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use core::fmt;
use core::mem::transmute;
use rand_core::{RngCore, SeedableRng, Error, le, impls};
const MULTIPLIER: u64 = 6364136223846793005;
#[derive(Clone)]
#[cfg_attr(feature="serde1", derive(Serialize,Deserialize))]
pub struct Lcg64Xsh32 {
state: u64,
increment: u64,
}
pub type Pcg32 = Lcg64Xsh32;
impl Lcg64Xsh32 {
pub fn new(state: u64, stream: u64) -> Self {
let increment = (stream << 1) | 1;
Lcg64Xsh32::from_state_incr(state, increment)
}
#[inline]
fn from_state_incr(state: u64, increment: u64) -> Self {
let mut pcg = Lcg64Xsh32 { state, increment };
pcg.state = pcg.state.wrapping_add(pcg.increment);
pcg.step();
pcg
}
#[inline]
fn step(&mut self) {
self.state = self.state
.wrapping_mul(MULTIPLIER)
.wrapping_add(self.increment);
}
}
impl fmt::Debug for Lcg64Xsh32 {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "Lcg64Xsh32 {{}}")
}
}
impl SeedableRng for Lcg64Xsh32 {
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);
Lcg64Xsh32::from_state_incr(seed_u64[0], seed_u64[1] | 1)
}
}
impl RngCore for Lcg64Xsh32 {
#[inline]
fn next_u32(&mut self) -> u32 {
let state = self.state;
self.step();
const ROTATE: u32 = 59;
const XSHIFT: u32 = 18;
const SPARE: u32 = 27;
let rot = (state >> ROTATE) as u32;
let xsh = (((state >> XSHIFT) ^ state) >> SPARE) as u32;
xsh.rotate_right(rot)
}
#[inline]
fn next_u64(&mut self) -> u64 {
impls::next_u64_via_u32(self)
}
#[inline]
fn fill_bytes(&mut self, dest: &mut [u8]) {
let mut left = dest;
while left.len() >= 4 {
let (l, r) = {left}.split_at_mut(4);
left = r;
let chunk: [u8; 4] = unsafe {
transmute(self.next_u32().to_le())
};
l.copy_from_slice(&chunk);
}
let n = left.len();
if n > 0 {
let chunk: [u8; 4] = unsafe {
transmute(self.next_u32().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_lcg64xsh32_construction() {
let seed = [1,2,3,4, 5,6,7,8, 9,10,11,12, 13,14,15,16];
let mut rng1 = Lcg64Xsh32::from_seed(seed);
assert_eq!(rng1.next_u64(), 1204678643940597513);
let mut rng2 = Lcg64Xsh32::from_rng(&mut rng1).unwrap();
assert_eq!(rng2.next_u64(), 12384929573776311845);
let mut rng3 = Lcg64Xsh32::seed_from_u64(0);
assert_eq!(rng3.next_u64(), 18195738587432868099);
let mut rng4 = Pcg32::seed_from_u64(0);
assert_eq!(rng4.next_u64(), 18195738587432868099);
}
#[test]
fn test_lcg64xsh32_true_values() {
let mut rng = Lcg64Xsh32::new(42, 54);
let mut results = [0u32; 6];
for i in results.iter_mut() { *i = rng.next_u32(); }
let expected: [u32; 6] = [0xa15c02b7, 0x7b47f409, 0xba1d3330,
0x83d2f293, 0xbfa4784b, 0xcbed606e];
assert_eq!(results, expected);
}
#[cfg(feature="serde1")]
#[test]
fn test_lcg64xsh32_serde() {
use bincode;
use std::io::{BufWriter, BufReader};
let mut rng = Lcg64Xsh32::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: Lcg64Xsh32 = 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());
}
}
}