From af9a7aa7124300882f023c33d1b9e01f5a78c22c Mon Sep 17 00:00:00 2001
From: Julien CLEMENT <julien.clement@epita.fr>
Date: Tue, 20 Dec 2022 20:38:18 +0100
Subject: [PATCH] Add async mutex first version

Signed-off-by: Julien CLEMENT <julien.clement@epita.fr>
---
 src/lib.rs         |   2 -
 src/utils/mod.rs   |   4 +-
 src/utils/mutex.rs | 111 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 114 insertions(+), 3 deletions(-)
 create mode 100644 src/utils/mutex.rs

diff --git a/src/lib.rs b/src/lib.rs
index 58db943..0c74136 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -19,8 +19,6 @@ use drivers::vga::{self, Color, ColorCode};
 use multiboot2::BootInformation;
 use task::{executor::Executor, keyboard, Task};
 
-use fs::iso::iso9660::{IsoDir, IsoPrimVolDesc, MultiEndian32};
-
 #[alloc_error_handler]
 fn alloc_error_handler(layout: alloc::alloc::Layout) -> ! {
     panic!("Allocation error: {:?}", layout)
diff --git a/src/utils/mod.rs b/src/utils/mod.rs
index c2664f7..bfc745d 100644
--- a/src/utils/mod.rs
+++ b/src/utils/mod.rs
@@ -1,3 +1,5 @@
 pub mod serialize;
+pub mod mutex;
 
-pub use serialize::unserialize;
\ No newline at end of file
+pub use serialize::unserialize;
+pub use mutex::AsyncMutex;
\ No newline at end of file
diff --git a/src/utils/mutex.rs b/src/utils/mutex.rs
new file mode 100644
index 0000000..6250f71
--- /dev/null
+++ b/src/utils/mutex.rs
@@ -0,0 +1,111 @@
+use core::future::Future;
+use core::pin::Pin;
+use core::cell::UnsafeCell;
+use core::ops::{Deref, DerefMut, Drop};
+use core::sync::atomic::{AtomicBool, Ordering};
+use core::task::{Context, Poll};
+use alloc::rc::Rc;
+
+use futures_util::task::AtomicWaker;
+
+#[derive(Clone)]
+struct Lock {
+    lock: Rc<AtomicBool>,
+    waker: Rc<AtomicWaker>,
+}
+
+pub struct AsyncMutex<T> {
+    lock: Lock,
+    inner: UnsafeCell<T>,
+}
+
+pub struct AsyncMutexGuard<'a, T>
+where
+    T: 'a,
+{
+    mutex: &'a AsyncMutex<T>
+}
+
+impl Lock {
+    fn new() -> Self {
+        Lock {
+            lock: Rc::new(AtomicBool::new(false)),
+            waker: Rc::new(AtomicWaker::new()),
+        }
+    }
+
+    fn try_lock(&self) -> bool {
+        self.lock.swap(true, Ordering::Acquire)
+    }
+
+    fn drop(&self) {
+        self.lock.swap(false, Ordering::Release);
+        self.waker.wake();
+    }
+}
+
+impl Future for Lock {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
+        if self.try_lock() {
+            return Poll::Ready(());
+        }
+
+        self.waker.register(&cx.waker());
+
+        match self.try_lock() {
+            true => {
+                self.waker.take();
+                Poll::Ready(())
+            },
+            false => Poll::Pending,
+        }
+    }
+}
+
+impl<T> AsyncMutex<T> {
+    pub fn new(val: T) -> Self {
+        AsyncMutex {
+            lock: Lock::new(),
+            inner: UnsafeCell::new(val),
+        }
+    }
+
+    pub fn try_lock(&self) -> Option<AsyncMutexGuard<T>> {
+        if self.lock.try_lock() {
+            Some(AsyncMutexGuard { mutex: self })
+        } else {
+            None
+        }
+    }
+
+    pub async fn lock(&self) -> AsyncMutexGuard<'_, T> {
+        self.lock.clone().await;
+        AsyncMutexGuard { mutex: self }
+    }
+}
+
+
+impl<T> Drop for AsyncMutexGuard<'_, T> {
+    fn drop(&mut self) {
+        self.mutex.lock.drop();
+    }
+}
+
+impl<T> Deref for AsyncMutexGuard<'_, T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        unsafe {
+            &*self.mutex.inner.get()
+        }
+    }
+}
+
+impl<T> DerefMut for AsyncMutexGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe {
+            &mut *self.mutex.inner.get()
+        }
+    }
+}
\ No newline at end of file