Sha256: a7d4bb5649223a868f4d2d3072c0d36cf6f8d3ec25420267505488374dc8a775
Contents?: true
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Versions: 39
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Stored size: 1.5 KB
Contents
use cap_rand::RngCore;
/// Implement `WasiRandom` using a deterministic cycle of bytes.
pub struct Deterministic {
cycle: std::iter::Cycle<std::vec::IntoIter<u8>>,
}
impl Deterministic {
pub fn new(bytes: Vec<u8>) -> 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)
}
}
}
Version data entries
39 entries across 39 versions & 1 rubygems