src/weak_ref.cpp

   1 // Copyright (c) 2004 Daniel Wallin and Arvid Norberg
   2
   3 // Permission is hereby granted, free of charge, to any person obtaining a
   4 // copy of this software and associated documentation files (the "Software"),
   5 // to deal in the Software without restriction, including without limitation
   6 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
   7 // and/or sell copies of the Software, and to permit persons to whom the
   8 // Software is furnished to do so, subject to the following conditions:
   9
  10 // The above copyright notice and this permission notice shall be included
  11 // in all copies or substantial portions of the Software.
  12
  13 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
  14 // ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
  15 // TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
  16 // PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
  17 // SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
  18 // ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  19 // ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
  21 // OR OTHER DEALINGS IN THE SOFTWARE.
  22
  23 #include <algorithm>
  24
  25 #include <luabind/lua_include.hpp>
  26
  27 #include <luabind/config.hpp>
  28 #include <luabind/weak_ref.hpp>
  29 #include <cassert>
  30
  31 namespace luabind {
  32
  33 // allocation code from lauxlib.c
  34 /******************************************************************************
  35 * Copyright (C) 1994-2003 Tecgraf, PUC-Rio.  All rights reserved.
  36 *
  37 * Permission is hereby granted, free of charge, to any person obtaining
  38 * a copy of this software and associated documentation files (the
  39 * "Software"), to deal in the Software without restriction, including
  40 * without limitation the rights to use, copy, modify, merge, publish,
  41 * distribute, sublicense, and/or sell copies of the Software, and to
  42 * permit persons to whom the Software is furnished to do so, subject to
  43 * the following conditions:
  44 *
  45 * The above copyright notice and this permission notice shall be
  46 * included in all copies or substantial portions of the Software.
  47 *
  48 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  49 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  50 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  51 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  52 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  53 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  54 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  55 ******************************************************************************/
  56
  57     namespace {
  58
  59         enum
  60         {
  61             freelist_ref = 1, count_ref = 2
  62         };
  63
  64         void get_weak_table(lua_State* L)
  65         {
  66             lua_pushliteral(L, "__luabind_weak_refs");
  67             lua_gettable(L, LUA_REGISTRYINDEX);
  68
  69             if (lua_isnil(L, -1))
  70             {
  71                 lua_pop(L, 1);
  72                 lua_newtable(L);
  73                 // metatable
  74                 lua_newtable(L);
  75                 lua_pushliteral(L, "__mode");
  76                 lua_pushliteral(L, "v");
  77                 lua_rawset(L, -3);
  78                 // set metatable
  79                 lua_setmetatable(L, -2);
  80                 lua_pushnumber(L, 0);
  81                 lua_rawseti(L, -2, freelist_ref);
  82                 lua_pushnumber(L, 2);
  83                 lua_rawseti(L, -2, count_ref);
  84
  85                 lua_pushliteral(L, "__luabind_weak_refs");
  86                 lua_pushvalue(L, -2);
  87                 lua_settable(L, LUA_REGISTRYINDEX);
  88             }
  89         }
  90
  91     } // namespace unnamed
  92
  93     struct weak_ref::impl
  94     {
  95         impl(lua_State* s, int index)
  96             : count(0)
  97             , state(s)
  98             , ref(0)
  99         {
 100             lua_pushvalue(s, index);
 101             get_weak_table(s);
 102
 103             lua_rawgeti(s, -1, freelist_ref);
 104             ref = (int)lua_tonumber(s, -1);
 105             lua_pop(s, 1);
 106
 107             if (ref == 0)
 108             {
 109                 lua_rawgeti(s, -1, count_ref);
 110                 ref = (int)lua_tonumber(s, -1) + 1;
 111                 lua_pop(s, 1);
 112                 lua_pushnumber(s, ref);
 113                 lua_rawseti(s, -2, count_ref);
 114             }
 115             else
 116             {
 117                 lua_rawgeti(s, -1, ref);
 118                 lua_rawseti(s, -2, freelist_ref);
 119             }
 120
 121             lua_pushvalue(s, -2); // duplicate value
 122             lua_rawseti(s, -2, ref);
 123             lua_pop(s, 2); // pop weakref table and value
 124         }
 125
 126         ~impl()
 127         {
 128             get_weak_table(state);
 129             lua_rawgeti(state, -1, freelist_ref);
 130             lua_rawseti(state, -2, ref);
 131             lua_pushnumber(state, ref);
 132             lua_rawseti(state, -2, freelist_ref);
 133             lua_pop(state, 1);
 134         }
 135
 136         int count;
 137         lua_State* state;
 138         int ref;
 139     };
 140
 141     weak_ref::weak_ref()
 142         : m_impl(0)
 143     {
 144     }
 145
 146     weak_ref::weak_ref(lua_State* L, int index)
 147         : m_impl(new impl(L, index))
 148     {
 149         m_impl->count = 1;
 150     }
 151
 152     weak_ref::weak_ref(weak_ref const& other)
 153         : m_impl(other.m_impl)
 154     {
 155         if (m_impl) ++m_impl->count;
 156     }
 157
 158     weak_ref::~weak_ref()
 159     {
 160         if (m_impl && --m_impl->count == 0)
 161         {
 162             delete m_impl;
 163         }
 164     }
 165
 166     weak_ref& weak_ref::operator=(weak_ref const& other)
 167     {
 168         weak_ref(other).swap(*this);
 169         return *this;
 170     }
 171
 172     void weak_ref::swap(weak_ref& other)
 173     {
 174         std::swap(m_impl, other.m_impl);
 175     }
 176
 177     void weak_ref::get() const
 178     {
 179         assert(m_impl);
 180         get_weak_table(m_impl->state);
 181         lua_rawgeti(m_impl->state, -1, m_impl->ref);
 182         lua_remove(m_impl->state, -2);
 183     }
 184
 185     lua_State* weak_ref::state() const
 186     {
 187         assert(m_impl);
 188         return m_impl->state;
 189     }
 190
 191 } // namespace luabind
 192