bendns' repos / rust-analyzer
Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/ra-salsa/src/revision.rs')
-rw-r--r--crates/ra-salsa/src/revision.rs66
1 files changed, 66 insertions, 0 deletions
diff --git a/crates/ra-salsa/src/revision.rs b/crates/ra-salsa/src/revision.rs
new file mode 100644
index 0000000000..7f4c333fb1
--- /dev/null
+++ b/crates/ra-salsa/src/revision.rs
@@ -0,0 +1,66 @@
+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)
+ }
+}