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// Copyright 2018 Developers of the Rand project.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! The standard RNG
use crate::{RngCore, CryptoRng, Error, SeedableRng};
#[cfg(target_os = "emscripten")] pub(crate) use rand_hc::Hc128Core as Core;
#[cfg(not(target_os = "emscripten"))] pub(crate) use rand_chacha::ChaCha20Core as Core;
#[cfg(target_os = "emscripten")] use rand_hc::Hc128Rng as Rng;
#[cfg(not(target_os = "emscripten"))] use rand_chacha::ChaCha20Rng as Rng;
/// The standard RNG. The PRNG algorithm in `StdRng` is chosen to be efficient
/// on the current platform, to be statistically strong and unpredictable
/// (meaning a cryptographically secure PRNG).
///
/// The current algorithm used is the ChaCha block cipher with either 20 or 12
/// rounds (see the `stdrng_*` feature flags, documented in the README).
/// This may change as new evidence of cipher security and performance
/// becomes available.
///
/// The algorithm is deterministic but should not be considered reproducible
/// due to dependence on configuration and possible replacement in future
/// library versions. For a secure reproducible generator, we recommend use of
/// the [rand_chacha] crate directly.
///
/// [rand_chacha]: https://crates.io/crates/rand_chacha
#[derive(Clone, Debug)]
pub struct StdRng(Rng);
impl RngCore for StdRng {
#[inline(always)]
fn next_u32(&mut self) -> u32 {
self.0.next_u32()
}
#[inline(always)]
fn next_u64(&mut self) -> u64 {
self.0.next_u64()
}
#[inline(always)]
fn fill_bytes(&mut self, dest: &mut [u8]) {
self.0.fill_bytes(dest);
}
#[inline(always)]
fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
self.0.try_fill_bytes(dest)
}
}
impl SeedableRng for StdRng {
type Seed = <Rng as SeedableRng>::Seed;
#[inline(always)]
fn from_seed(seed: Self::Seed) -> Self {
StdRng(Rng::from_seed(seed))
}
#[inline(always)]
fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
Rng::from_rng(rng).map(StdRng)
}
}
impl CryptoRng for StdRng {}
#[cfg(test)]
mod test {
use crate::{RngCore, SeedableRng};
use crate::rngs::StdRng;
#[test]
fn test_stdrng_construction() {
// Test value-stability of StdRng. This is expected to break any time
// the algorithm is changed.
let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
#[cfg(any(feature="stdrng_strong", not(feature="stdrng_fast")))]
let target = [3950704604716924505, 5573172343717151650];
#[cfg(all(not(feature="stdrng_strong"), feature="stdrng_fast"))]
let target = [10719222850664546238, 14064965282130556830];
let mut rng0 = StdRng::from_seed(seed);
let x0 = rng0.next_u64();
let mut rng1 = StdRng::from_rng(rng0).unwrap();
let x1 = rng1.next_u64();
assert_eq!([x0, x1], target);
}
}
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