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https://gitlab.com/pulsechaincom/lighthouse-pulse.git
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606c32950d
- Move `delegation` from the `transition` dir into its own dir: `beacon_chain/validator_shuffling` - Rename `beacon_chain/utils/shuffling` -> `vec_shuffle`
56 lines
1.3 KiB
Rust
56 lines
1.3 KiB
Rust
/// A library for performing deterministic, pseudo-random shuffling on a vector.
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///
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/// This library is designed to confirm to the Ethereum 2.0 specification.
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extern crate hashing;
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mod rng;
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use self::rng::ShuffleRng;
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#[derive(Debug)]
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pub enum ShuffleErr {
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ExceedsListLength,
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}
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/// Performs a deterministic, in-place shuffle of a vector.
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///
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/// The final order of the shuffle is determined by successive hashes
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/// of the supplied `seed`.
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///
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/// This is a Fisher-Yates-Durtstenfeld shuffle.
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pub fn shuffle<T>(
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seed: &[u8],
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mut list: Vec<T>)
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-> Result<Vec<T>, ShuffleErr>
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{
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let mut rng = ShuffleRng::new(seed);
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if list.len() > rng.rand_max as usize {
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return Err(ShuffleErr::ExceedsListLength);
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}
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for i in 0..(list.len() - 1) {
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let n = list.len() - i;
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let j = rng.rand_range(n as u32) as usize + i;
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list.swap(i, j);
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}
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Ok(list)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use super::hashing::canonical_hash;
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#[test]
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fn test_shuffling() {
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let seed = canonical_hash(b"4kn4driuctg8");
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let list: Vec<usize> = (0..12).collect();
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let s = shuffle(&seed, list).unwrap();
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assert_eq!(
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s,
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vec![7, 3, 2, 5, 11, 9, 1, 0, 4, 6, 10, 8],
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)
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}
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}
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