Suggestion for a "Custom" File-type

Hello, i've been wondering about this for quite a few years. I used the feature extensively in Dopus 3.0, 4.0 and 5.0, 5.1 and 5.5

It was the possibility to define a custom file type irregardless of the 3-letter extension (on amiga there wasnt any such requirement).

Anyways, i remember how i could define a JPEG file type, by some JFIF header that needed to be present, and then jump to a specified byte delta, and then back and so on, to completely verify that it was a valid file-type.

The argument goes for many other file types, that has inadvertedly been named / typed incorrectly, or viruses, or any other kind of thing that wants to hinder execution or access by the wrong program (e.g. avoiding overflows).

As far as i know, its not currently possible to do this trick anymore. I know that in some cases will use a lot more cpu and a lot more reading of the hd, than a regular 3-letter recognition and linking to a specific file type, but at least i still think it would be a very nice and nifty feature, though, i dont know the reasoning for removing/(not implementing) this feature in the windows versions.

Thank you for any inputs :slight_smile:

Best regards : Jacob Eskildsen

For performance reasons and because it's unnecessary, basically. The Amiga didn't have a well-defined file extension system and so data-based recognition was needed. File extensions in Windows are well defined and understood so we decided at the start that data-based recognition wasn't needed (we did actually have a simple data-based system originally and found that it did degrade performance significantly.)

Incidentally, Opus already does do some data-based recognition - eg, rename a JPEG file to remove the suffix and then open the viewer pane, and Opus will still be able to display it.

This little utility works well from an opus button - it will identify most files with either incorrect or missing extensions: