use std::cell::UnsafeCell;
use std::fmt::Debug;
use std::marker::PhantomData;
use lock_api::RawMutex;
use crate::key::Keyable;
use crate::lockable::{Lockable, LockableAsMut, LockableIntoInner, OwnedLockable, RawLock};
use crate::poisonable::PoisonFlag;
use super::{Mutex, MutexGuard, MutexRef};
unsafe impl<T: ?Sized, R: RawMutex> RawLock for Mutex<T, R> {
fn kill(&self) {
self.poison.poison();
}
unsafe fn raw_lock(&self) {
assert!(!self.poison.is_poisoned(), "The mutex has been killed");
scopeguard::defer_on_unwind! {
scopeguard::defer_on_unwind! { self.kill() };
if self.raw_try_lock() {
self.raw_unlock();
} else {
// We don't know whether this lock is locked by the current
// thread, or another thread. There's not much we can do other
// than kill it.
self.kill();
}
}
self.raw.lock()
}
unsafe fn raw_try_lock(&self) -> bool {
if self.poison.is_poisoned() {
return false;
}
scopeguard::defer_on_unwind! {
scopeguard::defer_on_unwind! { self.kill() };
if self.raw_try_lock() {
self.raw_unlock();
} else {
// We don't know whether this lock is locked by the current
// thread, or another thread. There's not much we can do other
// than kill it.
self.kill();
}
}
self.raw.try_lock()
}
unsafe fn raw_unlock(&self) {
scopeguard::defer_on_unwind! {
scopeguard::defer_on_unwind! { self.kill() };
if self.raw_try_lock() {
self.raw_unlock();
} else {
// We don't know whether this lock is locked by the current
// thread, or another thread. There's not much we can do other
// than kill it.
self.kill();
}
}
self.raw.unlock()
}
// this is the closest thing to a read we can get, but Sharable isn't
// implemented for this
unsafe fn raw_read(&self) {
self.raw_lock()
}
unsafe fn raw_try_read(&self) -> bool {
self.raw_try_lock()
}
unsafe fn raw_unlock_read(&self) {
self.raw_unlock()
}
}
unsafe impl<T: Send, R: RawMutex + Send + Sync> Lockable for Mutex<T, R> {
type Guard<'g>
= MutexRef<'g, T, R>
where
Self: 'g;
type ReadGuard<'g>
= MutexRef<'g, T, R>
where
Self: 'g;
fn get_ptrs<'a>(&'a self, ptrs: &mut Vec<&'a dyn RawLock>) {
ptrs.push(self);
}
unsafe fn guard(&self) -> Self::Guard<'_> {
MutexRef::new(self)
}
unsafe fn read_guard(&self) -> Self::ReadGuard<'_> {
MutexRef::new(self)
}
}
impl<T: Send, R: RawMutex + Send + Sync> LockableIntoInner for Mutex<T, R> {
type Inner = T;
fn into_inner(self) -> Self::Inner {
self.into_inner()
}
}
impl<T: Send, R: RawMutex + Send + Sync> LockableAsMut for Mutex<T, R> {
type Inner<'a>
= &'a mut T
where
Self: 'a;
fn as_mut(&mut self) -> Self::Inner<'_> {
self.get_mut()
}
}
unsafe impl<T: Send, R: RawMutex + Send + Sync> OwnedLockable for Mutex<T, R> {}
impl<T, R: RawMutex> Mutex<T, R> {
/// Create a new unlocked `Mutex`.
///
/// # Examples
///
/// ```
/// use happylock::Mutex;
///
/// let mutex = Mutex::new(0);
/// ```
#[must_use]
pub const fn new(data: T) -> Self {
Self {
raw: R::INIT,
poison: PoisonFlag::new(),
data: UnsafeCell::new(data),
}
}
/// Returns the raw underlying mutex.
///
/// Note that you will most likely need to import the [`RawMutex`] trait
/// from `lock_api` to be able to call functions on the raw mutex.
///
/// # Safety
///
/// This method is unsafe because it allows unlocking a mutex while still
/// holding a reference to a [`MutexGuard`], and locking a mutex without
/// holding the [`ThreadKey`].
///
/// [`ThreadKey`]: `crate::ThreadKey`
#[must_use]
pub const unsafe fn raw(&self) -> &R {
&self.raw
}
}
impl<T: ?Sized + Debug, R: RawMutex> Debug for Mutex<T, R> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
// safety: this is just a try lock, and the value is dropped
// immediately after, so there's no risk of blocking ourselves
// or any other threads
// when i implement try_clone this code will become less unsafe
if let Some(value) = unsafe { self.try_lock_no_key() } {
f.debug_struct("Mutex").field("data", &&*value).finish()
} else {
struct LockedPlaceholder;
impl Debug for LockedPlaceholder {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str("<locked>")
}
}
f.debug_struct("Mutex")
.field("data", &LockedPlaceholder)
.finish()
}
}
}
impl<T: Default, R: RawMutex> Default for Mutex<T, R> {
fn default() -> Self {
Self::new(T::default())
}
}
impl<T, R: RawMutex> From<T> for Mutex<T, R> {
fn from(value: T) -> Self {
Self::new(value)
}
}
// We don't need a `get_mut` because we don't have mutex poisoning. Hurray!
// This is safe because you can't have a mutable reference to the lock if it's
// locked. Being locked requires an immutable reference because of the guard.
impl<T: ?Sized, R> AsMut<T> for Mutex<T, R> {
fn as_mut(&mut self) -> &mut T {
self.get_mut()
}
}
impl<T, R> Mutex<T, R> {
/// Consumes this mutex, returning the underlying data.
///
/// # Examples
///
/// ```
/// use happylock::Mutex;
///
/// let mutex = Mutex::new(0);
/// assert_eq!(mutex.into_inner(), 0);
/// ```
#[must_use]
pub fn into_inner(self) -> T {
self.data.into_inner()
}
}
impl<T: ?Sized, R> Mutex<T, R> {
/// Returns a mutable reference to the underlying data.
///
/// Since this call borrows `Mutex` mutably, no actual locking is taking
/// place. The mutable borrow statically guarantees that no locks exist.
///
/// # Examples
///
/// ```
/// use happylock::{ThreadKey, Mutex};
///
/// let key = ThreadKey::get().unwrap();
/// let mut mutex = Mutex::new(0);
/// *mutex.get_mut() = 10;
/// assert_eq!(*mutex.lock(key), 10);
/// ```
#[must_use]
pub fn get_mut(&mut self) -> &mut T {
self.data.get_mut()
}
}
impl<T: ?Sized, R: RawMutex> Mutex<T, R> {
/// Block the thread until this mutex can be locked, and lock it.
///
/// Upon returning, the thread is the only thread with a lock on the
/// `Mutex`. A [`MutexGuard`] is returned to allow a scoped unlock of this
/// `Mutex`. When the guard is dropped, this `Mutex` will unlock.
///
/// # Examples
///
/// ```
/// use std::{thread, sync::Arc};
/// use happylock::{Mutex, ThreadKey};
///
/// let mutex = Arc::new(Mutex::new(0));
/// let c_mutex = Arc::clone(&mutex);
///
/// thread::spawn(move || {
/// let key = ThreadKey::get().unwrap();
/// *c_mutex.lock(key) = 10;
/// }).join().expect("thread::spawn failed");
///
/// let key = ThreadKey::get().unwrap();
/// assert_eq!(*mutex.lock(key), 10);
/// ```
pub fn lock<'s, 'k: 's, Key: Keyable>(&'s self, key: Key) -> MutexGuard<'s, 'k, T, Key, R> {
unsafe {
// safety: we have the thread key
self.raw_lock();
// safety: we just locked the mutex
MutexGuard::new(self, key)
}
}
/// Attempts to lock the `Mutex` without blocking.
///
/// # Errors
///
/// Returns [`Err`] if the `Mutex` cannot be locked without blocking.
///
/// # Examples
///
/// ```
/// use std::{thread, sync::Arc};
/// use happylock::{Mutex, ThreadKey};
///
/// let mutex = Arc::new(Mutex::new(0));
/// let c_mutex = Arc::clone(&mutex);
///
/// thread::spawn(move || {
/// let key = ThreadKey::get().unwrap();
/// let mut lock = c_mutex.try_lock(key);
/// if let Some(mut lock) = lock {
/// *lock = 10;
/// } else {
/// println!("try_lock failed");
/// }
/// }).join().expect("thread::spawn failed");
///
/// let key = ThreadKey::get().unwrap();
/// assert_eq!(*mutex.lock(key), 10);
/// ```
pub fn try_lock<'s, 'a: 's, 'k: 'a, Key: Keyable>(
&'s self,
key: Key,
) -> Option<MutexGuard<'s, 'k, T, Key, R>> {
unsafe {
// safety: we have the key to the mutex
self.raw_try_lock().then(||
// safety: we just locked the mutex
MutexGuard::new(self, key))
}
}
/// Returns `true` if the mutex is currently locked
#[cfg(test)]
pub(crate) fn is_locked(&self) -> bool {
self.raw.is_locked()
}
/// Lock without a [`ThreadKey`]. It is undefined behavior to do this without
/// owning the [`ThreadKey`].
pub(crate) unsafe fn try_lock_no_key(&self) -> Option<MutexRef<'_, T, R>> {
self.raw_try_lock().then_some(MutexRef(self, PhantomData))
}
/// Consumes the [`MutexGuard`], and consequently unlocks its `Mutex`.
///
/// # Examples
///
/// ```
/// use happylock::{ThreadKey, Mutex};
///
/// let key = ThreadKey::get().unwrap();
/// let mutex = Mutex::new(0);
///
/// let mut guard = mutex.lock(key);
/// *guard += 20;
///
/// let key = Mutex::unlock(guard);
/// ```
pub fn unlock<'a, 'k: 'a, Key: Keyable + 'k>(guard: MutexGuard<'a, 'k, T, Key, R>) -> Key {
unsafe {
guard.mutex.0.raw_unlock();
}
guard.thread_key
}
}
unsafe impl<R: RawMutex + Send, T: ?Sized + Send> Send for Mutex<T, R> {}
unsafe impl<R: RawMutex + Sync, T: ?Sized + Send> Sync for Mutex<T, R> {}
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