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Add-ons: add pointer traits

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flightgear::addons::shared_ptr_traits allows one to easily switch for
instance from an SGSharedPtr<T> to an std::shared_ptr<T> for "all" uses
of a particular T, and automatically have std::make_shared<T>(...) used
instead of SGSharedPtr<T>(new T(...)) when creating a shared instance of
T. This is interesting because std::make_shared<T>() allocates all
needed memory as one block, whereas std::shared_ptr<T>(new T(args...))
would perform at least two allocations (one for the object T and one for
the control block of the shared pointer).

This is done via static methods (one for each kind of smart pointer):

  shared_ptr_traits<SGSharedPtr<T>>::makeStrongRef()
  shared_ptr_traits<std::shared_ptr<T>>::makeStrongRef()

that forward their arguments in the same way as std::make_shared<T>().
This commit is contained in:
Florent Rougon 2018-01-02 00:35:50 +01:00
parent f1e0a4e43f
commit 843383fdc3
2 changed files with 68 additions and 0 deletions
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1
src/Add-ons/CMakeLists.txt
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@ -11,6 +11,7 @@ set(HEADERS addon_fwd.hxx
AddonManager.hxx
AddonVersion.hxx
exceptions.hxx
pointer_traits.hxx
)
flightgear_component(AddonManagement "${SOURCES}" "${HEADERS}")

67
src/Add-ons/pointer_traits.hxx Normal file
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@ -0,0 +1,67 @@
// -*- coding: utf-8 -*-
//
// pointer_traits.hxx --- Pointer traits classes
// Copyright (C) 2018 Florent Rougon
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#ifndef FG_ADDON_POINTER_TRAITS_HXX
#define FG_ADDON_POINTER_TRAITS_HXX
#include <memory>
#include <utility>
#include <simgear/structure/SGSharedPtr.hxx>
namespace flightgear
{
namespace addons
{
template <typename T>
struct shared_ptr_traits;
template <typename T>
struct shared_ptr_traits<SGSharedPtr<T>>
{
using element_type = T;
using strong_ref = SGSharedPtr<T>;
template <typename ...Args>
static strong_ref makeStrongRef(Args&& ...args)
{
return strong_ref(new T(std::forward<Args>(args)...));
}
};
template <typename T>
struct shared_ptr_traits<std::shared_ptr<T>>
{
using element_type = T;
using strong_ref = std::shared_ptr<T>;
template <typename ...Args>
static strong_ref makeStrongRef(Args&& ...args)
{
return std::make_shared<T>(std::forward<Args>(args)...);
}
};
} // of namespace addons
} // of namespace flightgear
#endif // of FG_ADDON_POINTER_TRAITS_HXX