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1 /* lua smart pointers - version 0.2 (C only version) */
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2 /* (C) 2010 Daniel Adler */
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3
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4 #include "lua.h"
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5 #include "lauxlib.h"
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6
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7 #define LUA_SMARTPTR_LIBNAME "smartptr"
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8 #define LUA_SMARTPTR_TNAME "SmartPtr"
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9
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10 /*
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11 ** lua smart pointer
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12 **
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13 ** DESCRIPTION
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14 ** the smart pointer wraps lightuserdata (lua's object type for carrying raw pointer values)
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15 ** into a userdata structure where it also references a finalizer function, which will be called
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16 ** with the lightuserdata (not the userdata!) as an argument.
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17 **
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18 **
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19 ** LUA INTERFACE
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20 ** smartptr = newsmartptr(lightuserdata, function)
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21 ** setfinalizer(smartptr, function)
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22 ** lightuserdata = tolightuserdata(integer)
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23 **
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24 */
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25
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26 typedef struct
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27 {
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28 const void* pointer;
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29 int finalizer; /* lua reference */
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30 } lua_SmartPtr;
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31
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32 /*
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33 ** constructs a SmartPtr userdata lua object.
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34 **
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35 ** smartptr.new( pointer, finalizer )
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36 **
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37 ** @param pointer
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38 ** @param finalizer function ( to be called with pointer ) or nil
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39 ** @return SmartPtr userdata object
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40 */
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41
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42 int lua_smartptr_new(lua_State *L)
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43 {
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44 const void *ptr;
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45 int ref;
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46 lua_SmartPtr *sptr;
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47
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48 if (lua_gettop(L) != 2)
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49 luaL_error(L, "argument mismatch, usage:\n\tnewsmartptr( lightuserdata [, finalizer] )");
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50
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51 ptr = lua_topointer(L, 1);
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52 luaL_argcheck(L, lua_isfunction(L, 2), 2, "must be a finalizer function");
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53
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54 ref = luaL_ref(L, LUA_REGISTRYINDEX);
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55
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56 sptr = (lua_SmartPtr*) lua_newuserdata(L, sizeof(lua_SmartPtr) );
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57
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58 sptr->pointer = ptr;
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59 sptr->finalizer = ref;
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60
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61 luaL_getmetatable(L, LUA_SMARTPTR_TNAME);
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62 lua_setmetatable(L, -2);
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63
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64 return 1;
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65 }
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66
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67 /*
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68 ** update finalizer value on SmartPtr object
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69 **
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70 ** smartptr.setfinalizer(smartptr, newfinalizer)
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71 **
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72 ** @param smartptr object
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73 ** @param newfinalizer function or nil
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74 */
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75
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76 int lua_smartptr_setfinalizer(lua_State *L)
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77 {
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78 lua_SmartPtr* sptr = (lua_SmartPtr*) luaL_checkudata(L, 1, LUA_SMARTPTR_TNAME);
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79 if (lua_isnil(L, 2)) sptr->finalizer = LUA_REFNIL;
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80 lua_rawseti(L, LUA_REGISTRYINDEX, sptr->finalizer);
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81 return 0;
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82 }
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83
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84 /*
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85 ** call finalizer (internal through __gc event)
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86 **
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87 */
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88
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89 int lua_smartptr_callfinalizer(lua_State *L)
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90 {
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91 lua_SmartPtr* sptr = (lua_SmartPtr*) lua_topointer(L,1);
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92 int r = sptr->finalizer;
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93 if (r != LUA_REFNIL) {
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94 lua_rawgeti(L, LUA_REGISTRYINDEX, r);
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95 lua_pushlightuserdata(L, (void*) sptr->pointer);
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96 lua_call(L, 1, 0);
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97 luaL_unref(L, LUA_REGISTRYINDEX, r);
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98 }
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99 }
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100
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101 /*
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102 ** get pointer value
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103 **
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104 ** lua_smartptr_get(smartptr)
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105 **
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106 ** @return lightuserdata
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107 **
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108 */
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109
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110 int lua_smartptr_get(lua_State *L)
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111 {
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112 lua_SmartPtr* sptr = (lua_SmartPtr*) lua_topointer(L,1);
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113 lua_pushlightuserdata(L, (void*) sptr->pointer);
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114 return 1;
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115 }
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116
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117 /*
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118 ** lua c function tolightuserdata(integer)
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119 **
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120 ** @return lightuserdata
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121 **
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122 */
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123
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124 int lua_tolightuserdata(lua_State *L)
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125 {
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126 lua_Number number = lua_tonumber(L, 1);
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127 lua_pushlightuserdata(L, (void*) ( (unsigned long) number ) );
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128 return 1;
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129 }
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130
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131 void lua_smartptr_installmetatable(lua_State *L)
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132 {
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133 if ( luaL_newmetatable(L,LUA_SMARTPTR_TNAME) ) {
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134 lua_pushliteral(L, "__gc");
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135 lua_pushcfunction(L, lua_smartptr_callfinalizer);
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136 lua_settable(L, -3);
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137 lua_pushliteral(L, "__call");
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138 lua_pushcfunction(L, lua_smartptr_get);
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139 lua_settable(L, -3);
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140 lua_pop(L,1);
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141 }
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142 }
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143
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144 static const struct luaL_Reg luareg_smartptr[] =
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145 {
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146 { "new", lua_smartptr_new },
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147 { "setfinalizer", lua_smartptr_setfinalizer },
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148 { "tolightuserdata", lua_tolightuserdata },
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149 { NULL, NULL }
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150 };
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151
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152 LUALIB_API int luaopen_smartptr(lua_State *L)
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153 {
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154 lua_smartptr_installmetatable(L);
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155 luaL_register(L, LUA_SMARTPTR_LIBNAME, luareg_smartptr);
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156 return 0;
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157 }
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158
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