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