file/directory crc

[ot-goegelem]

In order to check the integrity of file transfers or directory listings it would be nice to have a way of requesting a checksum over a file/directory in order to detect edge cases where the file/directory changes between subsequent requests.

Additionally it would also allow to do some prior checks in order to not sync any files that are already present.

To be fair the cyphal specification mentions the methodology to put "hash-files" near the real files (like image.bin.sha256) which works for "static" files, but this becomes cumbersome for files that change all the time, because someone has to update those "hash-files". Unfortunately this will also not help in the "list-directory" case as it is very hard to detect an "a file prior to the current index was deleted" error where the file that would have been at the current index prior to deletion will not show up in the listing.