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use core::sync::atomic::{AtomicBool, Ordering};
use core::ops::{Deref, DerefMut};
use core::cell::UnsafeCell;
use crate::syscall;
use crate::sched::event;
use super::Error;
pub struct Mutex<T> {
id: UnsafeCell<usize>,
inner: UnsafeCell<T>,
lock: AtomicBool,
}
impl<T> Mutex<T> {
pub fn new(element: T) -> Self {
let mutex = Mutex {
id: UnsafeCell::new(0),
inner: UnsafeCell::new(element),
lock: AtomicBool::new(false),
};
mutex.register().ok();
mutex
}
fn register(&self) -> Result<(),Error> {
let id = syscall::event_register();
if id == 0 {
Err(Error::OutOfMemory)
} else {
unsafe { self.id.get().write(id); }
Ok(())
}
}
pub fn try_lock(&self) -> Result<MutexGuard<'_,T>, Error> {
if self.raw_try_lock() {
Ok(MutexGuard::new(&self))
} else {
Err(Error::WouldBlock)
}
}
pub fn lock(&self, timeout: u32) -> Result<MutexGuard<'_,T>, Error> {
if self.raw_try_lock() {
return Ok(MutexGuard::new(&self));
} else {
let id = unsafe { *self.id.get() };
match syscall::event_await(id, timeout) {
Ok(_) => {
self.raw_try_lock();
Ok(MutexGuard::new(&self))
},
Err(event::Error::TimeOut) => Err(Error::TimeOut),
Err(_) => Err(Error::Poisoned),
}
}
}
fn raw_try_lock(&self) -> bool {
self.lock.compare_exchange(false, true,
Ordering::Acquire,
Ordering::Relaxed).is_ok()
}
fn raw_unlock(&self) {
self.lock.store(false, Ordering::Release);
syscall::event_fire(unsafe { *self.id.get() });
}
}
unsafe impl<T> Sync for Mutex<T> {}
pub struct MutexGuard<'a,T> {
lock: &'a Mutex<T>,
}
impl<'a,T> MutexGuard<'a,T> {
fn new(lock: &'a Mutex<T>) -> Self {
MutexGuard {
lock,
}
}
}
impl<'a,T> Deref for MutexGuard<'a,T> {
type Target = T;
fn deref(&self) -> &Self::Target {
unsafe { &*self.lock.inner.get() }
}
}
impl<'a,T> DerefMut for MutexGuard<'a,T> {
fn deref_mut(&mut self) -> &mut Self::Target {
unsafe { &mut *self.lock.inner.get() }
}
}
impl<'a,T> Drop for MutexGuard<'a,T> {
fn drop(&mut self) {
self.lock.raw_unlock();
}
}