ipc/glue/IPDLStructMember.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 file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_ipc_IPDLStructMember_h
   8 #define mozilla_ipc_IPDLStructMember_h
   9
  10 #include <type_traits>
  11 #include <utility>
  12 #include "mozilla/Attributes.h"
  13
  14 namespace mozilla::ipc {
  15
  16 // For types which are trivially default constructible, like `int`, force the
  17 // value constructor by wrapping the type in this struct.  This is an
  18 // implementation detail which will be hidden by the generated IPDL compiler
  19 // code.
  20 template <typename T>
  21 struct IPDLStructMemberWrapper {
  22   template <typename... Args>
  23   MOZ_IMPLICIT IPDLStructMemberWrapper(Args&&... aArgs)
  24       : mVal(std::forward<Args>(aArgs)...) {}
  25   MOZ_IMPLICIT operator T&() { return mVal; }
  26   MOZ_IMPLICIT operator const T&() const { return mVal; }
  27   T mVal{};
  28 };
  29
  30 template <typename T>
  31 using IPDLStructMember =
  32     std::conditional_t<std::is_trivially_default_constructible_v<T>,
  33                        IPDLStructMemberWrapper<T>, T>;
  34
  35 }  // namespace mozilla::ipc
  36
  37 #endif  // mozilla_ipc_IPDLStructMember_h