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/logging.h"
11 #include "base/macros.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:
ScopedPropVariant()20   ScopedPropVariant() { PropVariantInit(&pv_); }
21 
~ScopedPropVariant()22   ~ScopedPropVariant() { Reset(); }
23 
24   // Returns a pointer to the underlying PROPVARIANT for use as an out param in
25   // a function call.
Receive()26   PROPVARIANT* Receive() {
27     DCHECK_EQ(pv_.vt, VT_EMPTY);
28     return &pv_;
29   }
30 
31   // Clears the instance to prepare it for re-use (e.g., via Receive).
Reset()32   void Reset() {
33     if (pv_.vt != VT_EMPTY) {
34       HRESULT result = PropVariantClear(&pv_);
35       DCHECK_EQ(result, S_OK);
36     }
37   }
38 
get()39   const PROPVARIANT& get() const { return pv_; }
ptr()40   const PROPVARIANT* ptr() const { return &pv_; }
41 
42  private:
43   PROPVARIANT pv_;
44 
45   // Comparison operators for ScopedPropVariant are not supported at this point.
46   bool operator==(const ScopedPropVariant&) const;
47   bool operator!=(const ScopedPropVariant&) const;
48   DISALLOW_COPY_AND_ASSIGN(ScopedPropVariant);
49 };
50 
51 }  // namespace win
52 }  // namespace base
53 
54 #endif  // BASE_WIN_SCOPED_PROPVARIANT_H_
55