Identify disk space for cracktro/trainer

[hop]

Are there any nice techniques for identifying space on a (cracked) non-dos game floppy disk in which to add a cracktro or trainer?

I thought I'd have a go after watching one of Hoffman's streams. Always wondered how this stuff worked. Great fun. Just done a non-dos game (Paramax with a little help from the Flashtro tutorial when it came to patching the decoded code in the loader). Thought it would be nice to try to add a little cracktro/trainer, but not sure how to identify unused space on disk.

Using a modern hex editor (HxD) I scrolled through the ADF and by eye identified a couple of regions which look like they are DOS formatted (tracks 46-59,151-159) as well as a region of zeros at the end of track 150. So I guess this is a good place to stick the extra data.

This method seems a bit bit prone to human error, and might not have been very convenient back in the day. Are there any better tried-and-tested ways other than high-speed eye-balling? Thanks for any insight.

[phx]

When you cracked the game you would usually know all about the disk layout and where any space for a cracktro is.

When you don't, then "lamers" would just use the space of the original cracktro.

[demoniac]

You could always select the empty sections with the modern hex editor and see if the total bytes would exceed your cracktro/trainer's size.

[hop]

Yes. I suppose most games has disk based protection so the disk layout would need to be redone anyway.

[Galahad/FLT]

If there was a protection track, you can use that space.

If you find "DOS" format strings that haven't been overwritten by the game then you know they at free, but really you should be able to observe the loaded tracks or at least interrogate the file list.

Or it could be there is no room, so you have to make it, is the main code compressed? If not, compress it and then you will free up space on the disk.

[Galahad/FLT]

Originally Posted by hop

Yes. I suppose most games has disk based protection so the disk layout would need to be redone anyway.

Not necessarily.

If the disk just has a protection track and normal dose tracks, there is no expectation you need to adjust the layout of the data.

Same on some games that have a custom MFM format, if the size of the disk format is the same as AmigaDOS tracks, you don't need to adjust the data, it can remain in the same place with simply a loader swap.

It's down to your experience of that protection that ultimately will decide if the disk layout changes.

One cracker might simply keep it sector loading, another cracker with the same game might crack the game to files.

[pandy71]

Perhaps: https://corte.si/posts/visualisation/entropy/index.html
straight to target: http://binvis.io/#/