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 (
The logical sector number is returned as physical sector and vice versa.