$ git clone https://github.com/paolostivanin/libcotp.git
$ cd libcotp
$ mkdir build && cd $_
$ cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr ../   # add -DBUILD_TESTING=ON if you want to compile also the tests
$ make
# make install

char *totp = get_totp ('secretkey', digits, algo);
free (totp);

char *hotp = get_hotp ('secretkey', counter, digits, algo);
free (hotp);

int is_valid = totp_verify ('secretkey', digits, 'totp', algo); // returns either TOTP_VALID or TOTP_NOT_VALID

int is_valid = hotp_verify ('secretkey', counter, digits, 'hotp', algo); // returns either HOTP_VALID or HOTP_NOT_VALID