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 SystemTimeDuration::now()
12 .duration_since(UNIX_EPOCH)
13 .expect(msg:"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: &(TestId, TestDescAndFn)| &test.1.desc.name).collect();
24 let test_names_hash: u64 = calculate_hash(&test_names);
25 let mut rng: Rng = Rng::new(shuffle_seed, extra:test_names_hash);
26 shuffle(&mut rng, slice: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: usize 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: usize = rng.rand_range(0..slice.len() as u64) as usize;
38 slice.swap(a:0, b: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 = DefaultHasher::new();
65 t.hash(&mut s);
66 s.finish()
67}
68