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use core::mem::size_of;
use rand_core::{RngCore, BlockRngCore, CryptoRng, SeedableRng, Error, ErrorKind};
use rand_core::impls::BlockRng;
#[derive(Debug)]
pub struct ReseedingRng<R, Rsdr>(BlockRng<ReseedingCore<R, Rsdr>>)
where R: BlockRngCore + SeedableRng,
Rsdr: RngCore;
impl<R, Rsdr> ReseedingRng<R, Rsdr>
where R: BlockRngCore + SeedableRng,
Rsdr: RngCore
{
pub fn new(rng: R, threshold: u64, reseeder: Rsdr)
-> ReseedingRng<R, Rsdr>
{
assert!(threshold <= ::core::i64::MAX as u64);
let results_empty = R::Results::default();
ReseedingRng(
BlockRng {
core: ReseedingCore {
inner: rng,
reseeder: reseeder,
threshold: threshold as i64,
bytes_until_reseed: threshold as i64,
},
index: results_empty.as_ref().len(),
results: results_empty,
}
)
}
pub fn reseed(&mut self) -> Result<(), Error> {
self.0.core.reseed()
}
}
impl<R, Rsdr: RngCore> RngCore for ReseedingRng<R, Rsdr>
where R: BlockRngCore<Item = u32> + SeedableRng,
<R as BlockRngCore>::Results: AsRef<[u32]>
{
#[inline(always)]
fn next_u32(&mut self) -> u32 {
self.0.next_u32()
}
#[inline(always)]
fn next_u64(&mut self) -> u64 {
self.0.next_u64()
}
fn fill_bytes(&mut self, dest: &mut [u8]) {
self.0.fill_bytes(dest)
}
fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
self.0.try_fill_bytes(dest)
}
}
impl<R, Rsdr> CryptoRng for ReseedingRng<R, Rsdr>
where R: BlockRngCore + SeedableRng + CryptoRng,
Rsdr: RngCore + CryptoRng {}
#[derive(Debug)]
struct ReseedingCore<R, Rsdr> {
inner: R,
reseeder: Rsdr,
threshold: i64,
bytes_until_reseed: i64,
}
impl<R, Rsdr> BlockRngCore for ReseedingCore<R, Rsdr>
where R: BlockRngCore + SeedableRng,
Rsdr: RngCore
{
type Item = <R as BlockRngCore>::Item;
type Results = <R as BlockRngCore>::Results;
fn generate(&mut self, results: &mut Self::Results) {
if self.bytes_until_reseed <= 0 {
return self.reseed_and_generate(results);
}
let num_bytes = results.as_ref().len() * size_of::<Self::Item>();
self.bytes_until_reseed -= num_bytes as i64;
self.inner.generate(results);
}
}
impl<R, Rsdr> ReseedingCore<R, Rsdr>
where R: BlockRngCore + SeedableRng,
Rsdr: RngCore
{
fn reseed(&mut self) -> Result<(), Error> {
R::from_rng(&mut self.reseeder).map(|result| {
self.bytes_until_reseed = self.threshold;
self.inner = result
})
}
#[inline(never)]
fn reseed_and_generate(&mut self,
results: &mut <Self as BlockRngCore>::Results)
{
trace!("Reseeding RNG after {} generated bytes",
self.threshold - self.bytes_until_reseed);
let threshold = if let Err(e) = self.reseed() {
let delay = match e.kind {
ErrorKind::Transient => 0,
kind @ _ if kind.should_retry() => self.threshold >> 8,
_ => self.threshold,
};
warn!("Reseeding RNG delayed reseeding by {} bytes due to \
error from source: {}", delay, e);
delay
} else {
self.threshold
};
let num_bytes = results.as_ref().len() * size_of::<<R as BlockRngCore>::Item>();
self.bytes_until_reseed = threshold - num_bytes as i64;
self.inner.generate(results);
}
}
impl<R, Rsdr> CryptoRng for ReseedingCore<R, Rsdr>
where R: BlockRngCore + SeedableRng + CryptoRng,
Rsdr: RngCore + CryptoRng {}
#[cfg(test)]
mod test {
use {Rng, SeedableRng};
use prng::chacha::ChaChaCore;
use mock::StepRng;
use super::ReseedingRng;
#[test]
fn test_reseeding() {
let mut zero = StepRng::new(0, 0);
let rng = ChaChaCore::from_rng(&mut zero).unwrap();
let mut reseeding = ReseedingRng::new(rng, 32*4, zero);
let mut buf = [0u32; 32];
reseeding.fill(&mut buf);
let seq = buf;
for _ in 0..10 {
reseeding.fill(&mut buf);
assert_eq!(buf, seq);
}
}
}