4. Converting sector numbers

Since the read and write functions expect a sector number, for systems where the sectors aren't addressed by a logical sector number (e.g. CBM drives), there are 2 conversion functions. One of them converts a logical sector number to a head/track/sector triple. The other conversion function works the other way round.

    unsigned char __fastcall__ dio_phys_to_log (dhandle_t handle,
                                                const dio_phys_pos *physpos,
                                                sectnum_t *sectnum);

This function converts track/head/sector to logical sector number.

    unsigned char __fastcall__ dio_log_to_phys (dhandle_t handle,
                                                const _sectnum_t *sectnum,
                                                dio_phys_pos *physpos);

This function converts a logical sector number to track/head/sector notation.

Note, that on systems which natively use logical sector numbers (e.g. Atari), the conversion functions are dummies. They ignore head/track (dio_phys_to_log) or return them as zero (dio_log_to_phys). The logical sector number is returned as physical sector and vice versa.