50 lines
1.3 KiB
Rust
50 lines
1.3 KiB
Rust
//! Synchronization types.
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//!
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//! Most importantly, a fair mutex is included.
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use parking_lot::{Mutex, MutexGuard};
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/// A fair mutex.
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///
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/// Uses an extra lock to ensure that if one thread is waiting that it will get
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/// the lock before a single thread can re-lock it.
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pub struct FairMutex<T> {
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/// Data.
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data: Mutex<T>,
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/// Next-to-access.
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next: Mutex<()>,
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}
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impl<T> FairMutex<T> {
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/// Create a new fair mutex.
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pub fn new(data: T) -> FairMutex<T> {
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FairMutex { data: Mutex::new(data), next: Mutex::new(()) }
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}
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/// Acquire a lease to reserve the mutex lock.
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///
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/// This will prevent others from acquiring a terminal lock, but block if anyone else is
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/// already holding a lease.
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pub fn lease(&self) -> MutexGuard<'_, ()> {
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self.next.lock()
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}
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/// Lock the mutex.
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pub fn lock(&self) -> MutexGuard<'_, T> {
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// Must bind to a temporary or the lock will be freed before going
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// into data.lock().
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let _next = self.next.lock();
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self.data.lock()
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}
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/// Unfairly lock the mutex.
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pub fn lock_unfair(&self) -> MutexGuard<'_, T> {
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self.data.lock()
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}
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/// Unfairly try to lock the mutex.
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pub fn try_lock_unfair(&self) -> Option<MutexGuard<'_, T>> {
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self.data.try_lock()
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}
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}
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