use cap_rand::RngCore; /// Implement `insecure-random` using a deterministic cycle of bytes. pub struct Deterministic { cycle: std::iter::Cycle>, } impl Deterministic { pub fn new(bytes: Vec) -> Self { Deterministic { cycle: bytes.into_iter().cycle(), } } } impl RngCore for Deterministic { fn next_u32(&mut self) -> u32 { let b0 = self.cycle.next().expect("infinite sequence"); let b1 = self.cycle.next().expect("infinite sequence"); let b2 = self.cycle.next().expect("infinite sequence"); let b3 = self.cycle.next().expect("infinite sequence"); ((b0 as u32) << 24) + ((b1 as u32) << 16) + ((b2 as u32) << 8) + (b3 as u32) } fn next_u64(&mut self) -> u64 { let w0 = self.next_u32(); let w1 = self.next_u32(); ((w0 as u64) << 32) + (w1 as u64) } fn fill_bytes(&mut self, buf: &mut [u8]) { for b in buf.iter_mut() { *b = self.cycle.next().expect("infinite sequence"); } } fn try_fill_bytes(&mut self, buf: &mut [u8]) -> Result<(), cap_rand::Error> { self.fill_bytes(buf); Ok(()) } } #[cfg(test)] mod test { use super::*; #[test] fn deterministic() { let mut det = Deterministic::new(vec![1, 2, 3, 4]); let mut buf = vec![0; 1024]; det.try_fill_bytes(&mut buf).expect("get randomness"); for (ix, b) in buf.iter().enumerate() { assert_eq!(*b, (ix % 4) as u8 + 1) } } } pub fn thread_rng() -> Box { use cap_rand::{Rng, SeedableRng}; let mut rng = cap_rand::thread_rng(cap_rand::ambient_authority()); Box::new(cap_rand::rngs::StdRng::from_seed(rng.gen())) }