src/lqt_common.cpp

   1 /*
   2  * Copyright (c) 2007 Mauro Iazzi
   3  *
   4  * Permission is hereby granted, free of charge, to any person
   5  * obtaining a copy of this software and associated documentation
   6  * files (the "Software"), to deal in the Software without
   7  * restriction, including without limitation the rights to use,
   8  * copy, modify, merge, publish, distribute, sublicense, and/or sell
   9  * copies of the Software, and to permit persons to whom the
  10  * Software is furnished to do so, subject to the following
  11  * conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be
  14  * included in all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  17  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  18  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  19  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  20  * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  21  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  22  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  23  * OTHER DEALINGS IN THE SOFTWARE.
  24  *
  25  */
  26
  27 #include "lqt_common.hpp"
  28 #include <cstring>
  29
  30 #define LQT_FIXEDINDEX(i)  (i<0?(1+lua_gettop(L)+i):i)
  31 #define LQT_MAX_ARGS 50
  32
  33 //#include <QDebug>
  34 #ifndef SEE_STACK
  35 # define SEE_STACK(L, j) for (int j=1;j<=lua_gettop(L);j++) { qDebug() << j << '=' << luaL_typename(L, j) << '@' << lua_topointer (L, j); }
  36 #endif
  37
  38 // TODO
  39 //
  40 //  - add a metatable for void* which always results in nil and possibly
  41 //    accounts for reassigning the userdata to the right metatable.
  42 //  - proper descending down the dependency tree for indexing, and proper
  43 //    handling of missing binds
  44 //
  45
  46
  47 //#include <iostream>
  48 //using namespace std;
  49
  50 int check_gc(lua_State*L){
  51         lua_newtable(L);
  52         lua_getglobal(L, "print");
  53         lua_setfield(L, -2, "__gc");
  54         lua_setmetatable(L, -2);
  55         return 0;
  56 }
  57
  58 void *get_buffer(lua_State *L, size_t sz) {
  59 #if 1
  60         void *ret = lua_newuserdata(L, sz);
  61   //check_gc(L);
  62         lua_pushlightuserdata(L, ret);
  63         lua_insert(L, -2);
  64         lua_settable(L, LUA_REGISTRYINDEX);
  65 #else
  66         void *ret = malloc(sz);
  67         cout << ret << endl;
  68 #endif
  69         return ret;
  70 }
  71
  72 int& lqtL_tointref (lua_State *L, int i) {
  73   i = LQT_FIXEDINDEX(i);
  74         int *ret = NULL;
  75         ret = (int*)get_buffer(L, sizeof(int));
  76         *ret = lua_type(L, i)==LUA_TNUMBER?lua_tointeger(L, i):0;
  77         //cout << "interef " << ret << endl;
  78         return *ret;
  79 }
  80 void lqtL_pusharguments (lua_State *L, char **argv) {
  81         int i = 0;
  82         lua_newtable(L);
  83         for (i=0;*argv && i<LQT_MAX_ARGS;argv++,i++) {
  84     lua_pushstring(L, *argv);
  85                 lua_rawseti(L, -2, i+1);
  86         }
  87         return;
  88 }
  89 char** lqtL_toarguments (lua_State *L, int index) {
  90         index = LQT_FIXEDINDEX(index);
  91         char **ret;
  92         const char *str;
  93         int retlen = 0;
  94         size_t strlen = 0;
  95         int i = 0;
  96         retlen = lua_objlen(L, index);
  97         ret = (char**)get_buffer(L, sizeof(char*)*(retlen+1));
  98         //cout << retlen << endl;
  99         for (i=0;i<retlen;i++) {
 100                 lua_rawgeti(L, index, i+1);
 101                 if (lua_isstring(L, -1)) {
 102                         str = lua_tolstring(L, -1, &strlen);
 103                         ret[i] = (char*)get_buffer(L, sizeof(char)*(strlen+1));
 104                         strncpy(ret[i], str, strlen+1);
 105                         //cout << "arg " << (void*)ret[i] << ' ' << ret[i] << endl;
 106                 } else {
 107                         strlen = 0;
 108       str = "\0";
 109                         ret[i] = (char*)get_buffer(L, sizeof(char)*(strlen+1));
 110                         strncpy(ret[i], str, strlen+1);
 111                         //cout << "Zarg " << (void*)ret[i] << ' ' << ret[i] << endl;
 112                 }
 113                 lua_pop(L, 1);
 114         }
 115   ret[retlen] = NULL;
 116         //cout << "arg[] " << ret << endl;
 117         return ret;
 118 }
 119 bool lqtL_testarguments (lua_State *L, int index) {
 120         return (bool)lua_istable(L, index);
 121 }
 122
 123 void lqtL_setvoidmetatable (lua_State *L, int i, const char *t = 0) {
 124         i = LQT_FIXEDINDEX(i);
 125         if (luaL_newmetatable(L, "void*")) {
 126                 lua_newtable(L);
 127                 lua_setfield(L, -2, "__index");
 128                 lua_pushstring(L, "void*");
 129                 lua_setfield(L, -2, "__qtype");
 130         }
 131         lua_setmetatable(L, i);
 132         if (t!=0) {
 133                 lua_newtable(L);
 134                 lua_pushstring(L, t);
 135                 lua_setfield(L, -2, "__unknown_type");
 136                 lua_setfenv(L, i);
 137         }
 138 }
 139
 140 void lqtL_getpointers (lua_State *L) {
 141   lua_getfield(L, LUA_REGISTRYINDEX, LQT_POINTERS);
 142   if (!lua_istable(L, -1)) {
 143     //cout << "Registry Pointers created" << endl;
 144     lua_pop(L, 1);
 145     lua_newtable(L);
 146     lua_newtable(L);
 147     lua_pushstring(L, "kv");
 148     lua_setfield(L, -2, "__mode");
 149     lua_setmetatable(L, -2);
 150     lua_pushvalue(L, -1);
 151     lua_setfield(L, LUA_REGISTRYINDEX, LQT_POINTERS);
 152   }
 153   return;
 154 }
 155
 156 int lqtL_reusepointer (lua_State *L, const void *p, const char *t) {
 157   lqtL_getpointers(L);
 158   lua_pushlightuserdata(L, const_cast<void*>(p));
 159   lua_gettable(L, -2);
 160   if (lqtL_testudata(L, -1, t) && (p==*(const void**)lua_touserdata(L, -1))) {
 161                 lua_remove(L, -2);
 162                 //qDebug();
 163                 //qDebug() << "reused" << p << "in" << lua_touserdata(L, -1) << t;
 164                 //lua_getmetatable(L, -1);luaL_getmetatable(L, t);
 165                 //qDebug() << "meta" << lua_topointer(L, -2) << "type" << lua_topointer(L, -1);
 166                 //lua_pop(L, 2);
 167     return 1;
 168   }
 169   lua_pop(L, 2);
 170   return 0;
 171 }
 172
 173 void lqtL_pushpointer (lua_State *L, const void *obj, const char *t) {
 174   const void **objp = (const void**)lua_newuserdata(L, sizeof(const void *));
 175   *objp = 0;
 176   lua_getfield(L, LUA_REGISTRYINDEX, t);
 177   if (lua_istable(L, -1)) {
 178                 lua_setmetatable(L, -2);
 179                 lua_newtable(L);
 180                 lua_setfenv(L, -2);
 181   } else {
 182     //cout << "NO metatable given" << endl;
 183     // TODO: add a fallback?
 184     lua_pop(L, 1);
 185                 lqtL_setvoidmetatable(L, -1, t);
 186   }
 187   *objp = obj;
 188   //cout << "pushed " << objp << ' ' << obj << endl;
 189 }
 190
 191 void lqtL_setpointer (lua_State *L, int i, const void *obj) {
 192   int index = i<0?(1+lua_gettop(L)+i):i;
 193   //cout << lua_gettop(L) << ' ' << i << ' ' << index << endl;
 194   lqtL_getpointers(L);
 195   lua_pushlightuserdata(L, const_cast<void *>(obj));
 196   lua_pushvalue(L, index);
 197   lua_settable(L, -3);
 198   lua_pop(L, 1);
 199   return;
 200 }
 201 void lqtL_unsetpointer (lua_State *L, const void *obj) {
 202   lqtL_getpointers(L);
 203   lua_pushlightuserdata(L, const_cast<void *>(obj));
 204   lua_pushnil(L);
 205   lua_settable(L, -3);
 206   lua_pop(L, 1);
 207   return;
 208 }
 209
 210 // TODO: don't need, it's debug
 211 void * lqtL_topointer (lua_State *L, int i) {
 212   void * ret = NULL;
 213   ret = lua_touserdata(L, i);
 214   ret = (ret==0)?0:*static_cast<void**>(ret);
 215   return ret;
 216 }
 217
 218 void lqtL_unmanageudata (lua_State *L, int i) {
 219   if (!lua_isuserdata(L, i)) return;
 220   lua_getfenv(L, i);
 221   if (lua_istable(L, -1)) {
 222     lua_pushnil(L);
 223     lua_setfield(L, -2, "__gc");
 224   }
 225   lua_pop(L, 1);
 226   return;
 227 }
 228 void lqtL_manageudata (lua_State *L, int index) {
 229         //luaL_checkstack(L, 20, "");
 230   index = LQT_FIXEDINDEX(index);
 231   if (!lua_isuserdata(L, index)) return;
 232   lua_getfield(L, index, "delete");
 233   if (!lua_isfunction(L, -1)) {
 234     lua_pop(L, 1);
 235     return;
 236   }
 237   lua_getfenv(L, index);
 238   if (!lua_istable(L, -1)) {
 239     lua_pop(L, 1);
 240   //if (1) {
 241     lua_newtable(L);
 242     lua_pushvalue(L, -1);
 243     lua_setfenv(L, index);
 244   }
 245   lua_insert(L, -2);
 246   lua_setfield(L, -2, "__gc");
 247   lua_pop(L, 1);
 248   return;
 249 }
 250 void lqtL_pushudata (lua_State *L, const void *obj, const char *t) {
 251   // TODO: make the udata unique
 252   //cout << endl << "pushing udata " << obj << " with type " << t << endl;
 253
 254   lua_checkstack(L, 5);
 255   if (1) {
 256     if (lqtL_reusepointer(L, obj, t)) {
 257       //cout << obj << " reused " << t  << endl;
 258       return;
 259     }
 260                 //cout << obj << " NOT reused " << t  << endl;
 261   } else {
 262     lqtL_getpointers(L);
 263     lua_pushlightuserdata(L, const_cast<void *>(obj));
 264     lua_gettable(L, -2);
 265     if (0) {
 266       //cout << lua_gettop(L) << endl;
 267       lua_getglobal(L, "print");
 268       if (lua_getmetatable(L, -2)) {
 269         //cout << "metatable "; // << lua_tostring(L, -1) << endl << endl;
 270         lua_call(L, 1, 0);
 271       } else {
 272         //cout << "no metatable" << endl;
 273         lua_pop(L, 1);
 274       }
 275       //cout << lua_gettop(L) << endl;
 276       lua_getglobal(L, "print");
 277       lua_getfield(L, LUA_REGISTRYINDEX, t);
 278       //cout << "registry  "; // << lua_tostring(L, -1) << endl; lua_pop(L, 1);
 279       lua_call(L, 1, 0);
 280     } else if (0) {
 281       //cout << lua_gettop(L) << endl;
 282       if (lua_getmetatable(L, -1)) {
 283         lua_getfield(L, LUA_REGISTRYINDEX, t);
 284         //cout << (bool)lua_equal(L, -1, -2) << endl;
 285         lua_getglobal(L, "print");
 286         lua_insert(L, -3);
 287         lua_call(L, 2, 0);
 288       } else {
 289         //cout << "no metatable" << endl;
 290         lua_pop(L, 1);
 291       }
 292     }
 293     if (lqtL_testudata(L, -1, t)) {
 294       //cout << obj << " reused" << endl;
 295       lua_remove(L, -2);
 296       return;
 297     } else {
 298       //cout << luaL_typename(L, -1) << " testudata failed " << lua_touserdata(L, -1) << ' ' << lqtL_topointer(L, -1) << endl;
 299     }
 300     lua_pop(L, 2);
 301   }
 302
 303   if (1) {
 304     lqtL_pushpointer(L, obj, t);
 305   } else {
 306     const void **objp = (const void**)lua_newuserdata(L, sizeof(const void *));
 307     *objp = 0;
 308     lua_getfield(L, LUA_REGISTRYINDEX, t);
 309     if (lua_istable(L, -1)) {
 310       lua_setmetatable(L, -2);
 311     } else {
 312       //cout << "NO metatable given" << endl;
 313       lua_pop(L, 1);
 314       // TODO: add a fallback?
 315     }
 316     *objp = obj;
 317     //cout << "pushed " << objp << ' ' << obj << endl;
 318   }
 319   //cout << lua_gettop(L) << endl;
 320   if (1) {
 321     lqtL_setpointer(L, -1, obj);
 322   } else {
 323     lua_getfield(L, LUA_REGISTRYINDEX, LQT_POINTERS);
 324     lua_pushlightuserdata(L, const_cast<void *>(obj));
 325     lua_pushvalue(L, -3);
 326     lua_settable(L, -3);
 327     lua_pop(L, 1);
 328   }
 329   //cout << lua_gettop(L) << endl;
 330 }
 331 void lqtL_passudata (lua_State *L, const void *obj, const char *t) {
 332         //cout << "passing: " << obj << " " << t << endl;
 333   lqtL_pushudata(L, obj, t);
 334   lqtL_manageudata(L, -1);
 335 }
 336
 337
 338 int lqtL_derivesfrom (lua_State *L, int i, const char *t) {
 339         int ret = 0;
 340         int oldtop = lua_gettop(L);
 341         i = LQT_FIXEDINDEX(i);
 342
 343   if (!lua_istable(L, i)) {
 344                 return 0;
 345         }
 346
 347         luaL_checkstack(L, 1, "cannot grow stack for checking object type");
 348
 349         //qDebug() << "given a table" << lua_topointer(L, i);
 350         lua_getfield(L, LUA_REGISTRYINDEX, t);
 351         //qDebug() << "table" << t << lua_topointer(L, -1);
 352         ret = lua_equal(L, i, -1);
 353         //qDebug() << "same as" << t << "?" << (bool)ret;
 354
 355         /*
 356         lua_settop(L, oldtop);
 357
 358         return ret;
 359         // */
 360
 361         if (!ret) {
 362                 lua_pop(L, 1);
 363                 luaL_checkstack(L, 13, "cannot grow stack for checking object type"); // FIXME: is it enough?
 364                 lua_getfield(L, i, "__base");
 365
 366                 if (!lua_istable(L, -1)) {
 367                         lua_pop(L, 1);
 368                         ret = 0;
 369                 } else {
 370                         lua_getfield(L, -1, t);
 371                         ret = lua_isnil(L, -1)?0:1;
 372                         //if (ret) qDebug() << (lua_toboolean(L, -1)?"directly":"INDIRECTLY") << "derives from" << t;
 373                         // DANGER: order of control expression is important
 374                         while ((ret == 0) && (lua_next(L, -2) != 0)) {
 375                                 if (!lua_istable(L, -1)) {
 376                                         lua_pop(L, 1);
 377                                         lua_pushvalue(L, -1);
 378                                         lua_gettable(L, LUA_REGISTRYINDEX);
 379                                         if (lua_istable(L, -1)) {
 380                                                 lua_pushvalue(L, -2);
 381                                                 lua_pushvalue(L, -2);
 382                                                 lua_settable(L, -5);
 383                                         }
 384                                 }
 385                                 if (lua_istable(L, -1)) {
 386                                         ret = lqtL_derivesfrom(L, -1, t);
 387                                 }
 388                                 lua_pop(L, 1);
 389                         }
 390                 }
 391         }
 392
 393         lua_settop(L, oldtop);
 394
 395         return ret;
 396 }
 397
 398 bool lqtL_testudata (lua_State *L, int i, const char *t) {
 399         //qDebug() << "================ testudata" << t;
 400         //luaL_checkstack(L, 99, "");
 401         i = LQT_FIXEDINDEX(i);
 402         bool ret = false;
 403   if (lua_getmetatable(L, i)) {
 404                 //SEE_STACK(L, pippo);
 405                 //SEE_STACK(L, pippo);
 406                 if (0) {
 407                 lua_getfield(L, LUA_REGISTRYINDEX, "QEvent*");
 408                 if (0 && lua_istable(L, -1)) {
 409                         lua_getfield(L, -1, "__qtype");
 410       //SEE_STACK(L, pippo);
 411                         lua_pop(L, 1);
 412                 }
 413                 lua_pop(L, 2);
 414                 }
 415     ret = (bool) lqtL_derivesfrom(L, -1, t);
 416
 417                 //qDebug() << "derives?" << ret;
 418                 if (!ret && lqtL_derivesfrom(L, -1, "void*")) {
 419                         //cout << "checking for a generic void* pointer" << endl;
 420                         //*
 421                         luaL_checkstack(L, 3, "cannot check void* real type");
 422       lua_getfenv(L, i);
 423                         lua_getfield(L, -1, "__unknown_type");
 424                         //TODO: assign dynamically?
 425                         lua_pushstring(L, t);
 426                         ret = (bool)lua_equal(L, -1, -2);
 427                         lua_pop(L, 3);
 428                         // */
 429                         // FIXME: deleting makes QMetaObjects not work
 430                         //ret = true;
 431                 }
 432                 lua_pop(L, 1);
 433         } else {
 434         }
 435         //cout << t << (ret?"":" NOT") <<" found" << endl;
 436         return ret;
 437         /*
 438   bool ret = false;
 439         int oldtop = lua_gettop(L);
 440         lua_getfield(L, LUA_REGISTRYINDEX, t);
 441   if (lua_getmetatable(L, i)) {
 442     ret = (bool)lua_equal(L, -1, -2);
 443                 if (!ret) {
 444                         lua_remove(L, -2);
 445                         ret = lqTL_derivesfrom(L, -1, t);
 446                 }
 447   }
 448         lua_settop(L, oldtop);
 449   return ret;
 450         */
 451 }
 452 //*
 453
 454 int lqtL_pushtype (lua_State *L, int i) {
 455         int type = lua_type(L, i);
 456         if (type != LUA_TUSERDATA) {
 457                 lua_pushstring(L, lua_typename(L, type));
 458         } else {
 459     lua_getfield(L, i, "__qtype");
 460                 if (!lua_isstring(L, -1)) {
 461                         lua_pop(L, 1);
 462                         lua_pushstring(L, "<unknown>");
 463                 }
 464         }
 465         return 1;
 466 }
 467
 468 void * lqtL_checkudata (lua_State *L, int i, const char *t) {
 469         if (lqtL_testudata(L, i, t)) {
 470                 return lua_touserdata(L, i);
 471         } else {
 472                 lua_pushstring(L, "Fatal error: userdata type mismatch. requested ");
 473                 lua_pushstring(L, t);
 474                 lua_pushstring(L, " found ");
 475     lqtL_pushtype(L, i);
 476                 lua_concat(L, 4);
 477                 lua_error(L);
 478         }
 479         return 0;
 480 }
 481 //*/
 482 void * lqtL_toudata (lua_State *L, int i, const char *t) {
 483   void * ret = NULL;
 484   if (lqtL_testudata(L, i, t)) {
 485     ret = *static_cast<void**>(lua_touserdata(L, i));
 486   }
 487   return ret;
 488 }
 489
 490 void lqtL_pushenum (lua_State *L, int v, const char *e) {
 491   lua_getfield(L, LUA_REGISTRYINDEX, LQT_ENUMS);
 492   if (lua_istable(L, -1)) {
 493                 //qDebug() << "LQT_ENUMS is a table";
 494     lua_getfield(L, -1, e);
 495     lua_remove(L, -2);
 496   } else {
 497                 //qDebug() << "LQT_ENUMS is NOT a table";
 498         }
 499   lua_pushinteger(L, v);
 500   if (lua_istable(L, -2)) {
 501                 //qDebug() << "getting translation";
 502     lua_gettable(L, -2);
 503   } else {
 504                 //qDebug() << "no translation table for" << e;
 505         }
 506   lua_remove(L, -2);
 507 }
 508 bool lqtL_isenum (lua_State *L, int i, const char *e) {
 509   bool ret = false;
 510   if (lua_type(L, i)==LUA_TNUMBER) {
 511     ret = (lua_tointeger(L, i)==lua_tonumber(L, i));
 512   } else if (lua_type(L, i)==LUA_TSTRING) {
 513     lua_getfield(L, LUA_REGISTRYINDEX, LQT_ENUMS);
 514     if (lua_istable(L, -1)) {
 515       lua_getfield(L, -1, e);
 516       lua_remove(L, -2);
 517     }
 518     lua_pushvalue(L, i);
 519     if (lua_istable(L, -2)) {
 520       lua_gettable(L, -2);
 521     }
 522     if (lua_type(L, -1)==LUA_TNUMBER) {
 523       ret = (lua_tointeger(L, -1)==lua_tonumber(L, -1));
 524     }
 525     lua_pop(L, 2);
 526   }
 527   return ret;
 528 }
 529 int lqtL_toenum (lua_State *L, int i, const char *e) {
 530   int ret = -1;
 531   if (lua_type(L, i)==LUA_TNUMBER) {
 532     ret = lua_tointeger(L, i);
 533   } else if (lua_type(L, i)==LUA_TSTRING) {
 534     lua_getfield(L, LUA_REGISTRYINDEX, LQT_ENUMS);
 535     if (lua_istable(L, -1)) {
 536       lua_getfield(L, -1, e);
 537       lua_remove(L, -2);
 538     }
 539     lua_pushvalue(L, i);
 540     if (lua_istable(L, -2)) {
 541       lua_gettable(L, -2);
 542     }
 543     if (lua_type(L, -1)==LUA_TNUMBER) {
 544       ret = lua_tointeger(L, -1);
 545     }
 546     lua_pop(L, 2);
 547   }
 548   return ret;
 549 }
 550
 551 int lqtL_baseindex (lua_State *L, int index, int key) {
 552         int ret = 0;
 553         int oldtop = lua_gettop(L);
 554         index = LQT_FIXEDINDEX(index);
 555         key = LQT_FIXEDINDEX(key);
 556
 557   if (!lua_istable(L, index)) {
 558                 return 0;
 559         }
 560
 561         luaL_checkstack(L, 1, "cannot grow stack for retrieving member");
 562
 563         lua_pushvalue(L, key);
 564         lua_gettable(L, index);
 565
 566         if (!lua_isnil(L, -1)) {
 567                 ret = 1;
 568         } else {
 569                 luaL_checkstack(L, 7, "cannot grow stack for retrieving member"); // FIXME: is it enough?
 570                 lua_getfield(L, index, "__base");
 571
 572                 if (!lua_istable(L, -1)) {
 573                         lua_pop(L, 2);
 574                         ret = 0;
 575                 } else {
 576                         lua_insert(L, -2);
 577                         // DANGER: order of control expression is important
 578                         while ((ret == 0) && (lua_next(L, -2) != 0)) {
 579                                 if (!lua_istable(L, -1) && lua_isboolean(L, -1) && lua_toboolean(L, -1)) {
 580                                         lua_pop(L, 1);
 581                                         lua_pushvalue(L, -1);
 582                                         lua_gettable(L, LUA_REGISTRYINDEX);
 583                                         if (lua_istable(L, -1)) {
 584                                                 lua_pushvalue(L, -2);
 585                                                 lua_pushvalue(L, -2);
 586                                                 lua_settable(L, -5);
 587                                         }
 588                                 }
 589                                 if (lua_istable(L, -1)) {
 590                                         ret = lqtL_baseindex(L, -1, key);
 591                                 }
 592                                 if (ret == 0) {
 593                                         lua_pop(L, 1);
 594                                 }
 595                         }
 596                 }
 597         }
 598
 599         if (ret != 0) {
 600     lua_insert(L, oldtop+1);
 601         }
 602         lua_settop(L, oldtop+ret);
 603
 604         return ret;
 605 }
 606
 607 int lqtL_index (lua_State *L) {
 608         lua_settop(L, 2);
 609         luaL_checkstack(L, 1, "cannot grow stack for retrieving member");
 610         if (!lua_getmetatable(L, 1)) {
 611                 return 0;
 612         }
 613
 614         return lqtL_baseindex(L, 3, 2);
 615 /*
 616         luaL_checkstack(L, 2, "cannot grow stack for retrieving member");
 617   lua_getmetatable(L, 1);
 618   if (lua_istable(L, -1)) {
 619     lua_pushvalue(L, 2);
 620     lua_gettable(L, -2);
 621   } else {
 622     lua_pushnil(L);
 623   }
 624   lua_remove(L, -2);
 625   return 1;
 626 */
 627 }
 628
 629 int lqtL_newindex (lua_State *L) {
 630         if (!lua_getmetatable(L, 1)) {
 631                 return 0;
 632         }
 633   if (lua_istable(L, -1)) {
 634     lua_pushvalue(L, 2);
 635     lua_pushvalue(L, 3);
 636     lua_settable(L, -3);
 637     lua_pop(L, 1);
 638   }
 639   return 0;
 640 }
 641
 642 int lqtL_gc (lua_State *L) {
 643   if (!lua_isuserdata(L, 1)) return 0;
 644
 645   lua_getfenv(L, 1);
 646   if (lua_istable(L, -1)) {
 647     lua_getfield(L, -1, "__gc");
 648     if (lua_isfunction(L, -1)) {
 649       //cout << "found fenv gc " << lua_topointer(L, -1) << endl;
 650       lua_pushvalue(L, 1);
 651       lua_call(L, 1, 0);
 652     } else {
 653       //cout << "NOT found fenv gc" << endl;
 654       lua_pop(L, 1);
 655     }
 656   }
 657   lua_pop(L, 1);
 658
 659   // FIXME: this is useless, isn't it?
 660   void **p = static_cast<void**>(lua_touserdata(L, 1));
 661   *p = 0;
 662
 663   return 0;
 664 }
 665
 666