xpcom/base/nsIInterfaceRequestorUtils.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef __nsInterfaceRequestorUtils_h
   8 #define __nsInterfaceRequestorUtils_h
   9
  10 #include "nsCOMPtr.h"
  11
  12 // a type-safe shortcut for calling the |GetInterface()| member function
  13 // T must inherit from nsIInterfaceRequestor, but the cast may be ambiguous.
  14 template <class T, class DestinationType>
  15 inline nsresult CallGetInterface(T* aSource, DestinationType** aDestination) {
  16   MOZ_ASSERT(aSource, "null parameter");
  17   MOZ_ASSERT(aDestination, "null parameter");
  18
  19   return aSource->GetInterface(NS_GET_TEMPLATE_IID(DestinationType),
  20                                reinterpret_cast<void**>(aDestination));
  21 }
  22
  23 class MOZ_STACK_CLASS nsGetInterface final : public nsCOMPtr_helper {
  24  public:
  25   nsGetInterface(nsISupports* aSource, nsresult* aError)
  26       : mSource(aSource), mErrorPtr(aError) {}
  27
  28   virtual nsresult NS_FASTCALL operator()(const nsIID&, void**) const override;
  29
  30  private:
  31   nsISupports* MOZ_NON_OWNING_REF mSource;
  32   nsresult* mErrorPtr;
  33 };
  34
  35 inline const nsGetInterface do_GetInterface(nsISupports* aSource,
  36                                             nsresult* aError = 0) {
  37   return nsGetInterface(aSource, aError);
  38 }
  39
  40 #endif  // __nsInterfaceRequestorUtils_h