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      1 // Copyright (c) 2013 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_PROPVARIANT_H_
      6 #define BASE_WIN_SCOPED_PROPVARIANT_H_
      7 
      8 #include <propidl.h>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/logging.h"
     12 
     13 namespace base {
     14 namespace win {
     15 
     16 // A PROPVARIANT that is automatically initialized and cleared upon respective
     17 // construction and destruction of this class.
     18 class ScopedPropVariant {
     19  public:
     20   ScopedPropVariant() {
     21     PropVariantInit(&pv_);
     22   }
     23 
     24   ~ScopedPropVariant() {
     25     Reset();
     26   }
     27 
     28   // Returns a pointer to the underlying PROPVARIANT for use as an out param in
     29   // a function call.
     30   PROPVARIANT* Receive() {
     31     DCHECK_EQ(pv_.vt, VT_EMPTY);
     32     return &pv_;
     33   }
     34 
     35   // Clears the instance to prepare it for re-use (e.g., via Receive).
     36   void Reset() {
     37     if (pv_.vt != VT_EMPTY) {
     38       HRESULT result = PropVariantClear(&pv_);
     39       DCHECK_EQ(result, S_OK);
     40     }
     41   }
     42 
     43   const PROPVARIANT& get() const { return pv_; }
     44 
     45   const PROPVARIANT* operator&() const { return &pv_; }
     46 
     47  private:
     48   PROPVARIANT pv_;
     49 
     50   // Comparison operators for ScopedPropVariant are not supported at this point.
     51   bool operator==(const ScopedPropVariant&) const;
     52   bool operator!=(const ScopedPropVariant&) const;
     53   DISALLOW_COPY_AND_ASSIGN(ScopedPropVariant);
     54 };
     55 
     56 }  // namespace win
     57 }  // namespace base
     58 
     59 #endif  // BASE_WIN_SCOPED_PROPVARIANT_H_
     60