sync15/client/
util.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
4
5use std::collections::{HashMap, HashSet};
6use std::sync::atomic::{AtomicU32, Ordering};
7
8/// Finds the maximum of the current value and the argument `val`, and sets the
9/// new value to the result.
10///
11/// Note: `AtomicFoo::fetch_max` is unstable, and can't really be implemented as
12/// a single atomic operation from outside the stdlib ;-;
13pub(crate) fn atomic_update_max(v: &AtomicU32, new: u32) {
14    // For loads (and the compare_exchange_weak second ordering argument) this
15    // is too strong, we could probably get away with Acquire (or maybe Relaxed
16    // because we don't need the result?). In either case, this fn isn't called
17    // from a hot spot so whatever.
18    let mut cur = v.load(Ordering::SeqCst);
19    while cur < new {
20        // we're already handling the failure case so there's no reason not to
21        // use _weak here.
22        match v.compare_exchange_weak(cur, new, Ordering::SeqCst, Ordering::SeqCst) {
23            Ok(_) => {
24                // Success.
25                break;
26            }
27            Err(new_cur) => {
28                // Interrupted, keep trying.
29                cur = new_cur
30            }
31        }
32    }
33}
34
35// Slight wrappers around the builtin methods for doing this.
36pub(crate) fn set_union(a: &HashSet<String>, b: &HashSet<String>) -> HashSet<String> {
37    a.union(b).cloned().collect()
38}
39
40pub(crate) fn set_difference(a: &HashSet<String>, b: &HashSet<String>) -> HashSet<String> {
41    a.difference(b).cloned().collect()
42}
43
44pub(crate) fn set_intersection(a: &HashSet<String>, b: &HashSet<String>) -> HashSet<String> {
45    a.intersection(b).cloned().collect()
46}
47
48pub(crate) fn partition_by_value(v: &HashMap<String, bool>) -> (HashSet<String>, HashSet<String>) {
49    let mut true_: HashSet<String> = HashSet::new();
50    let mut false_: HashSet<String> = HashSet::new();
51    for (s, val) in v {
52        if *val {
53            true_.insert(s.clone());
54        } else {
55            false_.insert(s.clone());
56        }
57    }
58    (true_, false_)
59}
60
61#[cfg(test)]
62mod test {
63    use super::*;
64
65    #[test]
66    fn test_set_ops() {
67        fn hash_set(s: &[&str]) -> HashSet<String> {
68            s.iter()
69                .copied()
70                .map(ToOwned::to_owned)
71                .collect::<HashSet<_>>()
72        }
73
74        assert_eq!(
75            set_union(&hash_set(&["a", "b", "c"]), &hash_set(&["b", "d"])),
76            hash_set(&["a", "b", "c", "d"]),
77        );
78
79        assert_eq!(
80            set_difference(&hash_set(&["a", "b", "c"]), &hash_set(&["b", "d"])),
81            hash_set(&["a", "c"]),
82        );
83        assert_eq!(
84            set_intersection(&hash_set(&["a", "b", "c"]), &hash_set(&["b", "d"])),
85            hash_set(&["b"]),
86        );
87        let m: HashMap<String, bool> = [
88            ("foo", true),
89            ("bar", true),
90            ("baz", false),
91            ("quux", false),
92        ]
93        .iter()
94        .copied()
95        .map(|(a, b)| (a.to_owned(), b))
96        .collect();
97        assert_eq!(
98            partition_by_value(&m),
99            (hash_set(&["foo", "bar"]), hash_set(&["baz", "quux"])),
100        );
101    }
102}
sync15/client/util.rs

sync15/client/
util.rs
