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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. use sys::mutex as imp; /// An OS-based mutual exclusion lock. /// /// This is the thinnest cross-platform wrapper around OS mutexes. All usage of /// this mutex is unsafe and it is recommended to instead use the safe wrapper /// at the top level of the crate instead of this type. pub struct Mutex(imp::Mutex); unsafe impl Sync for Mutex {} impl Mutex { /// 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, until `init` is called, behavior is undefined if this /// mutex is ever used reentrantly, i.e., `raw_lock` or `try_lock` /// are called by the thread currently holding the lock. pub const fn new() -> Mutex { Mutex(imp::Mutex::new()) } /// Prepare the mutex for use. /// /// This should be called once the mutex is at a stable memory address. /// If called, this must be the very first thing that happens to the mutex. /// Calling it in parallel with or after any operation (including another /// `init()`) is undefined behavior. #[inline] pub unsafe fn init(&mut self) { self.0.init() } /// Locks the mutex blocking the current thread until it is available. /// /// Behavior is undefined if the mutex has been moved between this and any /// previous function call. #[inline] pub unsafe fn raw_lock(&self) { self.0.lock() } /// Calls raw_lock() and then returns an RAII guard to guarantee the mutex /// will be unlocked. #[inline] pub unsafe fn lock(&self) -> MutexGuard { self.raw_lock(); MutexGuard(&self.0) } /// Attempts to lock the mutex without blocking, returning whether it was /// successfully acquired or not. /// /// Behavior is undefined if the mutex has been moved between this and any /// previous function call. #[inline] pub unsafe fn try_lock(&self) -> bool { self.0.try_lock() } /// Unlocks the mutex. /// /// Behavior is undefined if the current thread does not actually hold the /// mutex. /// /// Consider switching from the pair of raw_lock() and raw_unlock() to /// lock() whenever possible. #[inline] pub unsafe fn raw_unlock(&self) { self.0.unlock() } /// Deallocates all resources associated with this mutex. /// /// Behavior is undefined if there are current or will be future users of /// this mutex. #[inline] pub unsafe fn destroy(&self) { self.0.destroy() } } // not meant to be exported to the outside world, just the containing module pub fn raw(mutex: &Mutex) -> &imp::Mutex { &mutex.0 } #[must_use] /// A simple RAII utility for the above Mutex without the poisoning semantics. pub struct MutexGuard<'a>(&'a imp::Mutex); impl<'a> Drop for MutexGuard<'a> { #[inline] fn drop(&mut self) { unsafe { self.0.unlock(); } } }