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use std::fs::File;
use std::io::Read;
use std::sync::Mutex;
use std::time::SystemTime;
static STATE: Mutex<u64> = Mutex::new(0);
fn seed_urandom() -> Option<()> {
let mut f = File::open("/dev/urandom").ok()?;
let mut bytes = [0; 8];
f.read_exact(&mut bytes).ok()?;
*STATE.lock().unwrap() = u64::from_ne_bytes(bytes);
return Some(());
}
fn seed_time() -> Option<()> {
let n = SystemTime::now()
.duration_since(SystemTime::UNIX_EPOCH)
.ok()?;
*STATE.lock().unwrap() = n.as_nanos() as u64;
return Some(());
}
pub fn seed() -> Option<()> {
match seed_urandom() {
Some(()) => return Some(()),
None => (),
}
match seed_time() {
Some(()) => return Some(()),
None => (),
}
return None;
}
fn mix(s: &mut u64) {
// https://en.wikipedia.org/wiki/Linear_congruential_generator
*s = s.wrapping_mul(6364136223846793005).wrapping_add(1);
}
pub fn random() -> f64 {
let mut s = STATE.lock().unwrap();
mix(&mut s);
return (*s >> 32) as f64 / 4294967296.;
}
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