From 25ac075ef13587125571c539faa72366d189f7df Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Tue, 22 Mar 2022 09:54:44 +0100
Subject: [PATCH] mutex

---
 src/lib.rs         |  3 ++-
 src/linked_list.rs | 18 +++++++++++++++
 src/mutex.rs       | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+), 1 deletion(-)
 create mode 100644 src/linked_list.rs
 create mode 100644 src/mutex.rs

diff --git a/src/lib.rs b/src/lib.rs
index 64a29b3..68873ae 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1 +1,2 @@
-compile_error!("lol");
+mod linked_list;
+mod mutex;
diff --git a/src/linked_list.rs b/src/linked_list.rs
new file mode 100644
index 0000000..ad10414
--- /dev/null
+++ b/src/linked_list.rs
@@ -0,0 +1,18 @@
+use std::ptr;
+use std::sync::atomic::AtomicPtr;
+
+pub struct LinkedList<T> {
+    head: AtomicPtr<Node<T>>,
+}
+
+struct Node<T> {
+    next: AtomicPtr<Node<T>>,
+}
+
+impl<T> LinkedList<T> {
+    pub fn new() -> Self {
+        Self {
+            head: AtomicPtr::new(ptr::null_mut()),
+        }
+    }
+}
diff --git a/src/mutex.rs b/src/mutex.rs
new file mode 100644
index 0000000..f52701b
--- /dev/null
+++ b/src/mutex.rs
@@ -0,0 +1,55 @@
+use std::cell::UnsafeCell;
+use std::ops::{Deref, DerefMut};
+use std::sync::atomic::{AtomicU8, Ordering};
+
+const INIT: u8 = 0;
+const ACQUIRED: u8 = 1;
+
+struct Mutex<T> {
+    value: UnsafeCell<T>,
+    status: AtomicU8,
+}
+
+impl<T> Mutex<T> {
+    pub fn new(value: T) -> Self {
+        Self {
+            value,
+            status: AtomicU8::new(INIT),
+        }
+    }
+
+    pub fn try_lock(&self) -> Option<MutexGuard<'_, T>> {
+        if self
+            .status
+            .compare_exchange(INIT, ACQUIRED, Ordering::Acquire, Ordering::Relaxed)
+        {
+            Some(MutexGuard { mutex: self })
+        } else {
+            None
+        }
+    }
+}
+
+pub struct MutexGuard<'a, T> {
+    mutex: &'a Mutex<T>,
+}
+
+impl<'a, T> Deref for MutexGuard<'a, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        unsafe { &*self.mutex.value.get() }
+    }
+}
+
+impl<'a, T> DerefMut for MutexGuard<'a, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { &mut *self.mutex.value.get() }
+    }
+}
+
+impl<'a, T> Drop for MutexGuard<'a, T> {
+    fn drop(&mut self) {
+        self.mutex.status.store(INIT, Ordering::Release);
+    }
+}