one-time

Compute HOTP and TOTP values according to RFCs 4226 and 6238.

This implementation is digest-agnostic.

Features

All features are disabled by default.

• std: makes Error implement std::error::Error and uses std::time::SystemTime for totp_now
• libc: use libc for getting the time for totp_now

If std and libc are both enabled, libc will be used for totp_now.