lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

Title: void lua_resizetable


I have a situation where I am storing potentially 1000s of lua tables that I need to reference quickly from C. One optimal way of doing this seemed to be to put them into the array portion of the global table, that way I can use LUA_GLOBALSINDEX to easily get at those tables by a single integer lookup. But the global table doesn’t seem to have an array just a hash table, and adding to it with rawseti even with an integer index just puts the new values in the hash table.

I couldnt find a way to force the global table to have an array, so I made this function that lives in lapi.c:

LUA_API void lua_resizetable (lua_State *L, int idx, int n) {

  StkId o;


  api_checknelems(L, 1);

  o = index2adr(L, idx);

  api_check(L, ttistable(o));

  luaH_resizearray(L, hvalue(o), n);

  luaC_barriert(L, hvalue(o), L->top-1);




So I can then call:

lua_resizetable(ec.L, LUA_GLOBALSINDEX, 10000);

Now the global table has an array and I can use rawseti and rawgeti to access my tables in linear time with code like:

lua_rawgeti(ec.L, LUA_GLOBALSINDEX, m_value);

Sure, I could have used another non-global table, but then I would have to look that table up, push it on the stack at an appropriate index every time, instead of using LUA_GLOBALSINDEX which is always valid.

Is this the wrong thing to do?


Sean Riley

Lead Programmer, Metaplace.

"All problems in computer science can be solved by another level of indirection", Butler Lampson, 1972