461 Fried FAT Assignment

Here's the deal: you have some important data stored on a floppy disk but the darned thing is corrupted and now you can't get at it. You really can't face re-creating the data so you want to try and see how much of the file you can recover. You intend to do this by reading the entire disk into a file (binary, of course), and then trying to reconstruct your file.

So far, we have managed to dump the contents of the disk into a file. Now we have to do the rest.

The Disk Info:

Here's what we know: [ using values for single-sided ]

Floppies have: 80 tracks / side; 9 sectors / track; 512 bytes / sector

= (80 X 9 X 2) = 1440 sectors total
1440 sectors X 512 bytes = 737,280 bytes total
737,280 bytes total; a minimum of 720,000 bytes are available for index information and user space
= 17,280 bytes are available for formatting and in-sector information
= 12 bytes/sector can be reserved for formatting and locating information

The typical Floppy disk addressing works like this: [ you may or may not need this information]

Head#	Track#	Sector#	Logical Sector#
0	0	1	0
0	0	2	1
:	:	:	:
0	0	9	8
1	0	1	9
1	0	2	10
:	:	:	:
1	0	9	17
0	1	1	18
0	1	2	19
:	:	:	:
0	1	9	26
1	1	1	27
1	1	2	28
:	:	:	:
1	79	9	1439

The O/S IO system is to access information on the dusk using logical addresses only but the controller expects physical addresses.

Typical FAT looks like this:

Offset	Contents
0	8 byte file name
8	3 byte extension
11	attribute byte
	bit 0 = read only bit
	bit 1 = hidden file
	bit 2 = system file
	bit 3 = volume label entry (has no associated cluster)
	bit 4 = subdirectory entry
	bit 5 = archive (used by backup programs)
22	time (format: 5 bits for hour; 6 bits for minute; 5 bits for second)
24	date (format: 7 bits for year (year-1980); 4 bits for month; 6 bits for day)
26	starting cluster
28	2-word byte count

The File Info:

The file we are trying to recover is a Fixed Length Record file with the following format:

Field:	Contents	Size	Type
1	ID	4 bytes	integer	entry-sequenced so ID#s will be sequential in an uncorrupted file starting with #314
2	"name"	64	char
3	phone-number	5 bytes	10 digit BCD
4	"other info"	128	char
5	pad	3 bytes	zeros	- to get us to a word boundary
*total:*		*204 bytes*

Records will NOT be split across sectors.

You may write this code [including shell scripts, perl, etc.] in any language your TA is willing to mark.

The program may require user input to complete its job, or it may work 'alone'.

These are the characteristics of the 'disks':

Disk 1	- the file is fine (spread over the 'disk' in blocks, not necessarily in order), but the FAT is fried
Disk 2	- some blocks of the file are missing
Disk 3	- some number of data records are messed up - zero ID - bad / zero phone number - name is null
Disk 4	- 1st 128 bytes of each block are fried
Disk 5	- LAST 128 bytes of each block are fried
Disk 6	- file is OK but all the ID numbers are shifted
Disk 7	- the entire contents of the file is shifted by one byte

Requirements:

C- Version	Able to reconstruct file on test "disk" 1
B-Version	Able to reconstruct file on test "disks" 2-5
A-Version	Able to reconstruct file on test "disks" 6-7
BONUS	1. [5-??? Points] print diagnostic information (like what went wrong? What is missing?)