lua 5.1 latebound functions

#if 0
LUALIB_API void (luaL_register) (lua_State *L, const char *libname,
                                const luaL_Reg *l) {
  luaI_openlib(L, libname, l, 0);
}
#else /* late bind cfunction tables to save ram needs pairs and ipairs from 5.2 */
static int latebind_func_index(lua_State *L)
{
  const luaL_Reg *llib;
  /* name @ top of stack 1(basetable;name)-1*/
  const char *name = lua_tostring(L, -1);

  lua_pushstring (L, "__latebind");/* basetable;name;__latebind;*/
  lua_rawget (L, -3);/* basetable;name;__latebind(t);*/

  luaL_argcheck(L, lua_istable(L, -3) && lua_istable(L, -1), 1,
                "__latebind table expected");
  /* (btable;name;__latebind(t)) */

  /* lookup late bound func(s), lua_objlen allows check of multiple luaL_Reg */
  for(int i = lua_objlen(L, -1); i > 0; i--) {
    lua_rawgeti (L, -1, i);/* btable;name;__lb(t);llib*/
    llib = (const luaL_Reg *) lua_touserdata (L, -1);
    lua_pop(L, 1); /* (btable;name;__lb(t);llib) -> (btable;name;__lb(t)) */

    if(!llib)
      continue;

    for (; llib->name; llib++) {
      if(!name || strcmp(name, llib->name) == 0) {
        /* don't overwrite existing keys within basetable */
        lua_pushstring(L, llib->name); /* (btable;name;__lb(t);llib->name) */
        lua_rawget(L, -4); /* (btable;name;__lb(t);btable[func]?) */

        if(lua_isnil(L, -1)) {
          /* if function is used it is added to the base table */
          lua_pop(L, 1);
          lua_pushcclosure(L, llib->func, 0); /* (btable;name;__lb(t);llib->func) */
        }

        if(!name) /* nil name binds all functions in table immediately */
          lua_setfield(L, -4, llib->name); /* (btable;name;mtable) */
        else {
          lua_pushvalue(L, -1); /* dupe closure or existing func */
          /* (btable;name;__lb(t);llib->func;llib->func) */
          lua_setfield(L, -5, llib->name); /* (btable;name;__lb(t);llib->func) */
          /* returns the closure */
          return 1;
        }
      }
    }
  }

  lua_pop(L, 2); /* (btable;name;__lb(t)) -> (btable) */
  if(!name) {
    lua_pushnil(L); /* remove metatable (btable;name;__lb(t);nil)*/
    lua_setmetatable(L, -2);
    lua_pushnil(L); /* remove __latebind table*/
    lua_setfield (L, -2, "__latebind");
  }

  return 0;
}


static int latebind_func_pairs(lua_State *L)
{
  /* basetable @ top of stack 1(basetable)-1 */
  luaL_argcheck(L, lua_istable(L, 1), 1, "table expected");
  lua_getglobal(L, "pairs"); /* function to be called / returned (btable;pairs) */

  lua_createtable(L, 0, 15); /* btable;pairs;newtable; */
  /* clone base table */
  lua_pushnil(L); /* first key */
  while(lua_next(L, 1) != 0) {
    /* (btable;pairs;ntable;k;v) */
    lua_pushvalue(L, -2); /* dupe key Stk = (..;k;v -> ..k;v;k)*/
    lua_insert(L, -2); /* Stk = (..k;k;v) */
    lua_rawset(L, 3); /* btable;pairs;ntable;k */
  }

  lua_pushnil(L); /*nil name retrieves all unbound late bound functions */
  latebind_func_index(L);/* (btable;pairs;ntable;nil) -> (btable;pairs;ntable) */

  /* (btable;pairs;ntable) */
  lua_call(L, 1, 3); /* pairs(ntable) -> (btable;iter;state;value) */

  return 3;
}


LUALIB_API void (luaL_register) (lua_State *L, const char *libname,
                                const luaL_Reg *l) {
  if(!libname)
  {
    /* if there is no libname register normally */
    luaI_openlib(L, libname, l, 0);
    return;
  }

  /* store empty table instead of passed luaL_Reg table */
  static const struct luaL_reg late_lib [] =
  {
    {NULL, NULL}
  };

  static const struct luaL_reg late_meta [] =
  {
    {"__index", latebind_func_index},
    {"__pairs", latebind_func_pairs},
    {"__call", latebind_func_index}, /* allows t("func") -- nil binds all */
    {NULL, NULL}
  };

  //libsize_storenames(L, libname, l); /* store func names */ //IN BINARY STRINGS
  luaI_openlib(L, libname, late_lib, 0); /* basetable; */

  luaL_findtable(L, -1,"__latebind", 0); /* create table if doesn't exist */
  /* basetable;__latebind(t); */
  /* save pointer to real luaL_reg */
  lua_pushlightuserdata (L, (void *) l); /*basetable;__lb(t);userdata;*/
  lua_rawseti(L, -2, lua_objlen(L, -2) + 1); /*lb(t)[n] = userdata */

  lua_pop(L, 1);/* (basetable;__latebind(t)) -> (basetable) */

  if(luaL_newmetatable(L, "META_LATEBIND"))
  {
    luaI_openlib(L, NULL, late_meta, 0); /*basetable;metatable*/
    lua_pushvalue(L, -1); /* dupe the metatable (basetable;mt;mt) */
    lua_setfield (L, -2, "__metatable"); /* metatable[__metatable] = metatable */
  }

  lua_setmetatable(L, -2); /* (basetable;mt) -> (basetable+mtable) */
  /* base table is top of stack (basetable) */
}
#endif