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const MULTIPLIER: u128 = 2549297995355413924u128 << 64 | 4865540595714422341;
use core::fmt;
use core::mem::transmute;
use rand_core::{RngCore, SeedableRng, Error, le};
#[derive(Clone)]
#[cfg_attr(feature="serde1", derive(Serialize,Deserialize))]
pub struct Mcg128Xsl64 {
state: u128,
}
pub type Pcg64Mcg = Mcg128Xsl64;
impl Mcg128Xsl64 {
pub fn new(state: u128) -> Self {
Mcg128Xsl64 { state: state | 1 }
}
}
impl fmt::Debug for Mcg128Xsl64 {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "Mcg128Xsl64 {{}}")
}
}
impl SeedableRng for Mcg128Xsl64 {
type Seed = [u8; 16];
fn from_seed(seed: Self::Seed) -> Self {
let mut seed_u64 = [0u64; 2];
le::read_u64_into(&seed, &mut seed_u64);
let state = (seed_u64[0] as u128) |
(seed_u64[1] as u128) << 64;
Mcg128Xsl64::new(state)
}
}
impl RngCore for Mcg128Xsl64 {
#[inline]
fn next_u32(&mut self) -> u32 {
self.next_u64() as u32
}
#[inline]
fn next_u64(&mut self) -> u64 {
let state = self.state.wrapping_mul(MULTIPLIER);
self.state = state;
const XSHIFT: u32 = 64;
const ROTATE: u32 = 122;
let rot = (state >> ROTATE) as u32;
let xsl = ((state >> XSHIFT) as u64) ^ (state as u64);
xsl.rotate_right(rot)
}
#[inline]
fn fill_bytes(&mut self, dest: &mut [u8]) {
let mut left = dest;
while left.len() >= 8 {
let (l, r) = {left}.split_at_mut(8);
left = r;
let chunk: [u8; 8] = unsafe {
transmute(self.next_u64().to_le())
};
l.copy_from_slice(&chunk);
}
let n = left.len();
if n > 0 {
let chunk: [u8; 8] = unsafe {
transmute(self.next_u64().to_le())
};
left.copy_from_slice(&chunk[..n]);
}
}
#[inline]
fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
Ok(self.fill_bytes(dest))
}
}
#[cfg(test)]
mod tests {
use ::rand_core::{RngCore, SeedableRng};
use super::*;
#[test]
fn test_mcg128xsl64_construction() {
let seed = [1,2,3,4, 5,6,7,8, 9,10,11,12, 13,14,15,16];
let mut rng1 = Mcg128Xsl64::from_seed(seed);
assert_eq!(rng1.next_u64(), 7071994460355047496);
let mut rng2 = Mcg128Xsl64::from_rng(&mut rng1).unwrap();
assert_eq!(rng2.next_u64(), 12300796107712034932);
let mut rng3 = Mcg128Xsl64::seed_from_u64(0);
assert_eq!(rng3.next_u64(), 6198063878555692194);
let mut rng4 = Pcg64Mcg::seed_from_u64(0);
assert_eq!(rng4.next_u64(), 6198063878555692194);
}
#[test]
fn test_mcg128xsl64_true_values() {
let mut rng = Mcg128Xsl64::new(42);
let mut results = [0u64; 6];
for i in results.iter_mut() { *i = rng.next_u64(); }
let expected: [u64; 6] = [0x63b4a3a813ce700a, 0x382954200617ab24,
0xa7fd85ae3fe950ce, 0xd715286aa2887737, 0x60c92fee2e59f32c, 0x84c4e96beff30017];
assert_eq!(results, expected);
}
#[cfg(feature="serde1")]
#[test]
fn test_mcg128xsl64_serde() {
use bincode;
use std::io::{BufWriter, BufReader};
let mut rng = Mcg128Xsl64::seed_from_u64(0);
let buf: Vec<u8> = Vec::new();
let mut buf = BufWriter::new(buf);
bincode::serialize_into(&mut buf, &rng).expect("Could not serialize");
let buf = buf.into_inner().unwrap();
let mut read = BufReader::new(&buf[..]);
let mut deserialized: Mcg128Xsl64 = bincode::deserialize_from(&mut read).expect("Could not deserialize");
assert_eq!(rng.state, deserialized.state);
for _ in 0..16 {
assert_eq!(rng.next_u64(), deserialized.next_u64());
}
}
}