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use std::num::Wrapping as w;
use rand::{Rand, Rng, SeedableRng};
use RngJump;
const STATE_SIZE: usize = 2;
#[derive(Copy, Clone)]
pub struct Xorshift128([u64; 2]);
static EMPTY: Xorshift128 = Xorshift128([0, 0]);
static JUMP: [u64; 2] = [0x8a5cd789635d2dff, 0x121fd2155c472f96];
impl Rng for Xorshift128 {
fn next_u32(&mut self) -> u32 {
self.next_u64() as u32
}
#[inline]
fn next_u64(&mut self) -> u64 {
let mut s1 = w(self.0[0]);
let s0 = w(self.0[1]);
let result = s0 + s1;
self.0[0] = s0.0;
s1 ^= s1 << 23;
self.0[1] = (s1 ^ s0 ^ (s1 >> 18) ^ (s0 >> 5)).0;
result.0
}
}
impl<'a> SeedableRng<&'a [u64]> for Xorshift128 {
fn reseed(&mut self, seed: &'a [u64]) {
if seed.len() < 2 {
panic!("Xorshift128 seed needs at least two u64s for seeding.");
}
self.0[0] = seed[0];
self.0[1] = seed[1];
}
fn from_seed(seed: &'a [u64]) -> Xorshift128 {
let mut rng = EMPTY;
rng.reseed(seed);
rng
}
}
impl Rand for Xorshift128 {
fn rand<R: Rng>(other: &mut R) -> Xorshift128 {
let mut key: [u64; STATE_SIZE] = [0; STATE_SIZE];
for word in &mut key {
*word = other.gen();
}
SeedableRng::from_seed(&key[..])
}
}
impl RngJump for Xorshift128 {
fn jump(&mut self, count: usize) {
for _ in 0..count {
let mut s0: u64 = 0;
let mut s1: u64 = 0;
for i in &JUMP {
for b in 0..64 {
if (i & 1 << b) != 0 {
s0 ^= self.0[0];
s1 ^= self.0[1];
}
self.next_u64();
}
}
self.0[0] = s0;
self.0[1] = s1;
}
}
}
#[cfg(test)]
mod tests {
use rand::{Rng, SeedableRng};
use super::Xorshift128;
#[test]
fn test() {
let seed: u64 = 1477776990746309507;
let t_vals: Vec<u64> = vec![2955553981492619014,
4599697141668829146,
4670196263639928724,
16937752213077027105,
9891185907692497053,
15201764008617186196,
15346536721100407138,
1632066265273679815,
3374113843714423023,
16609654801952101372,
10179374700856453570,
13415587091341440,
13713531109933318529,
9635993043755786933,
13325653044572447755,
15693762250133287478,
12271064446641005509,
2709845634781129372,
12573435284135488980,
12323032091170684494,
16353258292748552418,
10233934017009620357,
14350043634790606694,
15857154722661923587,
9599170926588813820,
9313747211033478552,
7650530421537508985,
633304507529020339,
1432383473114491350,
11195010954091482555,
2197040232331856193,
17592989984699807827,
12638411464544161602,
4396142987860263564,
16456439119028401503,
1345258822949363305,
3509353510520372253,
18232499665317415612,
10679351282305608316,
9368589195308537593,
4894090245044721815,
1948558019100264117,
18309589142408570815,
4816161030343661271,
11210608633196506254,
12612051789490434918,
11585670264215608103,
946134795473836869,
9936715390587068425,
4972002347465534564];
let states = [seed, seed];
let mut rng: Xorshift128 = SeedableRng::from_seed(&states[..]);
let vals = rng.gen_iter::<u64>().take(t_vals.len()).collect::<Vec<u64>>();
assert!(::test::iter_eq(t_vals, vals));
}
}