Similar Functions to Informix conversion functions dectoasc() and rfmtdate()

In essence how do I do something like this in Oracle:

void Convert_date_decimal(){
 int ret_code = 0;

 if ( ret_code = dectoasc( &temp_key2, t_key2, 16, 4)){   t_key2[0] = '\0';
}

 else {
  t_key2[16] = '\0';
}

 if (ret_code = rfmtdate( temp_key3, "mm dd yyyy", t_key3)){   t_key3[0] = '\0';
}

 if ( ret_code = rfmtdate( temp_key4, "mm dd yyyy", t_key4)){   t_key4[0] = '\0';
}

}

/* end function convert_date_decimal()                  */