OPENSSL_store_u16_be
pos = OPENSSL_store_u16_be(pos, (uint16_t)p8fmt->p8_magic);
pos = OPENSSL_store_u16_be(pos, p8fmt->seed_magic);
pos = OPENSSL_store_u16_be(pos, (uint16_t)p8fmt->p8_magic);
pos = OPENSSL_store_u16_be(pos, p8fmt->seed_magic);
restout = OPENSSL_store_u16_be(out, u16);