gecko-dev/xpcom/base/nsIInterfaceRequestorUtils.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef __nsInterfaceRequestorUtils_h
#define __nsInterfaceRequestorUtils_h

#include "nsCOMPtr.h"

// a type-safe shortcut for calling the |GetInterface()| member function
// T must inherit from nsIInterfaceRequestor, but the cast may be ambiguous.
template <class T, class DestinationType>
inline nsresult CallGetInterface(T* aSource, DestinationType** aDestination) {
  MOZ_ASSERT(aSource, "null parameter");
  MOZ_ASSERT(aDestination, "null parameter");

  return aSource->GetInterface(NS_GET_TEMPLATE_IID(DestinationType),
                               reinterpret_cast<void**>(aDestination));
}

class MOZ_STACK_CLASS nsGetInterface final : public nsCOMPtr_helper {
 public:
  nsGetInterface(nsISupports* aSource, nsresult* aError)
      : mSource(aSource), mErrorPtr(aError) {}

  virtual nsresult NS_FASTCALL operator()(const nsIID&, void**) const override;

 private:
  nsISupports* MOZ_NON_OWNING_REF mSource;
  nsresult* mErrorPtr;
};

inline const nsGetInterface do_GetInterface(nsISupports* aSource,
                                            nsresult* aError = 0) {
  return nsGetInterface(aSource, aError);
}

#endif  // __nsInterfaceRequestorUtils_h