2 files changed, 80 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/limit/Cargo.toml b/src/tools/rust-analyzer/crates/limit/Cargo.toml
new file mode 100644
index 000000000..893db436d
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/limit/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "limit"
+version = "0.0.0"
+description = "TBD"
+license = "MIT OR Apache-2.0"
+edition = "2021"
+rust-version = "1.57"
+
+[features]
+tracking = []
+default = ["tracking"]
diff --git a/src/tools/rust-analyzer/crates/limit/src/lib.rs b/src/tools/rust-analyzer/crates/limit/src/lib.rs
new file mode 100644
index 000000000..d6a706a7c
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/limit/src/lib.rs
@@ -0,0 +1,69 @@
+//! limit defines a struct to enforce limits.
+
+#![warn(rust_2018_idioms, unused_lifetimes, semicolon_in_expressions_from_macros)]
+
+#[cfg(feature = "tracking")]
+use std::sync::atomic::AtomicUsize;
+
+/// Represents a struct used to enforce a numerical limit.
+pub struct Limit {
+    upper_bound: usize,
+    #[cfg(feature = "tracking")]
+    max: AtomicUsize,
+}
+
+impl Limit {
+    /// Creates a new limit.
+    #[inline]
+    pub const fn new(upper_bound: usize) -> Self {
+        Self {
+            upper_bound,
+            #[cfg(feature = "tracking")]
+            max: AtomicUsize::new(0),
+        }
+    }
+
+    /// Creates a new limit.
+    #[inline]
+    #[cfg(feature = "tracking")]
+    pub const fn new_tracking(upper_bound: usize) -> Self {
+        Self {
+            upper_bound,
+            #[cfg(feature = "tracking")]
+            max: AtomicUsize::new(1),
+        }
+    }
+
+    /// Gets the underlying numeric limit.
+    #[inline]
+    pub const fn inner(&self) -> usize {
+        self.upper_bound
+    }
+
+    /// Checks whether the given value is below the limit.
+    /// Returns `Ok` when `other` is below `self`, and `Err` otherwise.
+    #[inline]
+    pub fn check(&self, other: usize) -> Result<(), ()> {
+        if other > self.upper_bound {
+            Err(())
+        } else {
+            #[cfg(feature = "tracking")]
+            loop {
+                use std::sync::atomic::Ordering;
+                let old_max = self.max.load(Ordering::Relaxed);
+                if other <= old_max || old_max == 0 {
+                    break;
+                }
+                if self
+                    .max
+                    .compare_exchange_weak(old_max, other, Ordering::Relaxed, Ordering::Relaxed)
+                    .is_ok()
+                {
+                    eprintln!("new max: {}", other);
+                }
+            }
+
+            Ok(())
+        }
+    }
+}