I would like to be able to receive the file's checksum directly from the disk via the data card

[igorkll]

A good opportunity for a data card would be to calculate the file checksum directly from disk, bypassing RAM. that is, something like this: component.data.sha256FromFilesystem(address, path). in this case, the data card itself would read the file and output the result. this will avoid reading the entire file into RAM, which may not be enough to read the entire file.

[Adrian Siekierka]

This would hurt separation of responsibilities, IMO. A better idea would be to have a callback-based checksum implementation (init/update/final).