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) 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_value(), "revision overflow"); | |
Revision::from(v) | |
} | |
} |