Save and load: gettsl

       Name: gettsl                                                  [Show more]
       Type: Subroutine
   Category: Save and load
    Summary: Read a file's track/sector list
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * LoadFile calls gettsl


 For a detailed look at how DOS works, see the book "Beneath Apple DOS" by Don
 Worth and Pieter Lechner. In particular, see chapter 4 for the layout of the
 VTOC, catalog sector, file entry and file/track list.


 Arguments:

   buffer               The catalog sector for this file

   Y                    The offset within the catalog sector for the relevant
                        file entry


 Returns:

   buffer               The track/sector list for the file

   track                The track number of the file's data

   sector               The sector number of the file's data


.gettsl

 LDA buffer,Y           ; Set track to the track containing the track/sector
 STA track              ; list

 LDA buffer+1,Y         ; Set sector to the sector containing the track/sector
 STA sector             ; list

 JSR rsect              ; Read the track/sector list into the buffer

 LDY #$C                ; Set Y to offset $C, so it points to the track and
                        ; sector of first data sector in the track/sector list
                        ; we just loaded

 LDA buffer,Y           ; Set track to the track containing the file data
 STA track

 LDA buffer+1,Y         ; Set sector to the sector containing the file data
 STA sector

 RTS                    ; Return from the subroutine