1 // Copyright 2018 Developers of the Rand project. 2 // 3 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or 4 // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license 5 // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your 6 // option. This file may not be copied, modified, or distributed 7 // except according to those terms. 8 9 //! The standard RNG 10 11 use crate::{CryptoRng, Error, RngCore, SeedableRng}; 12 13 pub(crate) use rand_chacha::ChaCha12Core as Core; 14 15 use rand_chacha::ChaCha12Rng as Rng; 16 17 /// The standard RNG. The PRNG algorithm in `StdRng` is chosen to be efficient 18 /// on the current platform, to be statistically strong and unpredictable 19 /// (meaning a cryptographically secure PRNG). 20 /// 21 /// The current algorithm used is the ChaCha block cipher with 12 rounds. Please 22 /// see this relevant [rand issue] for the discussion. This may change as new 23 /// evidence of cipher security and performance becomes available. 24 /// 25 /// The algorithm is deterministic but should not be considered reproducible 26 /// due to dependence on configuration and possible replacement in future 27 /// library versions. For a secure reproducible generator, we recommend use of 28 /// the [rand_chacha] crate directly. 29 /// 30 /// [rand_chacha]: https://crates.io/crates/rand_chacha 31 /// [rand issue]: https://github.com/rust-random/rand/issues/932 32 #[cfg_attr(doc_cfg, doc(cfg(feature = "std_rng")))] 33 #[derive(Clone, Debug, PartialEq, Eq)] 34 pub struct StdRng(Rng); 35 36 impl RngCore for StdRng { 37 #[inline(always)] next_u32(&mut self) -> u3238 fn next_u32(&mut self) -> u32 { 39 self.0.next_u32() 40 } 41 42 #[inline(always)] next_u64(&mut self) -> u6443 fn next_u64(&mut self) -> u64 { 44 self.0.next_u64() 45 } 46 47 #[inline(always)] fill_bytes(&mut self, dest: &mut [u8])48 fn fill_bytes(&mut self, dest: &mut [u8]) { 49 self.0.fill_bytes(dest); 50 } 51 52 #[inline(always)] try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>53 fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> { 54 self.0.try_fill_bytes(dest) 55 } 56 } 57 58 impl SeedableRng for StdRng { 59 type Seed = <Rng as SeedableRng>::Seed; 60 61 #[inline(always)] from_seed(seed: Self::Seed) -> Self62 fn from_seed(seed: Self::Seed) -> Self { 63 StdRng(Rng::from_seed(seed)) 64 } 65 66 #[inline(always)] from_rng<R: RngCore>(rng: R) -> Result<Self, Error>67 fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> { 68 Rng::from_rng(rng).map(StdRng) 69 } 70 } 71 72 impl CryptoRng for StdRng {} 73 74 75 #[cfg(test)] 76 mod test { 77 use crate::rngs::StdRng; 78 use crate::{RngCore, SeedableRng}; 79 80 #[test] test_stdrng_construction()81 fn test_stdrng_construction() { 82 // Test value-stability of StdRng. This is expected to break any time 83 // the algorithm is changed. 84 #[rustfmt::skip] 85 let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0, 86 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; 87 88 let target = [10719222850664546238, 14064965282130556830]; 89 90 let mut rng0 = StdRng::from_seed(seed); 91 let x0 = rng0.next_u64(); 92 93 let mut rng1 = StdRng::from_rng(rng0).unwrap(); 94 let x1 = rng1.next_u64(); 95 96 assert_eq!([x0, x1], target); 97 } 98 } 99