Initial structure

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "beacon"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "beacon"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

src/lib.rs

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+//! A Semaphore-like structure.
+
+use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::Ordering;
+use std::sync::Condvar;
+use std::sync::Mutex;
+
+pub struct Beacon {
+    lock: Mutex<AtomicUsize>,
+    guard: Condvar,
+}
+
+impl Beacon {
+    pub fn new(leases: usize) -> Self {
+        Self {
+            lock: Mutex::new(AtomicUsize::new(leases)),
+            guard: Condvar::new(),
+        }
+    }
+
+    pub fn acquire(&self, leases: usize) {
+        let mut control = self.lock.lock().unwrap();
+        let mut current_leases = control.load(Ordering::Relaxed);
+        while current_leases < leases {
+            control = self.guard.wait(control).unwrap();
+            current_leases = control.load(Ordering::Relaxed);
+        }
+
+        control.fetch_sub(leases, Ordering::SeqCst);
+    }
+
+    pub fn release(&self, leases: usize) {
+        let control = self.lock.lock().unwrap();
+        control.fetch_add(leases, Ordering::SeqCst);
+        self.guard.notify_all();
+    }
+}