ra_salsa/
revision.rs

1use std::num::NonZeroU32;
2use std::sync::atomic::{AtomicU32, Ordering};
3
4/// Value of the initial revision, as a u32. We don't use 0
5/// because we want to use a `NonZeroU32`.
6const START: u32 = 1;
7
8/// A unique identifier for the current version of the database; each
9/// time an input is changed, the revision number is incremented.
10/// `Revision` is used internally to track which values may need to be
11/// recomputed, but is not something you should have to interact with
12/// directly as a user of salsa.
13#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
14pub struct Revision {
15    generation: NonZeroU32,
16}
17
18impl Revision {
19    pub(crate) fn start() -> Self {
20        Self::from(START)
21    }
22
23    pub(crate) fn from(g: u32) -> Self {
24        Self { generation: NonZeroU32::new(g).unwrap() }
25    }
26
27    pub(crate) fn next(self) -> Revision {
28        Self::from(self.generation.get() + 1)
29    }
30
31    fn as_u32(self) -> u32 {
32        self.generation.get()
33    }
34}
35
36impl std::fmt::Debug for Revision {
37    fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
38        write!(fmt, "R{}", self.generation)
39    }
40}
41
42#[derive(Debug)]
43pub(crate) struct AtomicRevision {
44    data: AtomicU32,
45}
46
47impl AtomicRevision {
48    pub(crate) const fn start() -> Self {
49        Self { data: AtomicU32::new(START) }
50    }
51
52    pub(crate) fn load(&self) -> Revision {
53        Revision::from(self.data.load(Ordering::SeqCst))
54    }
55
56    pub(crate) fn store(&self, r: Revision) {
57        self.data.store(r.as_u32(), Ordering::SeqCst);
58    }
59
60    /// Increment by 1, returning previous value.
61    pub(crate) fn fetch_then_increment(&self) -> Revision {
62        let v = self.data.fetch_add(1, Ordering::SeqCst);
63        assert!(v != u32::MAX, "revision overflow");
64        Revision::from(v)
65    }
66}
ra_salsa/revision.rs

ra_salsa/
revision.rs
