use std::fmt::Debug;
use std::{cell::UnsafeCell, marker::PhantomData};
use lock_api::RawMutex;
use crate::key::Keyable;
use super::{Mutex, MutexGuard, MutexRef};
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,
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
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: ?Sized + 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)
}
}
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<'_, 'k, T, Key, R> {
unsafe {
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<'_, 'k, T, Key, R>> {
if self.raw.try_lock() {
// safety: we just locked the mutex
Some(unsafe { MutexGuard::new(self, key) })
} else {
None
}
}
/// 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))
}
/// Forcibly unlocks the `Lock`.
///
/// # Safety
///
/// This should only be called if there are no references to any
/// [`MutexGuard`]s for this mutex in the program.
pub(super) unsafe fn force_unlock(&self) {
self.raw.unlock();
}
/// 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.force_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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