include/o3tl/unsafe_downcast.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #ifndef INCLUDED_O3TL_UNSAFE_DOWNCAST_HXX
  11 #define INCLUDED_O3TL_UNSAFE_DOWNCAST_HXX
  12
  13 #include <cassert>
  14 #include <type_traits>
  15
  16 namespace o3tl
  17 {
  18 // Do a downcast from polymorphic `BasePtr` to `DerivedPtr` when it is known that `p` is actually
  19 // pointing to an object of derived type (or is a nullptr).  This is potentially cheaper than
  20 // dynamic_cast and helps to avoid Coverity warnings about unchecked dynamic_cast.
  21 template <typename DerivedPtr, typename BasePtr>
  22 std::enable_if_t<
  23     (std::is_pointer_v<
  24          DerivedPtr> && std::is_pointer_v<BasePtr> && std::is_base_of_v<std::remove_pointer_t<BasePtr>, std::remove_pointer_t<DerivedPtr>>),
  25     DerivedPtr>
  26 unsafe_downcast(BasePtr p)
  27 {
  28     assert(p == nullptr || dynamic_cast<DerivedPtr>(p) != nullptr);
  29     return static_cast<DerivedPtr>(p);
  30 }
  31 }
  32
  33 #endif
  34
  35 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */