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use crate::future::poll_fn;
use crate::sync::semaphore_ll as semaphore;
use std::cell::UnsafeCell;
use std::error::Error;
use std::fmt;
use std::ops::{Deref, DerefMut};
#[derive(Debug)]
pub struct Mutex<T> {
c: UnsafeCell<T>,
s: semaphore::Semaphore,
}
pub struct MutexGuard<'a, T> {
lock: &'a Mutex<T>,
permit: semaphore::Permit,
}
unsafe impl<T> Send for Mutex<T> where T: Send {}
unsafe impl<T> Sync for Mutex<T> where T: Send {}
unsafe impl<'a, T> Sync for MutexGuard<'a, T> where T: Send + Sync {}
#[derive(Debug)]
pub struct TryLockError(());
impl fmt::Display for TryLockError {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(fmt, "{}", "operation would block")
}
}
impl Error for TryLockError {}
#[test]
#[cfg(not(loom))]
fn bounds() {
fn check<T: Send>() {}
check::<MutexGuard<'_, u32>>();
}
impl<T> Mutex<T> {
pub fn new(t: T) -> Self {
Self {
c: UnsafeCell::new(t),
s: semaphore::Semaphore::new(1),
}
}
pub async fn lock(&self) -> MutexGuard<'_, T> {
let mut guard = MutexGuard {
lock: self,
permit: semaphore::Permit::new(),
};
poll_fn(|cx| guard.permit.poll_acquire(cx, &self.s))
.await
.unwrap_or_else(|_| {
unreachable!()
});
guard
}
pub fn try_lock(&self) -> Result<MutexGuard<'_, T>, TryLockError> {
let mut permit = semaphore::Permit::new();
match permit.try_acquire(&self.s) {
Ok(_) => Ok(MutexGuard { lock: self, permit }),
Err(_) => Err(TryLockError(())),
}
}
}
impl<'a, T> Drop for MutexGuard<'a, T> {
fn drop(&mut self) {
self.permit.release(&self.lock.s);
}
}
impl<T> From<T> for Mutex<T> {
fn from(s: T) -> Self {
Self::new(s)
}
}
impl<T> Default for Mutex<T>
where
T: Default,
{
fn default() -> Self {
Self::new(T::default())
}
}
impl<'a, T> Deref for MutexGuard<'a, T> {
type Target = T;
fn deref(&self) -> &Self::Target {
assert!(self.permit.is_acquired());
unsafe { &*self.lock.c.get() }
}
}
impl<'a, T> DerefMut for MutexGuard<'a, T> {
fn deref_mut(&mut self) -> &mut Self::Target {
assert!(self.permit.is_acquired());
unsafe { &mut *self.lock.c.get() }
}
}
impl<'a, T: fmt::Debug> fmt::Debug for MutexGuard<'a, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&**self, f)
}
}
impl<'a, T: fmt::Display> fmt::Display for MutexGuard<'a, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Display::fmt(&**self, f)
}
}