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 #define LUABIND_BUILDING
  24
  25 #include <algorithm>
  26
  27 #include <luabind/lua_include.hpp>
  28
  29 #include <luabind/config.hpp>
  30 #include <luabind/weak_ref.hpp>
  31 #include <cassert>
  32
  33 namespace luabind {
  34
  35 namespace
  36 {
  37
  38   int weak_table_tag;
  39
  40 } // namespace unnamed
  41
  42 LUABIND_API void get_weak_table(lua_State* L)
  43 {
  44     lua_pushlightuserdata(L, &weak_table_tag);
  45     lua_rawget(L, LUA_REGISTRYINDEX);
  46
  47     if (lua_isnil(L, -1))
  48     {
  49         lua_pop(L, 1);
  50         lua_newtable(L);
  51         // metatable
  52         lua_newtable(L);
  53         lua_pushliteral(L, "__mode");
  54         lua_pushliteral(L, "v");
  55         lua_rawset(L, -3);
  56         // set metatable
  57         lua_setmetatable(L, -2);
  58
  59         lua_pushlightuserdata(L, &weak_table_tag);
  60         lua_pushvalue(L, -2);
  61         lua_rawset(L, LUA_REGISTRYINDEX);
  62     }
  63 }
  64
  65 } // namespace luabind
  66
  67 namespace luabind
  68 {
  69
  70     struct weak_ref::impl
  71     {
  72         impl(lua_State* main, lua_State* s, int index)
  73             : count(0)
  74             , state(main)
  75             , ref(0)
  76         {
  77             get_weak_table(s);
  78             lua_pushvalue(s, index);
  79             ref = luaL_ref(s, -2);
  80             lua_pop(s, 1);
  81         }
  82
  83         ~impl()
  84         {
  85             get_weak_table(state);
  86             luaL_unref(state, -1, ref);
  87             lua_pop(state, 1);
  88         }
  89
  90         int count;
  91         lua_State* state;
  92         int ref;
  93     };
  94
  95     weak_ref::weak_ref()
  96         : m_impl(0)
  97     {
  98     }
  99
 100     weak_ref::weak_ref(lua_State* main, lua_State* L, int index)
 101         : m_impl(new impl(main, L, index))
 102     {
 103         m_impl->count = 1;
 104     }
 105
 106     weak_ref::weak_ref(weak_ref const& other)
 107         : m_impl(other.m_impl)
 108     {
 109         if (m_impl) ++m_impl->count;
 110     }
 111
 112     weak_ref::~weak_ref()
 113     {
 114         if (m_impl && --m_impl->count == 0)
 115         {
 116             delete m_impl;
 117         }
 118     }
 119
 120     weak_ref& weak_ref::operator=(weak_ref const& other)
 121     {
 122         weak_ref(other).swap(*this);
 123         return *this;
 124     }
 125
 126     void weak_ref::swap(weak_ref& other)
 127     {
 128         std::swap(m_impl, other.m_impl);
 129     }
 130
 131     int weak_ref::id() const
 132     {
 133         assert(m_impl);
 134                 return m_impl->ref;
 135     }
 136
 137         // L may not be the same pointer as
 138         // was used when creating this reference
 139         // since it may be a thread that shares
 140         // the same globals table.
 141     void weak_ref::get(lua_State* L) const
 142     {
 143         assert(m_impl);
 144                 assert(L);
 145         get_weak_table(L);
 146         lua_rawgeti(L, -1, m_impl->ref);
 147         lua_remove(L, -2);
 148     }
 149
 150     lua_State* weak_ref::state() const
 151     {
 152         assert(m_impl);
 153         return m_impl->state;
 154     }
 155
 156 } // namespace luabind
 157