1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use sys::mutex as imp;
13 /// An OS-based mutual exclusion lock.
15 /// This is the thinnest cross-platform wrapper around OS mutexes. All usage of
16 /// this mutex is unsafe and it is recommended to instead use the safe wrapper
17 /// at the top level of the crate instead of this type.
18 pub struct Mutex(imp::Mutex);
20 unsafe impl Sync for Mutex {}
23 /// Creates a new mutex for use.
25 /// Behavior is undefined if the mutex is moved after it is
26 /// first used with any of the functions below.
27 /// Also, until `init` is called, behavior is undefined if this
28 /// mutex is ever used reentrantly, i.e., `raw_lock` or `try_lock`
29 /// are called by the thread currently holding the lock.
30 pub const fn new() -> Mutex { Mutex(imp::Mutex::new()) }
32 /// Prepare the mutex for use.
34 /// This should be called once the mutex is at a stable memory address.
35 /// If called, this must be the very first thing that happens to the mutex.
36 /// Calling it in parallel with or after any operation (including another
37 /// `init()`) is undefined behavior.
39 pub unsafe fn init(&mut self) { self.0.init() }
41 /// Locks the mutex blocking the current thread until it is available.
43 /// Behavior is undefined if the mutex has been moved between this and any
44 /// previous function call.
46 pub unsafe fn raw_lock(&self) { self.0.lock() }
48 /// Calls raw_lock() and then returns an RAII guard to guarantee the mutex
51 pub unsafe fn lock(&self) -> MutexGuard {
56 /// Attempts to lock the mutex without blocking, returning whether it was
57 /// successfully acquired or not.
59 /// Behavior is undefined if the mutex has been moved between this and any
60 /// previous function call.
62 pub unsafe fn try_lock(&self) -> bool { self.0.try_lock() }
64 /// Unlocks the mutex.
66 /// Behavior is undefined if the current thread does not actually hold the
69 /// Consider switching from the pair of raw_lock() and raw_unlock() to
70 /// lock() whenever possible.
72 pub unsafe fn raw_unlock(&self) { self.0.unlock() }
74 /// Deallocates all resources associated with this mutex.
76 /// Behavior is undefined if there are current or will be future users of
79 pub unsafe fn destroy(&self) { self.0.destroy() }
82 // not meant to be exported to the outside world, just the containing module
83 pub fn raw(mutex: &Mutex) -> &imp::Mutex { &mutex.0 }
86 /// A simple RAII utility for the above Mutex without the poisoning semantics.
87 pub struct MutexGuard<'a>(&'a imp::Mutex);
89 impl<'a> Drop for MutexGuard<'a> {
92 unsafe { self.0.unlock(); }