blob: 7f4c333fb1995436d05575fefd8995a4e8632510 [file] [log] [blame]
use std::num::NonZeroU32;
use std::sync::atomic::{AtomicU32, Ordering};
/// Value of the initial revision, as a u32. We don't use 0
/// because we want to use a `NonZeroU32`.
const START: u32 = 1;
/// A unique identifier for the current version of the database; each
/// time an input is changed, the revision number is incremented.
/// `Revision` is used internally to track which values may need to be
/// recomputed, but is not something you should have to interact with
/// directly as a user of salsa.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct Revision {
generation: NonZeroU32,
}
impl Revision {
pub(crate) fn start() -> Self {
Self::from(START)
}
pub(crate) fn from(g: u32) -> Self {
Self { generation: NonZeroU32::new(g).unwrap() }
}
pub(crate) fn next(self) -> Revision {
Self::from(self.generation.get() + 1)
}
fn as_u32(self) -> u32 {
self.generation.get()
}
}
impl std::fmt::Debug for Revision {
fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(fmt, "R{}", self.generation)
}
}
#[derive(Debug)]
pub(crate) struct AtomicRevision {
data: AtomicU32,
}
impl AtomicRevision {
pub(crate) const fn start() -> Self {
Self { data: AtomicU32::new(START) }
}
pub(crate) fn load(&self) -> Revision {
Revision::from(self.data.load(Ordering::SeqCst))
}
pub(crate) fn store(&self, r: Revision) {
self.data.store(r.as_u32(), Ordering::SeqCst);
}
/// Increment by 1, returning previous value.
pub(crate) fn fetch_then_increment(&self) -> Revision {
let v = self.data.fetch_add(1, Ordering::SeqCst);
assert!(v != u32::MAX, "revision overflow");
Revision::from(v)
}
}