mpf_checksum
if (mpf_checksum((unsigned char *)mpc, mpc->length)) {
!mpf_checksum((unsigned char *)bp, 16) &&
mpc->checksum -= mpf_checksum((unsigned char *)mpc, mpc->length);
old = mpf_checksum((unsigned char *)mpc, mpc->length);
new = mpf_checksum((unsigned char *)mpc, mpc->length);
mpf->checksum -= mpf_checksum((unsigned char *)mpf, 16);