I wrote up a port of GNU factor that has a slightly nicer UI than the original, and runs in approximately 1/3rd the time for 128-bit integers, on average. This is just a preliminary release and I plan implementing elliptic curve arithmetic and extending it to 192-bit to cover all the small integers that CADO-NFS doesn't support.

The factorization algorithm is provided as a separate crate that provides a C-api, since fast factorisation algorithms are hard to come-by.