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// Copyright 2016 Joe Wilm, The Alacritty Project Contributors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Synchronization types.
//!
//! Most importantly, a fair mutex is included.
use parking_lot::{Mutex, MutexGuard};
/// A fair mutex.
///
/// Uses an extra lock to ensure that if one thread is waiting that it will get
/// the lock before a single thread can re-lock it.
pub struct FairMutex<T> {
/// Data.
data: Mutex<T>,
/// Next-to-access.
next: Mutex<()>,
}
impl<T> FairMutex<T> {
/// Create a new fair mutex.
pub fn new(data: T) -> FairMutex<T> {
FairMutex { data: Mutex::new(data), next: Mutex::new(()) }
}
/// Lock the mutex.
pub fn lock(&self) -> MutexGuard<'_, T> {
// Must bind to a temporary or the lock will be freed before going
// into data.lock().
let _next = self.next.lock();
self.data.lock()
}
}
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