base/win/scoped_propvariant.h

   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   const PROPVARIANT* ptr() const { return &pv_; }
  45
  46  private:
  47   PROPVARIANT pv_;
  48
  49   // Comparison operators for ScopedPropVariant are not supported at this point.
  50   bool operator==(const ScopedPropVariant&) const;
  51   bool operator!=(const ScopedPropVariant&) const;
  52   DISALLOW_COPY_AND_ASSIGN(ScopedPropVariant);
  53 };
  54
  55 }  // namespace win
  56 }  // namespace base
  57
  58 #endif  // BASE_WIN_SCOPED_PROPVARIANT_H_