FastDMSamplingBase::value_t FastDMSamplingInvNorm::rand(rngeng_t& rngeng)
{
std::uniform_real_distribution<double> unif_dist;
while (true) {
const value_t t = randin(rngeng, invabsmu_, invmu2_);
const value_t one2t = 0.5 / t;
if (t < 2.5) {
// short-time series
if (acceptt(t, exp(-one2t) * unif_dist(rngeng), one2t)) return t;
} else {
// long-time series
constexpr value_t Cl = -0.6773740579341821; // -log(pi/4)-log(2pi)/2;
if (acceptt(t, exp(Cl - one2t - 3 / 2 * log(t)) * unif_dist(rngeng),
PI * PI * t / 8)) return t;
}
}
}
void keygen (const char* keyfile)
{
umask(0077); // make sure key file is protected
std::ofstream keyout(keyfile);
if (!keyout) {
perror(keyfile);
std::exit(1);
}
std::ifstream randin("/dev/random");
if (!randin) {
perror("/dev/random");
std::exit(1);
}
char buffer[AES_KEY_BITS/8 + HMAC_KEY_LEN];
randin.read(buffer, sizeof(buffer));
if (randin.gcount() != sizeof(buffer)) {
std::clog << "Premature end of random data.\n";
std::exit(1);
}
keyout.write(buffer, sizeof(buffer));
}
