Class DOSDisk
In: lib/DOSDisk.rb
Parent: DSK
DOSDisk DSK dot/f_4.png 
 Disk image with a standard Apple DOS 3.3 VTOC at track $11, sector $00

VTOC : Volume Table of Contents (from Beneath Apple DOS pp 4-2 & 4-3) 

 00    not used
 01    track number of first catalog sector
 02    sector number of first catalog sector
 03    release number of DOS used to INIT this disk
 04-05 not used
 06    Diskette volume number (1-254)
 07-26 not used
 27    maximum number of track/sector pairs which will fit in one file track/sector
       list sector (122 for 256 byte sectors)
 28-2F not used
 30    last track where sectors were allocated
 31    direction of track allocation (+1 or -1)
 32-33 not used
 34    number of tracks per diskette (normally 35)
 35    number of sectors per track (13 or 16)
 36-37 number of bytes per sector (LO/HI format)
 38-3B bit map of free sectors in track 0
 3C-3F bit map of free sectors in track 1
 40-43 bit map of free sectors in track 2
       ...
 BC-BF bit map of free sectors in track 33
 CO-C3 bit map of free sectors in track 34
 C4-FF bit maps for additional tracks if there are more than 35 tracks per diskette

CATALOG (from Beneath Apple DOS p 4-6) 

 00    Not Used
 01    track number of next catalog sector
 02    sector number of next catalog sector
 03-0A not used
 0B-2D First file descriptive entry
 2E-50 Second file descriptive entry
 51-73 Third file descriptive entry
 74-96 Fourth file descriptive entry
 97-B9 Fifth file descriptive entry
 BA-DC Sixth file descriptive entry
 DD-FF Seventh file descriptive entry

FILE DESCRIPTIVE ENTRY (from Beneath Apple DOS p 4-6) 

 00    Track of first track/sector list sector, if this is a deleted file this contains FF
       and the original track number is copied to the last byte of the file name (BYTE 20)
       If this byte contains a 00, the entry is assumed to never have been used and is
       available for use. (This means track 0 can never be used for data even if the DOS image
       is 'wiped' from the disk)

 01    Sector of first track/sector list sector
 02    File type and flags:
       80+file type - file is locked
       00+file type - file is not locked

       00 - TEXT file
       01 - INTEGER BASIC file
       02 - APPLESOFT BASIC file
       04 - BINARY file
       08 - S type file
       10 - RELOCATABLE object module file
       20 - a type file
       40 - b type file

 03-20 File Name (30 characters)
 21-22 Length of file in sectors (LO/HI format)

TRACK/SECTOR LIST FORMAT (from Beneath Apple DOS p 4-6) 

 00    Not used
 01    Track number of next T/S list of one is needed or zero if no more t/s list
 02    Sector number of next T/S list (if one is present)
 03-04 Not used
 05-06 Sector offset in file of the first sector described by this list
 07-oB Not used
 0C-0D Track and sector of first data sector or zeros
 0E-0F Track and sector of second data sector or zeros
 10-FF Up to 120 more track and sector pairs

Methods

add_file   delete_file   dump_catalog   file_system   find_catalog_slot   free_sector_list   get_track_sector_list   make_file   new   read_vtoc   set_sector  

Attributes

vtoc_sector_no  [RW] 
vtoc_track_no  [RW] 

Public Class methods

Public Instance methods

find_catalog_slot(filename)

iterate through the CATALOG to find either the named file or (if nil is passed in) an empty slot

free_sector_list()

iterate through the sector usage bitmap, return a list of [track,sector] for sectors marked available

get_track_sector_list(ts_list_track_no,ts_list_sector_no)

given a track and sector, treat it as a track/sector list and return an array containing track/sector pairs

make_file(filename,contents,file_options={})

default file type is TextFile Tokenisation not currently implemented

read_vtoc()

reads the VTOC, and populate the "files" array with files

[Validate]