use std::cell::UnsafeCell;
use std::fmt::Debug;
use std::marker::PhantomData;
use std::panic::AssertUnwindSafe;
use lock_api::RawMutex;
use crate::handle_unwind::handle_unwind;
use crate::lockable::{Lockable, LockableGetMut, LockableIntoInner, OwnedLockable, RawLock};
use crate::poisonable::PoisonFlag;
use crate::{Keyable, ThreadKey};
use super::{Mutex, MutexGuard, MutexRef};
unsafe impl<T: ?Sized, R: RawMutex> RawLock for Mutex<T, R> {
fn poison(&self) {
self.poison.poison();
}
unsafe fn raw_write(&self) {
assert!(!self.poison.is_poisoned(), "The mutex has been killed");
// if the closure unwraps, then the mutex will be killed
let this = AssertUnwindSafe(self);
handle_unwind(|| this.raw.lock(), || self.poison())
}
unsafe fn raw_try_write(&self) -> bool {
if self.poison.is_poisoned() {
return false;
}
// if the closure unwraps, then the mutex will be killed
let this = AssertUnwindSafe(self);
handle_unwind(|| this.raw.try_lock(), || self.poison())
}
unsafe fn raw_unlock_write(&self) {
// if the closure unwraps, then the mutex will be killed
let this = AssertUnwindSafe(self);
handle_unwind(|| this.raw.unlock(), || self.poison())
}
// this is the closest thing to a read we can get, but Sharable isn't
// implemented for this
#[mutants::skip]
#[cfg(not(tarpaulin_include))]
unsafe fn raw_read(&self) {
self.raw_write()
}
#[mutants::skip]
#[cfg(not(tarpaulin_include))]
unsafe fn raw_try_read(&self) -> bool {
self.raw_try_write()
}
#[mutants::skip]
#[cfg(not(tarpaulin_include))]
unsafe fn raw_unlock_read(&self) {
self.raw_unlock_write()
}
}
unsafe impl<T, R: RawMutex> Lockable for Mutex<T, R> {
type Guard<'g>
= MutexRef<'g, T, R>
where
Self: 'g;
type DataMut<'a>
= &'a mut T
where
Self: 'a;
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 data_mut(&self) -> Self::DataMut<'_> {
self.data.get().as_mut().unwrap_unchecked()
}
}
impl<T, R: RawMutex> LockableIntoInner for Mutex<T, R> {
type Inner = T;
fn into_inner(self) -> Self::Inner {
self.into_inner()
}
}
impl<T, R: RawMutex> LockableGetMut for Mutex<T, R> {
type Inner<'a>
= &'a mut T
where
Self: 'a;
fn get_mut(&mut self) -> Self::Inner<'_> {
self.get_mut()
}
}
unsafe impl<T, R: RawMutex> OwnedLockable for Mutex<T, R> {}
impl<T, R: RawMutex> Mutex<T, R> {
/// Creates a `Mutex` in an unlocked state ready for use.
///
/// # 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
}
}
#[mutants::skip]
#[cfg(not(tarpaulin_include))]
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!
// We have it anyway for documentation
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> {
/// Acquires a lock on the mutex, blocking until it is safe to do so, and then
/// unlocks the mutex after the provided function returns.
///
/// This function is useful to ensure that a Mutex is never accidentally
/// locked forever by leaking the `MutexGuard`. Even if the function panics,
/// this function will gracefully notice the panic, and unlock the mutex.
///
/// # Panics
///
/// This function will panic if the provided function also panics. However,
/// mutex will be safely unlocked in this case, allowing the mutex to be
/// locked again later.
///
/// # Example
///
/// ```
/// use happylock::{ThreadKey, Mutex};
///
/// let mut key = ThreadKey::get().unwrap();
/// let mutex = Mutex::new(42);
///
/// let x = mutex.scoped_lock(&mut key, |number| {
/// *number += 5;
/// *number
/// });
/// assert_eq!(x, 47);
/// ```
pub fn scoped_lock<'a, Ret>(
&'a self,
key: impl Keyable,
f: impl FnOnce(&'a mut T) -> Ret,
) -> Ret {
unsafe {
// safety: we have the key
self.raw_write();
// safety: the data has been locked
let r = handle_unwind(
|| f(self.data.get().as_mut().unwrap_unchecked()),
|| self.raw_unlock_write(),
);
// ensures the key is held long enough
drop(key);
// safety: the mutex is still locked
self.raw_unlock_write();
r
}
}
/// Attempts to acquire the `Mutex` without blocking, and then unlocks it once
/// the provided function returns.
///
/// This function implements a non-blocking variant of [`scoped_lock`]. Unlike
/// `scoped_lock`, if the mutex is not already unlocked, then the provided
/// function will not run, and the given [`Keyable`] is returned.
///
/// # Errors
///
/// If the mutex is already locked, then the provided function will not run.
/// `Err` is returned with the given key.
///
/// # Panics
///
/// If the provided function panics, then the panic will be bubbled up and
/// rethrown. The mutex will also be gracefully unlocked, allowing the mutex
/// to be locked again.
///
/// # Examples
///
/// ```
/// use happylock::{Mutex, ThreadKey};
///
/// let mut key = ThreadKey::get().unwrap();
/// let mutex = Mutex::new(42);
///
/// let result = mutex.scoped_try_lock(&mut key, |num| {
/// *num
/// });
///
/// match result {
/// Ok(val) => println!("The number is {val}"),
/// Err(_) => unreachable!(),
/// }
/// ```
pub fn scoped_try_lock<'a, Key: Keyable, Ret>(
&'a self,
key: Key,
f: impl FnOnce(&'a mut T) -> Ret,
) -> Result<Ret, Key> {
unsafe {
// safety: we have the key
if !self.raw_try_write() {
return Err(key);
}
// safety: the data has been locked
let r = handle_unwind(
|| f(self.data.get().as_mut().unwrap_unchecked()),
|| self.raw_unlock_write(),
);
// ensures the key is held long enough
drop(key);
// safety: the mutex is still locked
self.raw_unlock_write();
Ok(r)
}
}
}
impl<T: ?Sized, R: RawMutex> Mutex<T, R> {
/// Acquires a mutex, blocking the current thread until it is able to do so.
///
/// This function will block the local thread until it is available to acquire
/// the mutex. Upon returning, the thread is the only thread with the lock
/// held. A [`MutexGuard`] is returned to allow a scoped unlock of this
/// `Mutex`. When the guard goes out of scope, this `Mutex` will unlock.
///
/// Due to the requirement of a [`ThreadKey`] to call this function, it is not
/// possible for this function to deadlock.
///
/// # Examples
///
/// ```
/// use std::thread;
/// use happylock::{Mutex, ThreadKey};
///
/// let mutex = Mutex::new(0);
///
/// thread::scope(|s| {
/// s.spawn(|| {
/// let key = ThreadKey::get().unwrap();
/// *mutex.lock(key) = 10;
/// });
/// });
///
/// let key = ThreadKey::get().unwrap();
/// assert_eq!(*mutex.lock(key), 10);
/// ```
pub fn lock(&self, key: ThreadKey) -> MutexGuard<'_, T, R> {
unsafe {
// safety: we have the thread key
self.raw_write();
// safety: we just locked the mutex
MutexGuard::new(self, key)
}
}
/// Attempts to lock this `Mutex` without blocking.
///
/// If the lock could not be acquired at this time, then `Err` is returned.
/// Otherwise, an RAII guard is returned. The lock will be unlocked when the
/// guard is dropped.
///
/// # Errors
///
/// If the mutex could not be acquired because it is already locked, then
/// this call will return an error containing the [`ThreadKey`].
///
/// # Examples
///
/// ```
/// use std::thread;
/// use happylock::{Mutex, ThreadKey};
///
/// let mutex = Mutex::new(0);
///
/// thread::scope(|s| {
/// s.spawn(|| {
/// let key = ThreadKey::get().unwrap();
/// let mut lock = mutex.try_lock(key);
/// if let Ok(mut lock) = lock {
/// *lock = 10;
/// } else {
/// println!("try_lock failed");
/// }
/// });
/// });
///
/// let key = ThreadKey::get().unwrap();
/// assert_eq!(*mutex.lock(key), 10);
/// ```
pub fn try_lock(&self, key: ThreadKey) -> Result<MutexGuard<'_, T, R>, ThreadKey> {
unsafe {
// safety: we have the key to the mutex
if self.raw_try_write() {
// safety: we just locked the mutex
Ok(MutexGuard::new(self, key))
} else {
Err(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_write().then_some(MutexRef(self, PhantomData))
}
/// Consumes the [`MutexGuard`], and consequently unlocks its `Mutex`.
///
/// This function is equivalent to calling [`drop`] on the guard, except that
/// it returns the key that was used to create it. Alernatively, the guard
/// will be automatically dropped when it goes out of scope.
///
/// # 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);
///
/// let guard = mutex.lock(key);
/// assert_eq!(*guard, 20);
/// ```
#[must_use]
pub fn unlock(guard: MutexGuard<'_, T, R>) -> ThreadKey {
drop(guard.mutex);
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> {}
|
