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The Datafile PD-CD 5
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!DiscEdit
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1995-10-20
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Disc Sector Editor © Chris Poole, 1995
--------------------------------------
Note: This documentation was rather hurriedly put together. I
will write some more complete documentation when I have time, but
in the mean time, email cep20@cam.ac.uk with any questions. More
contact details are in the licence file.
0. Licence and Disclaimer
-------------------------
This program is SHAREWARE, it is NOT public domain. You are
permitted to use it for a period of one month, after which time
you must register the software, as described below.
You may freely distribute this unregistered version as long as no
charge other than the cost of the distribution media is made. It
may be distributed by any means, including floppy disc, CD-ROM,
Internet FTP, E-mail, and through a Bulletin Board.
The software is copyright Chris Poole, 1995 and must only be
distributed unaltered, and complete with all the accompanying
documentation.
For registration details, please see the licence file.
This software is supplied 'as is', with no guarantee of its
suitablity for any purpose. The author cannot accept resposibility
for any loss or damage caused by the use, or mis-use, of this
software or its documentation.
1. Selecting a disc
-------------------
Editing a particuar filing system and drive
-------------------------------------------
Clicking on the icon bar, shows the filing system select
window. All the FileCore based filing systems are shown in the
left-hand list, the drives for the current filing system are shown
to the right. Any drives present but unreadable are shown greyed
out. The Re-read button will update the list, if discs are inserted,
etc.
Having selected a filing system and drive, clicking the OK
button will open the main disc editor window. If the drive cannot be
read, an error is reported.
!DiscEdit can edit all FileCore discs, old or new format, but
many utilities are only available for new map discs. A warning
message will be displayed if an old-map disc is edited.
Starting editing at a particular file
-------------------------------------
If a file or directory is dragged to the !DiscEdit icon, or to the
disc editor window if open, the program will attempt to locate the
file and open the main editor window at that location.
If the file is zero bytes long, or it is in an Image filing system
(such as ArcFS, SparkFS, DosFS) a warning will be displayed and the editor
window will be opened at the first sector.
If the file is dragged from a non-FileCore filing system (such as
Resources:), an error is reported and the editor window is not
opened.
ZapRedraw support
-----------------
The disc editor software will make use of the ZapRedraw
module supplied with the FreeWare editor !Zap to speed up the
redraw of the main editor window. !DiscEdit will attempt to load
the module if !Zap has been seen by the filer.
If you do not have a copy of !Zap, the editing window will re-
draw more slowly.
2. Disc Editor Operations
-------------------------
Moving around the disc
----------------------
The tool bar at the top of the window is used to navigate around
the disc.
The chunk icons step through the disc by allocated chunk.
Chunks can contain single files or directories, or they may contain a
directory and a number of files − they are the basic unit of space
allocated from the disc map. The ID icon shows the chunk ID for
the current sector. It may show '*Free*' if the chunk is free space, or
'*NoMap*' if the you are editing an old-format disc.
The sector icons step through by individual sectors − the
current disc address is shown below the icons. The 'Follow ID'
button forces !DiscEdit to follow a fragmented file when the sector
icons are used. If 'Follow ID' is not selected, the sector icons move
forward and backward through the disc from beginning to end.
When 'Follow ID' is used, the editor is constrained to the individual
chunk currently being edited. If the chunk is fragmented into more
than one area, the editor will automatically move to the next section
if the sector forward icon is clicked at the end of the first.
The data in the selected sector can be edited in hex or ASCII by
clicking to place the cursor at the appropriate point, and typing over
the data. The arrow keys can be used to move around the sector and
pressing TAB will switch between hex and ASCII editing. To re-
write the sector, use the 'Update' icon. To discard the edited sector,
use the 'Re-read' icon.
File type icon
--------------
The recessed icon on the tool bar shows !DiscEdit's guess
at the file type for the current sector, it is blank if the file type is
not known. Types can normally only be determined when the editor is
positioned at the start of the file in question. The following file types
are currently identified by !DiscEdit.
10B Symphony 3C1 TwEffect 3D6 StrHelp
3FB ArcFSArc 406 Accounts 695 GIF
AE7 ARMovie AE9 Alarms AED SheetMc
AEF Sheet AF1 Maestro AFF DrawFile
BC5 ImpDoc BCF TbleMate BD5 Envelope
BD6 AudioWrk BD7 HyprDict BE9 SWorkSp
C00 Rhapsody C0C SMacro C26 ASheet
C4B CmprDraw C55 DrumSeq C6A smArt
C7F Titler C85 JPEG CC3 Poster
CDD Ovation D83 Ignore D84 UserDict
D8E ABIDefs D94 ArtWork FAE Resource
FB1 Wave FB2 AVI FC8 DOSDisc
FCA Squash FCF Cache FD4 MIDI
FEA Desktop FF0 TIFF FF5 PoScript
FF6 Font FF8 Absolute (AIF) FF9 Sprite
FFB BASIC FFD Data (AOF)
More types will be implemented if I can find example files -
the Acorn User CD-ROM was very helpful in implementing the current
selection.
Menu functions
--------------
Clicking the menu button over the editor window opens the
menu shown below. The middle section of the menu allows you to
go to the disc map, the root directory, to any specified address, or to
a particular file ID.
At the top of the menu are utilities for map zones and
directories. These are only enabled if the editor is opened at a map
sector, or at the start of a directory.
'Calc map checksum' calculates the checksum for the currently
selected zone of the disc map. This is necessary if the zone has been
altered to prevent FileCore thinking the data is invalid. It can also
be used to repair map zones.
'Directory functions' leads to a sub-menu of operations that can
be carried out on directories. This option is only available when the
file type icon shows the current sector as a directory.
The 'Diagnostics' option performs several checks on the
integrity of the directory and reports on its findings. It is useful in
determining the cause of 'Broken Directory' errors. The checks
performed on the directory are:
· Two copies of the master sequence number agree
· Directory checksum correct
· Two copies of directory entries agree
The figure below shows an example of the output from
'Directory diagnostics' for a directory which has a corrupt entry.
You can see clearly from the list of differences between the first and
second copy of the entries that entry 1 in the first copy is corrupt.
The function has also pointed out that the checksum is incorrect,
indicating that there is something wrong.
Recommended actions are shown in the window and you would
probably now use the 'Restore from 2nd copy' option to correct the
corruption of 'Accounts95'. If the 2nd copy seems incorrect, you would
only need to correct the checksums as RISC OS only _reads_ the first
copy.
+-------------------------------------------------------------------------------+
| Directory Diagnostics |
| |
| First master sequence number: 02 |
| Second master sequence number: 02 |
| Master sequence numbers tally. |
| |
| Checksum in buffer: C7 |
| Correct checksum: C9 |
| Checksum INCORRECT - use 'Correct checksums' option. |
| |
| Second copy of directory entries disagrees |
| This may or may not cause a problem, depending on