ulSize (ULONG) - input

Size in bytes required for pBuffer.

Can be specified as 0. In this case, the function returns the size of the transform data:

ulSize=GreSaveXformData (hdc, 0, 0);     /* Find out how large the buffer must be, */
GreSaveXformData (hdc, ulSize, pBuffer); /* then save the transform state.         */