82 lines
2.1 KiB
Rust
82 lines
2.1 KiB
Rust
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/// 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>(seed: &[u8], mut list: Vec<T>) -> Result<Vec<T>, ShuffleErr> {
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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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if list.is_empty() {
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return Ok(list);
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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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extern crate yaml_rust;
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use self::yaml_rust::yaml;
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use std::{fs::File, io::prelude::*, path::PathBuf};
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use super::{hashing::hash, *};
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#[test]
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fn test_shuffling() {
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let mut file = {
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let mut file_path_buf = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
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file_path_buf.push("src/specs/shuffle_test_vectors.yaml");
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File::open(file_path_buf).unwrap()
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};
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let mut yaml_str = String::new();
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file.read_to_string(&mut yaml_str).unwrap();
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let docs = yaml::YamlLoader::load_from_str(&yaml_str).unwrap();
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let doc = &docs[0];
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let test_cases = doc["test_cases"].as_vec().unwrap();
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for test_case in test_cases {
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let input = test_case["input"].clone().into_vec().unwrap();
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let output = test_case["output"].clone().into_vec().unwrap();
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let seed_bytes = test_case["seed"].as_str().unwrap().as_bytes();
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let seed = if seed_bytes.len() > 0 {
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hash(seed_bytes)
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} else {
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vec![]
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};
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assert_eq!(shuffle(&seed, input).unwrap(), output);
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}
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}
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}
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