use std::cell::UnsafeCell;
use std::ops::{Deref, DerefMut};
use std::fmt;
use raw_rwlock::RawRwLock;
pub struct RwLock<T: ?Sized> {
rwlock: RawRwLock,
data: UnsafeCell<T>,
}
unsafe impl<T: ?Sized + Send> Send for RwLock<T> {}
unsafe impl<T: ?Sized + Send + Sync> Sync for RwLock<T> {}
#[must_use]
pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
rwlock: &'a RawRwLock,
data: &'a T,
}
#[must_use]
pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
rwlock: &'a RawRwLock,
data: &'a mut T,
}
impl<T> RwLock<T> {
#[cfg(feature = "nightly")]
#[inline]
pub const fn new(val: T) -> RwLock<T> {
RwLock {
data: UnsafeCell::new(val),
rwlock: RawRwLock::new(),
}
}
#[cfg(not(feature = "nightly"))]
#[inline]
pub fn new(val: T) -> RwLock<T> {
RwLock {
data: UnsafeCell::new(val),
rwlock: RawRwLock::new(),
}
}
#[inline]
pub fn into_inner(self) -> T {
unsafe { self.data.into_inner() }
}
}
impl<T: ?Sized> RwLock<T> {
#[inline]
pub fn read(&self) -> RwLockReadGuard<T> {
self.rwlock.lock_shared();
RwLockReadGuard {
rwlock: &self.rwlock,
data: unsafe { &*self.data.get() },
}
}
#[inline]
pub fn try_read(&self) -> Option<RwLockReadGuard<T>> {
if self.rwlock.try_lock_shared() {
Some(RwLockReadGuard {
rwlock: &self.rwlock,
data: unsafe { &*self.data.get() },
})
} else {
None
}
}
#[inline]
pub fn write(&self) -> RwLockWriteGuard<T> {
self.rwlock.lock_exclusive();
RwLockWriteGuard {
rwlock: &self.rwlock,
data: unsafe { &mut *self.data.get() },
}
}
#[inline]
pub fn try_write(&self) -> Option<RwLockWriteGuard<T>> {
if self.rwlock.try_lock_exclusive() {
Some(RwLockWriteGuard {
rwlock: &self.rwlock,
data: unsafe { &mut *self.data.get() },
})
} else {
None
}
}
#[inline]
pub fn get_mut(&mut self) -> &mut T {
unsafe { &mut *self.data.get() }
}
}
impl<T: ?Sized + Default> Default for RwLock<T> {
#[inline]
fn default() -> RwLock<T> {
RwLock::new(Default::default())
}
}
impl<T: ?Sized + fmt::Debug> fmt::Debug for RwLock<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.try_read() {
Some(guard) => write!(f, "RwLock {{ data: {:?} }}", &*guard),
None => write!(f, "RwLock {{ <locked> }}"),
}
}
}
impl<'a, T: ?Sized + 'a> Deref for RwLockReadGuard<'a, T> {
type Target = T;
#[inline]
fn deref(&self) -> &T {
self.data
}
}
impl<'a, T: ?Sized + 'a> Drop for RwLockReadGuard<'a, T> {
#[inline]
fn drop(&mut self) {
self.rwlock.unlock_shared();
}
}
impl<'a, T: ?Sized + 'a> Deref for RwLockWriteGuard<'a, T> {
type Target = T;
#[inline]
fn deref(&self) -> &T {
self.data
}
}
impl<'a, T: ?Sized + 'a> DerefMut for RwLockWriteGuard<'a, T> {
#[inline]
fn deref_mut(&mut self) -> &mut T {
self.data
}
}
impl<'a, T: ?Sized + 'a> Drop for RwLockWriteGuard<'a, T> {
#[inline]
fn drop(&mut self) {
self.rwlock.unlock_exclusive();
}
}
#[cfg(test)]
mod tests {
extern crate rand;
use self::rand::Rng;
use std::sync::mpsc::channel;
use std::thread;
use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};
use RwLock;
#[derive(Eq, PartialEq, Debug)]
struct NonCopy(i32);
#[test]
fn smoke() {
let l = RwLock::new(());
drop(l.read());
drop(l.write());
drop((l.read(), l.read()));
drop(l.write());
}
#[test]
fn frob() {
lazy_static! {
static ref R: RwLock<()> = RwLock::new(());
}
const N: u32 = 10;
const M: u32 = 1000;
let (tx, rx) = channel::<()>();
for _ in 0..N {
let tx = tx.clone();
thread::spawn(move || {
let mut rng = rand::thread_rng();
for _ in 0..M {
if rng.gen_weighted_bool(N) {
drop(R.write());
} else {
drop(R.read());
}
}
drop(tx);
});
}
drop(tx);
let _ = rx.recv();
}
#[test]
fn test_rw_arc_no_poison_wr() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _: Result<(), _> = thread::spawn(move || {
let _lock = arc2.write();
panic!();
})
.join();
let lock = arc.read();
assert_eq!(*lock, 1);
}
#[test]
fn test_rw_arc_no_poison_ww() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _: Result<(), _> = thread::spawn(move || {
let _lock = arc2.write();
panic!();
})
.join();
let lock = arc.write();
assert_eq!(*lock, 1);
}
#[test]
fn test_rw_arc_no_poison_rr() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _: Result<(), _> = thread::spawn(move || {
let _lock = arc2.read();
panic!();
})
.join();
let lock = arc.read();
assert_eq!(*lock, 1);
}
#[test]
fn test_rw_arc_no_poison_rw() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _: Result<(), _> = thread::spawn(move || {
let _lock = arc2.read();
panic!()
})
.join();
let lock = arc.write();
assert_eq!(*lock, 1);
}
#[test]
fn test_rw_arc() {
let arc = Arc::new(RwLock::new(0));
let arc2 = arc.clone();
let (tx, rx) = channel();
thread::spawn(move || {
let mut lock = arc2.write();
for _ in 0..10 {
let tmp = *lock;
*lock = -1;
thread::yield_now();
*lock = tmp + 1;
}
tx.send(()).unwrap();
});
let mut children = Vec::new();
for _ in 0..5 {
let arc3 = arc.clone();
children.push(thread::spawn(move || {
let lock = arc3.read();
assert!(*lock >= 0);
}));
}
for r in children {
assert!(r.join().is_ok());
}
rx.recv().unwrap();
let lock = arc.read();
assert_eq!(*lock, 10);
}
#[test]
fn test_rw_arc_access_in_unwind() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _ = thread::spawn(move || -> () {
struct Unwinder {
i: Arc<RwLock<isize>>,
}
impl Drop for Unwinder {
fn drop(&mut self) {
let mut lock = self.i.write();
*lock += 1;
}
}
let _u = Unwinder { i: arc2 };
panic!();
})
.join();
let lock = arc.read();
assert_eq!(*lock, 2);
}
#[test]
fn test_rwlock_unsized() {
let rw: &RwLock<[i32]> = &RwLock::new([1, 2, 3]);
{
let b = &mut *rw.write();
b[0] = 4;
b[2] = 5;
}
let comp: &[i32] = &[4, 2, 5];
assert_eq!(&*rw.read(), comp);
}
#[test]
fn test_rwlock_try_write() {
let lock = RwLock::new(0isize);
let read_guard = lock.read();
let write_result = lock.try_write();
match write_result {
None => (),
Some(_) => {
assert!(false,
"try_write should not succeed while read_guard is in scope")
}
}
drop(read_guard);
}
#[test]
fn test_into_inner() {
let m = RwLock::new(NonCopy(10));
assert_eq!(m.into_inner(), NonCopy(10));
}
#[test]
fn test_into_inner_drop() {
struct Foo(Arc<AtomicUsize>);
impl Drop for Foo {
fn drop(&mut self) {
self.0.fetch_add(1, Ordering::SeqCst);
}
}
let num_drops = Arc::new(AtomicUsize::new(0));
let m = RwLock::new(Foo(num_drops.clone()));
assert_eq!(num_drops.load(Ordering::SeqCst), 0);
{
let _inner = m.into_inner();
assert_eq!(num_drops.load(Ordering::SeqCst), 0);
}
assert_eq!(num_drops.load(Ordering::SeqCst), 1);
}
#[test]
fn test_get_mut() {
let mut m = RwLock::new(NonCopy(10));
*m.get_mut() = NonCopy(20);
assert_eq!(m.into_inner(), NonCopy(20));
}
}