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use crate::sys::mutex as imp;
/// An OS-based mutual exclusion lock, meant for use in static variables.
///
/// This mutex has a const constructor ([`StaticMutex::new`]), does not
/// implement `Drop` to cleanup resources, and causes UB when moved or used
/// reentrantly.
///
/// This mutex does not implement poisoning.
///
/// This is a wrapper around `imp::Mutex` that does *not* call `init()` and
/// `destroy()`.
pub struct StaticMutex(imp::Mutex);
unsafe impl Sync for StaticMutex {}
impl StaticMutex {
/// Creates a new mutex for use.
///
/// Behavior is undefined if the mutex is moved after it is
/// first used with any of the functions below.
/// Also, the behavior is undefined if this mutex is ever used reentrantly,
/// i.e., `lock` is called by the thread currently holding the lock.
#[rustc_const_stable(feature = "const_sys_mutex_new", since = "1.0.0")]
pub const fn new() -> Self {
Self(imp::Mutex::new())
}
/// Calls raw_lock() and then returns an RAII guard to guarantee the mutex
/// will be unlocked.
///
/// It is undefined behaviour to call this function while locked, or if the
/// mutex has been moved since the last time this was called.
#[inline]
pub unsafe fn lock(&self) -> StaticMutexGuard<'_> {
self.0.lock();
StaticMutexGuard(&self.0)
}
}
#[must_use]
pub struct StaticMutexGuard<'a>(&'a imp::Mutex);
impl Drop for StaticMutexGuard<'_> {
#[inline]
fn drop(&mut self) {
unsafe {
self.0.unlock();
}
}
}
/// An OS-based mutual exclusion lock.
///
/// This mutex does *not* have a const constructor, cleans up its resources in
/// its `Drop` implementation, may safely be moved (when not borrowed), and
/// does not cause UB when used reentrantly.
///
/// This mutex does not implement poisoning.
///
/// This is a wrapper around `Box<imp::Mutex>`, to allow the object to be moved
/// without moving the raw mutex.
pub struct MovableMutex(Box<imp::Mutex>);
unsafe impl Sync for MovableMutex {}
impl MovableMutex {
/// Creates a new mutex.
pub fn new() -> Self {
let mut mutex = box imp::Mutex::new();
unsafe { mutex.init() };
Self(mutex)
}
pub(crate) fn raw(&self) -> &imp::Mutex {
&self.0
}
/// Locks the mutex blocking the current thread until it is available.
#[inline]
pub fn raw_lock(&self) {
unsafe { self.0.lock() }
}
/// Attempts to lock the mutex without blocking, returning whether it was
/// successfully acquired or not.
#[inline]
pub fn try_lock(&self) -> bool {
unsafe { self.0.try_lock() }
}
/// Unlocks the mutex.
///
/// Behavior is undefined if the current thread does not actually hold the
/// mutex.
#[inline]
pub unsafe fn raw_unlock(&self) {
self.0.unlock()
}
}
impl Drop for MovableMutex {
fn drop(&mut self) {
unsafe { self.0.destroy() };
}
}
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