From 0579fb14ef4be4f9ccbb621758ba1d2d7235a489 Mon Sep 17 00:00:00 2001
From: Christian Cunningham <c@localhost>
Date: Fri, 26 Aug 2022 17:24:34 -0700
Subject: Add Spinlock

---
 src/sync.rs | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

(limited to 'src/sync.rs')

diff --git a/src/sync.rs b/src/sync.rs
index 0e0ace2..38cffc8 100644
--- a/src/sync.rs
+++ b/src/sync.rs
@@ -81,3 +81,59 @@ impl<T> interface::Mutex for NullLock<T> {
         f(data)
     }
 }
+
+use core::sync::atomic::{AtomicBool, Ordering};
+
+pub struct SpinLock<T>
+where
+    T: Sized,
+{
+    data: UnsafeCell<T>,
+    lock: AtomicBool,
+}
+
+unsafe impl<T> Send for SpinLock<T> where T: Sized + Send {}
+unsafe impl<T> Sync for SpinLock<T> where T: Sized + Send {}
+
+impl<T> SpinLock<T> {
+    /// # New lock
+    pub const fn new(data: T) -> Self {
+        Self {
+            data: UnsafeCell::new(data),
+            lock: AtomicBool::new(false),
+        }
+    }
+}
+
+impl<T: interface::Initializable> SpinLock<T> {
+    /// # Init
+    pub fn init(&self) {
+        use interface::Mutex;
+        self.lock(|init| {
+            init.init();
+        });
+    }
+}
+
+impl<T> interface::Mutex for SpinLock<T> {
+    /// # Data type
+    type Data = T;
+    /// # Lock
+    fn lock<'a, R>(&'a self, f: impl FnOnce(&'a mut T) -> R) -> R {
+        loop {
+            // Loop until acquired the lock
+            if let Ok(false) =
+                self.lock
+                    .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
+            {
+                break;
+            }
+        }
+        let data = unsafe { &mut *self.data.get() };
+
+        let res = f(data);
+        // Release the lock after finished with the underlying data
+        self.lock.store(false, Ordering::Release);
+        res
+    }
+}
-- 
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