id_;
     54     else
     55       DCHECK_NE(RPC_E_CHANGED_MODE, hr_) << "Invalid COM thread model change";
     56 #endif
     57   }
     58 
     59   HRESULT hr_;
     60 #ifndef NDEBUG
     61   // In debug builds we use this variable to catch a potential bug where a
     62   // ScopedCOMInitializer instance is deleted on a different thread than it
     63   // was initially created on.  If that ever happens it can have bad
     64   // consequences and the cause can be tricky to track down.
     65   DWORD thread_id_;
     66 #endif
     67 
     68   DISALLOW_COPY_AND_ASSIGN(ScopedCOMInitializer);
     69 };
     70 
     71 }  // namespace win
     72 }  // namespace base
     73 
     74 #endif  // BASE_WIN_SCOPED_COM_INITIALIZER_H_
     75