Hashing without relying on Qt?

[Richard Kimberly Heck]

On 10/16/21 17:15, Thibaut Cuvelier wrote:
> Dear list,
>
> In my last patch (21366155), I added a dependency from InsetText to Qt 
> to be able to generate SHA hashes. The main goal is to have an 
> almost-collision-free name-generation technique, which is a great 
> useability enhancement, that's why I already pushed the patch. 
> Collisions would be awful, because two different insets would have the 
> same file name.
>
> I don't think Bernstein's hash (in Author.cpp) would fit the bill: it 
> doesn't go to great lengths to avoid collisions (it has a lot for 
> strings: 
> https://softwareengineering.stackexchange.com/questions/49550/which-hashing-algorithm-is-best-for-uniqueness-and-speed).
>
> UUID/GUID are mostly time-based or use cryptographic hash functions: 
> they do not really depend on the content, but mostly on time, and I 
> need that the file names remain constant in time (unless the LaTeX 
> code that is compiled gets changed).
>
> CityHash would be enough, but that's another dependency to add to LyX 
> (https://github.com/google/cityhash).
>
> The only solution I found without importing a large new dependency 
> into LyX was to use Qt's QCryptographicHash, just like 
> support/FileName.cpp. I know that LyX tries to have clear boundaries 
> for dependencies, that's why I'm bringing the question to the list. Is 
> the current solution acceptable? Maybe move some of the code to 
> support/FileName.cpp?

Basically, the rule is to keep Qt dependencies that aren't in the 
frontend in support. Just put some wrapper function in there, and 
that'll be fine. Maybe in support/filetools?

Riki