test/helpers/
shuffle.rs

1use std::hash::{DefaultHasher, Hasher};
2use std::time::{SystemTime, UNIX_EPOCH};
3
4use crate::cli::TestOpts;
5use crate::types::{TestDescAndFn, TestId, TestName};
6
7pub(crate) fn get_shuffle_seed(opts: &TestOpts) -> Option<u64> {
8    opts.shuffle_seed.or_else(|| {
9        if opts.shuffle {
10            Some(
11                SystemTime::now()
12                    .duration_since(UNIX_EPOCH)
13                    .expect("Failed to get system time")
14                    .as_nanos() as u64,
15            )
16        } else {
17            None
18        }
19    })
20}
21
22pub(crate) fn shuffle_tests(shuffle_seed: u64, tests: &mut [(TestId, TestDescAndFn)]) {
23    let test_names: Vec<&TestName> = tests.iter().map(|test| &test.1.desc.name).collect();
24    let test_names_hash = calculate_hash(&test_names);
25    let mut rng = Rng::new(shuffle_seed, test_names_hash);
26    shuffle(&mut rng, tests);
27}
28
29// `shuffle` is from `rust-analyzer/src/cli/analysis_stats.rs`.
30fn shuffle<T>(rng: &mut Rng, slice: &mut [T]) {
31    for i in 0..slice.len() {
32        randomize_first(rng, &mut slice[i..]);
33    }
34
35    fn randomize_first<T>(rng: &mut Rng, slice: &mut [T]) {
36        assert!(!slice.is_empty());
37        let idx = rng.rand_range(0..slice.len() as u64) as usize;
38        slice.swap(0, idx);
39    }
40}
41
42struct Rng {
43    state: u64,
44    extra: u64,
45}
46
47impl Rng {
48    fn new(seed: u64, extra: u64) -> Self {
49        Self { state: seed, extra }
50    }
51
52    fn rand_range(&mut self, range: core::ops::Range<u64>) -> u64 {
53        self.rand_u64() % (range.end - range.start) + range.start
54    }
55
56    fn rand_u64(&mut self) -> u64 {
57        self.state = calculate_hash(&(self.state, self.extra));
58        self.state
59    }
60}
61
62// `calculate_hash` is from `core/src/hash/mod.rs`.
63fn calculate_hash<T: core::hash::Hash>(t: &T) -> u64 {
64    let mut s = DefaultHasher::new();
65    t.hash(&mut s);
66    s.finish()
67}