src/irr_ptr.h

   1 /*
   2 Minetest
   3 Copyright (C) 2018 numzero, Lobachevskiy Vitaliy <numzer0@yandex.ru>
   4
   5 This program is free software; you can redistribute it and/or modify
   6 it under the terms of the GNU Lesser General Public License as published by
   7 the Free Software Foundation; either version 2.1 of the License, or
   8 (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU Lesser General Public License for more details.
  14
  15 You should have received a copy of the GNU Lesser General Public License along
  16 with this program; if not, write to the Free Software Foundation, Inc.,
  17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18 */
  19
  20 #pragma once
  21 #include <type_traits>
  22 #include "irrlichttypes.h"
  23 #include "IReferenceCounted.h"
  24
  25 /** Shared pointer for IrrLicht objects.
  26  *
  27  * It should only be used for user-managed objects, i.e. those created with
  28  * the @c new operator or @c create* functions, like:
  29  * `irr_ptr<scene::IMeshBuffer> buf{new scene::SMeshBuffer()};`
  30  *
  31  * It should *never* be used for engine-managed objects, including
  32  * those created with @c addTexture and similar methods.
  33  */
  34 template <class ReferenceCounted,
  35                 class = typename std::enable_if<std::is_base_of<IReferenceCounted,
  36                                 ReferenceCounted>::value>::type>
  37 class irr_ptr
  38 {
  39         ReferenceCounted *value = nullptr;
  40
  41         /** Drops stored pointer replacing it with the given one.
  42          * @note Copy semantics: reference counter *is* increased.
  43          */
  44         void grab(ReferenceCounted *object)
  45         {
  46                 if (object)
  47                         object->grab();
  48                 reset(object);
  49         }
  50
  51 public:
  52         irr_ptr() {}
  53
  54         irr_ptr(std::nullptr_t) noexcept {}
  55
  56         irr_ptr(const irr_ptr &b) noexcept { grab(b.get()); }
  57
  58         irr_ptr(irr_ptr &&b) noexcept { reset(b.release()); }
  59
  60         template <typename B, class = typename std::enable_if<std::is_convertible<B *,
  61                                               ReferenceCounted *>::value>::type>
  62         irr_ptr(const irr_ptr<B> &b) noexcept
  63         {
  64                 grab(b.get());
  65         }
  66
  67         template <typename B, class = typename std::enable_if<std::is_convertible<B *,
  68                                               ReferenceCounted *>::value>::type>
  69         irr_ptr(irr_ptr<B> &&b) noexcept
  70         {
  71                 reset(b.release());
  72         }
  73
  74         /** Constructs a shared pointer out of a plain one
  75          * @note Move semantics: reference counter is *not* increased.
  76          */
  77         explicit irr_ptr(ReferenceCounted *object) noexcept { reset(object); }
  78
  79         ~irr_ptr() { reset(); }
  80
  81         irr_ptr &operator=(const irr_ptr &b) noexcept
  82         {
  83                 grab(b.get());
  84                 return *this;
  85         }
  86
  87         irr_ptr &operator=(irr_ptr &&b) noexcept
  88         {
  89                 reset(b.release());
  90                 return *this;
  91         }
  92
  93         template <typename B, class = typename std::enable_if<std::is_convertible<B *,
  94                                               ReferenceCounted *>::value>::type>
  95         irr_ptr &operator=(const irr_ptr<B> &b) noexcept
  96         {
  97                 grab(b.get());
  98                 return *this;
  99         }
 100
 101         template <typename B, class = typename std::enable_if<std::is_convertible<B *,
 102                                               ReferenceCounted *>::value>::type>
 103         irr_ptr &operator=(irr_ptr<B> &&b) noexcept
 104         {
 105                 reset(b.release());
 106                 return *this;
 107         }
 108
 109         ReferenceCounted &operator*() const noexcept { return *value; }
 110         ReferenceCounted *operator->() const noexcept { return value; }
 111         explicit operator ReferenceCounted *() const noexcept { return value; }
 112         explicit operator bool() const noexcept { return !!value; }
 113
 114         /** Returns the stored pointer.
 115          */
 116         ReferenceCounted *get() const noexcept { return value; }
 117
 118         /** Returns the stored pointer, erasing it from this class.
 119          * @note Move semantics: reference counter is not changed.
 120          */
 121         ReferenceCounted *release() noexcept
 122         {
 123                 ReferenceCounted *object = value;
 124                 value = nullptr;
 125                 return object;
 126         }
 127
 128         /** Drops stored pointer replacing it with the given one.
 129          * @note Move semantics: reference counter is *not* increased.
 130          */
 131         void reset(ReferenceCounted *object = nullptr) noexcept
 132         {
 133                 if (value)
 134                         value->drop();
 135                 value = object;
 136         }
 137 };