use {SeedableRng, RngCore, u64_from_sl};
#[derive(Debug, Clone, Copy)]
pub struct Xoroshiro128Rng {
state: [u64; 2]
}
impl Xoroshiro128Rng {
#[cfg(feature = "rand")]
pub fn new() -> Self {
use rand::Rng;
let seed = rand::rngs::OsRng.gen::<<Self as SeedableRng>::Seed>();
Self::from_seed(seed)
}
pub fn new_unseeded() -> Self {
Xoroshiro128Rng::from_seed_u64([
0x193a6754a8a7d469,
0x97830e05113ba7bb
])
}
pub fn from_seed_u64(seed: [u64; 2]) -> Self {
assert!(seed != [0; 2], "Invalid seed: seed must not be 0.");
Xoroshiro128Rng { state: seed }
}
}
impl RngCore for Xoroshiro128Rng {
fn next_u32(&mut self) -> u32 {
self.next_u64() as u32
}
fn next_u64(&mut self) -> u64 {
let s0: u64 = self.state[0];
let mut s1: u64 = self.state[1];
let result: u64 = s0.wrapping_add(s1);
s1 ^= s0;
self.state[0] = s0.rotate_left(55) ^ s1 ^ (s1 << 14); self.state[1] = s1.rotate_left(36);
result
}
fn fill_bytes(&mut self, dest: &mut [u8]) {
let mut ctr = 0;
let mut v = 0;
for d in dest.iter_mut() {
if ctr == 0 {
v = self.next_u64();
ctr = 7;
}
*d = v as u8;
v >>= 8;
ctr -= 1;
}
}
fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand_core::Error> {
self.fill_bytes(dest);
Ok(())
}
}
impl SeedableRng for Xoroshiro128Rng {
type Seed = [u8; 16];
fn from_seed(seed: [u8; 16]) -> Self {
Self::from_seed_u64([u64_from_sl(&seed[..]), u64_from_sl(&seed[8..])])
}
}