Overwrite on different MD5

Hi people,

When copying files that already exist at the target, dopus asks me, if I want to overwrite, skip, overwrite all or skip all file/s. I would find it very useful if it is also possible to select somthing like "overwrite when checksum is different" or something like that. This ensures to copy also the damaged files.

Best regards
Marco Sorich

To calculate the MD5 checksum of each file you'd have to read all of the source file and all of the destination file and then still have to re-read and write the file should there be a difference.

Unless you're in a situation where the files are on a network drive and downloading is much faster than uploading, I can't see this being much faster than simply overwriting all the files.

Maybe I'm wrong and writing to harddrives is that much slower that it's faster to avoid writing by reading 2 to 3 times as much, but my gut feeling is it wouldn't be worth it.

I already saw a posting related to this earlier.
That was a request to only show the replace/skip dialog when the files were actually different. If you look at ACDSee (the image viewer, I use version 3.1 still), that functionality is there.
Even with DO I use this functionality of ACDSee to drag/drop a set of files to a directory in ACDSee and let that it find out which files are different an a dialog must appear to ask the user to overwrite/skip. The dialog is similar to the DO dialog (i.e. with preview, etc).
I would much like this functionality also in DO, so I can ditch ACDSee.

Greetz,
Martin Smits

I'd like a prefs option to show the MD5 checksum on the Replace dialog.

1 Like

That's right, this feature doesn't make sense for speeding up the transfere.

[quote]
ommos wrote:
I use this functionality of ACDSee to drag/drop a set of files to a directory in ACDSee and let that it find out which files are different an a dialog must appear to ask the user to overwrite/skip. The dialog is similar to the DO dialog (i.e. with preview, etc).
I would much like this functionality also in DO, so I can ditch ACDSee.[/quote]

I think Dopus does indeed have room for enhancement here, but keep in mind that MD5 sums are a different beast than what ACDSee is most likely calculating. If it's not just doing a name/size comparison, it's probably doing a regular (non-MD5) CRC check which if I'm not mistaken is available as file system meta-data, and not something that needs to be 'calculated'. If this were checked, where it would be much faster than calculating the MD5 checksum, then especially in the case of series of large files I think you COULD increase your overall time to transfer.

There's no CRC available from the file-system as far as I know. And even it there was you wouldn't be able to safely rely on it (standard 32-bit CRC is very insecure). Even MD5 has been shown to be insecure these days...

Hmmm... I could have sworn that I used to see a CRC values on some file properties page at one time... though it's certainly not there now and I can't for the life of me remember why I recall this.

But anyway, yes CRC is an insecure data validation method but MD5 I believe takes a lot longer to calculate... if you added an MD5 check in the copy/replace/rename dialog it would take for ever for really large files eh? Adding this sounds like it would be akin to giving us guns and bullets and asking us to please not shoot ourselves in the foot :slight_smile:. Maybe only balanced in usefullness if it adhered to the MaxHashSize value the rest of the products usage of MD5 followed (though thankfully NOT the explicit dupe files search based on md5). Or perhaps as a button in the copy/replace/rename dialog that we woud have to press to see this info on a file by file on demand basis.