include/library/lua-pin.hpp

   1 #ifndef _library__lua_pin__hpp__included__
   2 #define _library__lua_pin__hpp__included__
   3
   4 #include "lua-base.hpp"
   5
   6 namespace lua
   7 {
   8 /**
   9  * Pin of an object against Lua GC.
  10  */
  11 template<typename T> struct objpin
  12 {
  13 /**
  14  * Create a null pin.
  15  */
  16         objpin()
  17         {
  18                 _state = NULL;
  19                 obj = NULL;
  20         }
  21 /**
  22  * Create a new pin.
  23  *
  24  * Parameter _state: The state to pin the object in.
  25  * Parameter _object: The object to pin.
  26  */
  27         objpin(state& lstate, T* _object)
  28                 : _state(&lstate.get_master())
  29         {
  30                 _state->pushlightuserdata(this);
  31                 _state->pushvalue(-2);
  32                 _state->rawset(LUA_REGISTRYINDEX);
  33                 obj = _object;
  34         }
  35 /**
  36  * Delete a pin.
  37  */
  38         ~objpin() throw()
  39         {
  40                 if(obj) {
  41                         _state->pushlightuserdata(this);
  42                         _state->pushnil();
  43                         _state->rawset(LUA_REGISTRYINDEX);
  44                 }
  45         }
  46 /**
  47  * Copy ctor.
  48  */
  49         objpin(const objpin& p)
  50         {
  51                 _state = p._state;
  52                 obj = p.obj;
  53                 if(obj) {
  54                         _state->pushlightuserdata(this);
  55                         _state->pushlightuserdata(const_cast<objpin*>(&p));
  56                         _state->rawget(LUA_REGISTRYINDEX);
  57                         _state->rawset(LUA_REGISTRYINDEX);
  58                 }
  59         }
  60 /**
  61  * Assignment operator.
  62  */
  63         objpin& operator=(const objpin& p)
  64         {
  65                 if(_state == p._state && obj == p.obj)
  66                         return *this;
  67                 if(obj == p.obj)
  68                         throw std::logic_error("A Lua object can't be in two lua states at once");
  69                 if(obj) {
  70                         _state->pushlightuserdata(this);
  71                         _state->pushnil();
  72                         _state->rawset(LUA_REGISTRYINDEX);
  73                 }
  74                 _state = p._state;
  75                 if(p.obj) {
  76                         _state->pushlightuserdata(this);
  77                         _state->pushlightuserdata(const_cast<objpin*>(&p));
  78                         _state->rawget(LUA_REGISTRYINDEX);
  79                         _state->rawset(LUA_REGISTRYINDEX);
  80                 }
  81                 obj = p.obj;
  82                 return *this;
  83         }
  84 /**
  85  * Clear a pinned object.
  86  */
  87         void clear()
  88         {
  89                 if(obj) {
  90                         _state->pushlightuserdata(this);
  91                         _state->pushnil();
  92                         _state->rawset(LUA_REGISTRYINDEX);
  93                 }
  94                 _state = NULL;
  95                 obj = NULL;
  96         }
  97 /**
  98  * Get pointer to pinned object.
  99  *
 100  * Returns: The pinned object.
 101  */
 102         T* object() { return obj; }
 103 /**
 104  * Is non-null?
 105  */
 106         operator bool() { return obj != NULL; }
 107 /**
 108  * Smart pointer.
 109  */
 110         T& operator*() { if(obj) return *obj; throw std::runtime_error("Attempted to reference NULL Lua pin"); }
 111         T* operator->() { if(obj) return obj; throw std::runtime_error("Attempted to reference NULL Lua pin"); }
 112 /**
 113  * Push Lua value.
 114  */
 115         void luapush(state& lstate)
 116         {
 117                 lstate.pushlightuserdata(this);
 118                 lstate.rawget(LUA_REGISTRYINDEX);
 119         }
 120 private:
 121         T* obj;
 122         state* _state;
 123 };
 124
 125 template<typename T> void* unbox_any_pin(struct objpin<T>* pin)
 126 {
 127         return pin ? pin->object() : NULL;
 128 }
 129
 130 }
 131
 132 #endif