luaL_buffinitsize
LUALIB_API char *(luaL_buffinitsize) (lua_State *L, luaL_Buffer *B, size_t sz);
char *p = luaL_buffinitsize(L, &b, l);
char *p = luaL_buffinitsize(L, &b, l);
char *p = luaL_buffinitsize(L, &b, totallen);
char *p = luaL_buffinitsize(L, &b, n);
char *p = luaL_buffinitsize(L, &b, l);