Add a Mutex implementation.

rust/lib/mammoth/src/sync.rs

@@ -1,3 +1,7 @@
+use core::cell::UnsafeCell;
+use core::ops::Deref;
+use core::ops::DerefMut;
+
 use crate::{cap::Capability, syscall, zion::ZError};
 
 pub struct Semaphore {
@@ -17,3 +21,52 @@ impl Semaphore {
         syscall::semaphone_signal(&self.cap)
     }
 }
+
+pub struct Mutex<T> {
+    cap: Capability,
+    data: UnsafeCell<T>,
+}
+
+unsafe impl<T> Sync for Mutex<T> where T: Send {}
+
+pub struct MutexGuard<'a, T> {
+    mutex: &'a Mutex<T>,
+}
+
+unsafe impl<T> Send for MutexGuard<'_, T> where T: Send {}
+unsafe impl<T> Sync for MutexGuard<'_, T> where T: Sync {}
+
+impl<T> Deref for MutexGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        unsafe { &*self.mutex.data.get() }
+    }
+}
+
+impl<T> DerefMut for MutexGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { &mut *self.mutex.data.get() }
+    }
+}
+
+impl<T> Mutex<T> {
+    pub fn new(data: T) -> Mutex<T> {
+        Mutex {
+            cap: syscall::mutex_create().unwrap(),
+            data: UnsafeCell::new(data),
+        }
+    }
+
+    pub fn lock(&self) -> MutexGuard<T> {
+        syscall::mutex_lock(&self.cap).unwrap();
+
+        MutexGuard { mutex: self }
+    }
+}
+
+impl<T> Drop for MutexGuard<'_, T> {
+    fn drop(&mut self) {
+        syscall::mutex_release(&self.mutex.cap).unwrap();
+    }
+}