Function resizebox

third-party/lua-5.5.0/src/lauxlib.c:484–500

Resize the buffer used by a box. Optimize for the common case of ** resizing to the old size. (For instance, __gc will resize the box ** to 0 even after it was closed. 'pushresult' may also resize it to a ** final size that is equal to the one set when the buffer was created.) */

** final size that is equal to the one set when the buffer was created.)
*/
static void *resizebox (lua_State *L, int idx, size_t newsize) {
  UBox *box = (UBox *)lua_touserdata(L, idx);
  if (box->bsize == newsize)  /* not changing size? */
    return box->box;  /* keep the buffer */
  else {
    void *ud;
    lua_Alloc allocf = lua_getallocf(L, &ud);
    void *temp = allocf(ud, box->box, box->bsize, newsize);
    if (l_unlikely(temp == NULL && newsize > 0)) {  /* allocation error? */
      lua_pushliteral(L, "not enough memory");
      lua_error(L);  /* raise a memory error */
    }
    box->box = temp;
    box->bsize = newsize;
    return temp;
  }
}


static int boxgc (lua_State *L) {