30 January 2005, 10:27 | #1 |
Posts: n/a
|
Question about IPF images of self-modifying games
Hi all,
I have the CAPS .ipf image of a game called "Moebius - The Orb of Celestial Harmony". This is a game that saves the state of your character to the original game disk. How is this accomplished? I noticed that in my \WinUAE\SaveImages directory, there is a file called Moebius_save.adf, that is created whenever the "Write Protected" box is checked with the .ipf image mounted, and deleted whenever the .ipf image is ejected. Also, the original .ipf file never seems to be modified, regardless of the state of the "Write Protected" check box. What exactly is happening with these images? The Moebius_save.adf file doesn't seem to be a normal .adf file either. It is much larger than normal disk images (about 2 megabytes), and also is not bootable, whereas the original .ipf file is. Can anyone shed some light on this mystery for me? Thanks a lot! |
30 January 2005, 11:36 | #2 |
Senior Member
Join Date: Jun 2001
Location: Germany
Posts: 1,667
|
IPF files are always write-protected, there's not way for the emulator to modify them. If a game tries to modify a disk in such a case, WinUAE will create an Extended ADF (that's a MFM disk image) and all modifications are stored there instead.
|
30 January 2005, 11:52 | #3 |
Posts: n/a
|
Hi, thanks for the reply.
So, when I play Moebius from a previously saved game, how does the emulator know when to read from the .ipf file and when to read from the MFM .adf file? It must use a combination of the two, because the game seems to always successfully get past the disk-based copy protection, but it also reads the save game properly. Thanks again! |
30 January 2005, 13:04 | #4 | |
Senior Member
Join Date: Jun 2001
Location: Germany
Posts: 1,667
|
Quote:
|
|
30 January 2005, 18:52 | #5 |
Moderator
Join Date: Jan 2003
Location: ...
Age: 52
Posts: 1,838
|
Wk is correct.
If you want more details just read the api documentation and the part about how to deal with saved/modified disk data. |
30 January 2005, 19:55 | #6 |
Posts: n/a
|
Hi everyone,
Thanks a lot for explaining this to me. It makes perfect sense and is extremely elegant. However, the use of the difference file under WinUAE seems to be keyed by filename only, so that if I am running FunGame.ipf and write-enable it, a difference file called FunGame_save.adf will be written. If I then go to a different directory containing a different game that happens to be named FunGame.ipf, it seems as though it will attempt to open and use the FunGame_save.adf difference file written for the first game. Is this correct? If so, while the chances of this happening are quite small, there is potential for such a "collision", no? Unless there is some sort of universally unique identifier associated with every .ipf image. In that case, I assume that after the first FunGame_save.adf was written, once the second FunGame.ipf was inserted, the application would create something like FunGame_save01.adf. Anyway, thanks for taking the time to help me understand this better. |
30 January 2005, 19:59 | #7 |
Moderator
Join Date: Jan 2003
Location: ...
Age: 52
Posts: 1,838
|
Yes, ipf files have an ID, disk id and revision number embedded.
Whether this is checked by uae or not for save images I can't tell. |
30 January 2005, 21:50 | #8 |
Posts: n/a
|
Very interesting. Thanks for all the information!
|
31 January 2005, 08:17 | #9 |
WinUAE developer
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 49
Posts: 26,602
|
Save images are not caps-specific. All read-only disk formats can use save-images (even zipped adf's)
Caps id can be added easily but unfortunately it would make old save images "incompatible"... |
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
Thread Tools | |
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Turbo Floppy Speed and IPF images = slow? | hipoonios | support.WinUAE | 2 | 05 September 2012 09:41 |
Using .IPF images on a real amiga | Phiber | project.SPS (was CAPS) | 46 | 18 March 2012 21:33 |
Windows icons for adf dms and ipf disk images | Galaxy | support.WinUAE | 50 | 02 March 2007 08:53 |
Using WHDLoad with IPF images | zarch | project.WHDLoad | 9 | 16 May 2006 19:29 |
Sued for modifying games | girv | project.WHDLoad | 14 | 11 February 2005 10:18 |
|
|