Rust wrapper for libctru
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// Copyright 2015 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 fmt;
use marker;
use ops::Deref;
use sys_common::poison::{self, TryLockError, TryLockResult, LockResult};
use sys::mutex as sys;
use panic::{UnwindSafe, RefUnwindSafe};
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/// A re-entrant mutual exclusion
///
/// This mutex will block *other* threads waiting for the lock to become
/// available. The thread which has already locked the mutex can lock it
/// multiple times without blocking, preventing a common source of deadlocks.
pub struct ReentrantMutex<T> {
inner: Box<sys::ReentrantMutex>,
poison: poison::Flag,
data: T,
}
unsafe impl<T: Send> Send for ReentrantMutex<T> {}
unsafe impl<T: Send> Sync for ReentrantMutex<T> {}
impl<T> UnwindSafe for ReentrantMutex<T> {}
impl<T> RefUnwindSafe for ReentrantMutex<T> {}
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/// An RAII implementation of a "scoped lock" of a mutex. When this structure is
/// dropped (falls out of scope), the lock will be unlocked.
///
/// The data protected by the mutex can be accessed through this guard via its
/// Deref implementation.
///
/// # Mutability
///
/// Unlike `MutexGuard`, `ReentrantMutexGuard` does not implement `DerefMut`,
/// because implementation of the trait would violate Rust’s reference aliasing
/// rules. Use interior mutability (usually `RefCell`) in order to mutate the
/// guarded data.
#[must_use = "if unused the ReentrantMutex will immediately unlock"]
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pub struct ReentrantMutexGuard<'a, T: 'a> {
// funny underscores due to how Deref currently works (it disregards field
// privacy).
__lock: &'a ReentrantMutex<T>,
__poison: poison::Guard,
}
impl<'a, T> !marker::Send for ReentrantMutexGuard<'a, T> {}
impl<T> ReentrantMutex<T> {
/// Creates a new reentrant mutex in an unlocked state.
pub fn new(t: T) -> ReentrantMutex<T> {
unsafe {
let mut mutex = ReentrantMutex {
inner: box sys::ReentrantMutex::uninitialized(),
poison: poison::Flag::new(),
data: t,
};
mutex.inner.init();
mutex
}
}
/// Acquires a mutex, blocking the current thread until it is able to do so.
///
/// This function will block the caller until it is available to acquire the mutex.
/// Upon returning, the thread is the only thread with the mutex held. When the thread
/// calling this method already holds the lock, the call shall succeed without
/// blocking.
///
/// # Errors
///
/// If another user of this mutex panicked while holding the mutex, then
/// this call will return failure if the mutex would otherwise be
/// acquired.
pub fn lock(&self) -> LockResult<ReentrantMutexGuard<T>> {
unsafe { self.inner.lock() }
ReentrantMutexGuard::new(&self)
}
/// Attempts to acquire this lock.
///
/// If the lock could not be acquired at this time, then `Err` is returned.
/// Otherwise, an RAII guard is returned.
///
/// This function does not block.
///
/// # Errors
///
/// If another user of this mutex panicked while holding the mutex, then
/// this call will return failure if the mutex would otherwise be
/// acquired.
pub fn try_lock(&self) -> TryLockResult<ReentrantMutexGuard<T>> {
if unsafe { self.inner.try_lock() } {
Ok(ReentrantMutexGuard::new(&self)?)
} else {
Err(TryLockError::WouldBlock)
}
}
}
impl<T> Drop for ReentrantMutex<T> {
fn drop(&mut self) {
// This is actually safe b/c we know that there is no further usage of
// this mutex (it's up to the user to arrange for a mutex to get
// dropped, that's not our job)
unsafe { self.inner.destroy() }
}
}
impl<T: fmt::Debug + 'static> fmt::Debug for ReentrantMutex<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.try_lock() {
Ok(guard) => f.debug_struct("ReentrantMutex").field("data", &*guard).finish(),
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Err(TryLockError::Poisoned(err)) => {
f.debug_struct("ReentrantMutex").field("data", &**err.get_ref()).finish()
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},
Err(TryLockError::WouldBlock) => {
struct LockedPlaceholder;
impl fmt::Debug for LockedPlaceholder {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.write_str("<locked>") }
}
f.debug_struct("ReentrantMutex").field("data", &LockedPlaceholder).finish()
}
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}
}
}
impl<'mutex, T> ReentrantMutexGuard<'mutex, T> {
fn new(lock: &'mutex ReentrantMutex<T>)
-> LockResult<ReentrantMutexGuard<'mutex, T>> {
poison::map_result(lock.poison.borrow(), |guard| {
ReentrantMutexGuard {
__lock: lock,
__poison: guard,
}
})
}
}
impl<'mutex, T> Deref for ReentrantMutexGuard<'mutex, T> {
type Target = T;
fn deref(&self) -> &T {
&self.__lock.data
}
}
impl<'a, T> Drop for ReentrantMutexGuard<'a, T> {
#[inline]
fn drop(&mut self) {
unsafe {
self.__lock.poison.done(&self.__poison);
self.__lock.inner.unlock();
}
}
}
#[cfg(all(test, not(target_os = "emscripten")))]
mod tests {
use sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
use cell::RefCell;
use sync::Arc;
use thread;
#[test]
fn smoke() {
let m = ReentrantMutex::new(());
{
let a = m.lock().unwrap();
{
let b = m.lock().unwrap();
{
let c = m.lock().unwrap();
assert_eq!(*c, ());
}
assert_eq!(*b, ());
}
assert_eq!(*a, ());
}
}
#[test]
fn is_mutex() {
let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
let m2 = m.clone();
let lock = m.lock().unwrap();
let child = thread::spawn(move || {
let lock = m2.lock().unwrap();
assert_eq!(*lock.borrow(), 4950);
});
for i in 0..100 {
let lock = m.lock().unwrap();
*lock.borrow_mut() += i;
}
drop(lock);
child.join().unwrap();
}
#[test]
fn trylock_works() {
let m = Arc::new(ReentrantMutex::new(()));
let m2 = m.clone();
let _lock = m.try_lock().unwrap();
let _lock2 = m.try_lock().unwrap();
thread::spawn(move || {
let lock = m2.try_lock();
assert!(lock.is_err());
}).join().unwrap();
let _lock3 = m.try_lock().unwrap();
}
pub struct Answer<'a>(pub ReentrantMutexGuard<'a, RefCell<u32>>);
impl<'a> Drop for Answer<'a> {
fn drop(&mut self) {
*self.0.borrow_mut() = 42;
}
}
#[test]
fn poison_works() {
let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
let mc = m.clone();
let result = thread::spawn(move ||{
let lock = mc.lock().unwrap();
*lock.borrow_mut() = 1;
let lock2 = mc.lock().unwrap();
*lock.borrow_mut() = 2;
let _answer = Answer(lock2);
panic!("What the answer to my lifetimes dilemma is?");
}).join();
assert!(result.is_err());
let r = m.lock().err().unwrap().into_inner();
assert_eq!(*r.borrow(), 42);
}
}