Le 08/11/2022 à 23:06, Thibaut Cuvelier a écrit :
Probably, the less fancy option is to use std::hash, available since C++11. I have no idea about the quality of the produced hashes, and it seems it might really depend on the compiler too.
This seems hazardous.
I can totally understand the need for very unique hashes in this case (unlike hash tables). If you want something with unicity guarantees, the only meaningful choice is cryptographic hashes: other functions do not have the right properties (easy to compute, but no real guarantee with small hashes). Something like BLAKE2/3 should be good, performance-wise, and it's available in Qt since Qt 6 (https://doc.qt.io/qt-6/qcryptographichash.html#Algorithm-enum <https://doc.qt.io/qt-6/qcryptographichash.html#Algorithm-enum>); otherwise, Keccak since 5.9; or SHA-3 before.
Would SHA1 work? I do not care that it has been proven fragile, I do not have an opponent here. At least it also exists in Qt5 (along with md4 and md5, which re not usable if I understand).
Otherwise, you might consider using several hashes (concatenating them): I think it should provide enough entropy to have a very low probability of collision, but the hash algorithms must be really different for this to be worthwhile. (Just starting with std::hash and the string length, then see if more is required?)
Yes, but how do I see that more is required ? Because I have a bug report that some particular document is not rendered correctly? I'd rather avoid that.
JMarc -- lyx-devel mailing list [email protected] http://lists.lyx.org/mailman/listinfo/lyx-devel
