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//! Guardian provides owned mutex guards for refcounted mutexes.
//!
//! Normally, lock guards (be it for `Mutex` or `RwLock`) are bound to the lifetime of the borrow
//! of the underlying lock. Specifically, the function signatures all resemble:
//! `fn lock<'a>(&'a self) -> Guard<'a>`.
//!
//! If the mutex is refcounted using an `Rc` or an `Arc`, it is not necessary for the guard to be
//! scoped in this way -- it could instead carry with it a ref to the mutex in question, which
//! allows the guard to be held for as long as is necessary. This is particularly useful for
//! writing iterators where it is advantageous to hold a read lock for the duration of the
//! iteration.
//!
//! # Poisoning
//!
//! When taking a lock using a guardian, similarly to when taking an `RwLock` or `Mutex`, the
//! result may be poisoned on panics. The poison is propagated from that of the underlying `lock()`
//! method, so for `RwLock`s, the same rule applies for when a lock may be poisioned.
use std::ops::Deref;
use std::ops::DerefMut;
use std::rc;
use std::sync;
// ATTENTION READERS:
// Most of the code looks identical for Arc vs Rc, for RwLockRead vs RwLockWrite, and for Mutex vs
// RwLock. If you change anything for one type, be sure to also make the same changes to the other
// variants below.
//
// Each structure holds the guard in an Option to ensure that we drop the guard before we drop the
// handle, as dropping the guard will access the handle.
// ****************************************************************************
// The basic wrapper types
// ****************************************************************************
/// RAII structure used to release the shared read access of a lock when dropped.
/// Keeps a handle to an `Arc` so that the lock is not dropped until the guard is.
///
/// The data protected by the mutex can be access through this guard via its `Deref` and `DerefMut`
/// implementations.
pub struct ArcRwLockReadGuardian<T: 'static> {
_handle: sync::Arc<sync::RwLock<T>>,
inner: Option<sync::RwLockReadGuard<'static, T>>,
}
/// RAII structure used to release the exclusive write access of a lock when dropped.
/// Keeps a handle to an `Arc` so that the lock is not dropped until the guard is.
///
/// The data protected by the mutex can be access through this guard via its `Deref` and `DerefMut`
/// implementations.
pub struct ArcRwLockWriteGuardian<T: 'static> {
_handle: sync::Arc<sync::RwLock<T>>,
inner: Option<sync::RwLockWriteGuard<'static, T>>,
}
/// An RAII implementation of a "scoped lock" of a mutex. When this structure is dropped (falls out
/// of scope), the lock will be unlocked. Keeps a handle to an `Arc` so that the lock is not
/// dropped until the guard is.
///
/// The data protected by the mutex can be access through this guard via its `Deref` and `DerefMut`
/// implementations.
pub struct ArcMutexGuardian<T: 'static> {
_handle: sync::Arc<sync::Mutex<T>>,
inner: Option<sync::MutexGuard<'static, T>>,
}
/// RAII structure used to release the shared read access of a lock when dropped.
/// Keeps a handle to an `Rc` so that the lock is not dropped until the guard is.
///
/// The data protected by the mutex can be access through this guard via its `Deref` and `DerefMut`
/// implementations.
pub struct RcRwLockReadGuardian<T: 'static> {
_handle: rc::Rc<sync::RwLock<T>>,
inner: Option<sync::RwLockReadGuard<'static, T>>,
}
/// RAII structure used to release the exclusive write access of a lock when dropped.
/// Keeps a handle to an `Rc` so that the lock is not dropped until the guard is.
///
/// The data protected by the mutex can be access through this guard via its `Deref` and `DerefMut`
/// implementations.
pub struct RcRwLockWriteGuardian<T: 'static> {
_handle: rc::Rc<sync::RwLock<T>>,
inner: Option<sync::RwLockWriteGuard<'static, T>>,
}
/// An RAII implementation of a "scoped lock" of a mutex. When this structure is dropped (falls out
/// of scope), the lock will be unlocked. Keeps a handle to an `Rc` so that the lock is not
/// dropped until the guard is.
///
/// The data protected by the mutex can be access through this guard via its `Deref` and `DerefMut`
/// implementations.
pub struct RcMutexGuardian<T: 'static> {
_handle: rc::Rc<sync::Mutex<T>>,
inner: Option<sync::MutexGuard<'static, T>>,
}
// ****************************************************************************
// Traits: Deref
// ****************************************************************************
impl<T> Deref for ArcRwLockReadGuardian<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
self.inner.as_ref().expect("inner is None only in drop")
}
}
impl<T> Deref for ArcRwLockWriteGuardian<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
self.inner.as_ref().expect("inner is None only in drop")
}
}
impl<T> Deref for ArcMutexGuardian<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
self.inner.as_ref().expect("inner is None only in drop")
}
}
impl<T> Deref for RcRwLockReadGuardian<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
self.inner.as_ref().expect("inner is None only in drop")
}
}
impl<T> Deref for RcRwLockWriteGuardian<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
self.inner.as_ref().expect("inner is None only in drop")
}
}
impl<T> Deref for RcMutexGuardian<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
self.inner.as_ref().expect("inner is None only in drop")
}
}
// ****************************************************************************
// Traits: DerefMut
// ****************************************************************************
impl<T> DerefMut for ArcRwLockWriteGuardian<T> {
fn deref_mut(&mut self) -> &mut T {
self.inner.as_mut().expect("inner is None only in drop")
}
}
impl<T> DerefMut for RcRwLockWriteGuardian<T> {
fn deref_mut(&mut self) -> &mut T {
self.inner.as_mut().expect("inner is None only in drop")
}
}
impl<T> DerefMut for ArcMutexGuardian<T> {
fn deref_mut(&mut self) -> &mut T {
self.inner.as_mut().expect("inner is None only in drop")
}
}
impl<T> DerefMut for RcMutexGuardian<T> {
fn deref_mut(&mut self) -> &mut T {
self.inner.as_mut().expect("inner is None only in drop")
}
}
// ****************************************************************************
// Traits: From
// ****************************************************************************
impl<T> From<sync::Arc<sync::RwLock<T>>> for ArcRwLockReadGuardian<T> {
fn from(handle: sync::Arc<sync::RwLock<T>>) -> Self {
ArcRwLockReadGuardian::take(handle).unwrap()
}
}
impl<T> From<sync::Arc<sync::RwLock<T>>> for ArcRwLockWriteGuardian<T> {
fn from(handle: sync::Arc<sync::RwLock<T>>) -> Self {
ArcRwLockWriteGuardian::take(handle).unwrap()
}
}
impl<T> From<sync::Arc<sync::Mutex<T>>> for ArcMutexGuardian<T> {
fn from(handle: sync::Arc<sync::Mutex<T>>) -> Self {
ArcMutexGuardian::take(handle).unwrap()
}
}
impl<T> From<rc::Rc<sync::RwLock<T>>> for RcRwLockReadGuardian<T> {
fn from(handle: rc::Rc<sync::RwLock<T>>) -> Self {
RcRwLockReadGuardian::take(handle).unwrap()
}
}
impl<T> From<rc::Rc<sync::RwLock<T>>> for RcRwLockWriteGuardian<T> {
fn from(handle: rc::Rc<sync::RwLock<T>>) -> Self {
RcRwLockWriteGuardian::take(handle).unwrap()
}
}
impl<T> From<rc::Rc<sync::Mutex<T>>> for RcMutexGuardian<T> {
fn from(handle: rc::Rc<sync::Mutex<T>>) -> Self {
RcMutexGuardian::take(handle).unwrap()
}
}
// ****************************************************************************
// macros
// ****************************************************************************
macro_rules! take {
( $handle: ident, $guard:ty, $guardian:ident, $lfunc:ident ) => {{
use std::mem;
// We want to express that it's safe to keep the read guard around for as long as the
// Arc/Rc is around. Unfortunately, we can't say this directly with lifetimes, because
// we have to move the Arc/Rc below, which Rust doesn't know allows the borrow to
// continue. We therefore transmute to a 'static Guard, and ensure that any borrows we
// expose are bounded by the lifetime of the guardian (which also holds the Arc/Rc).
let lock: sync::LockResult<$guard> = unsafe { mem::transmute($handle.$lfunc()) };
match lock {
Ok(guard) => Ok($guardian {
_handle: $handle,
inner: Some(guard),
}),
Err(guard) => Err(sync::PoisonError::new($guardian {
_handle: $handle,
inner: Some(guard.into_inner()),
})),
}
}};
}
macro_rules! try_take {
( $handle: ident, $guard:ty, $guardian:ident, $lfunc:ident ) => {{
use std::mem;
use std::sync::TryLockError::{Poisoned, WouldBlock};
// Safe following the same reasoning as in take!.
let lock: sync::TryLockResult<$guard> = unsafe { mem::transmute($handle.$lfunc()) };
match lock {
Ok(guard) => Some(Ok($guardian {
_handle: $handle,
inner: Some(guard),
})),
Err(WouldBlock) => None,
Err(Poisoned(guard)) => Some(Err(sync::PoisonError::new($guardian {
_handle: $handle,
inner: Some(guard.into_inner()),
}))),
}
}};
}
// ****************************************************************************
// impl
// ****************************************************************************
impl<T> ArcRwLockReadGuardian<T> {
/// Locks the given rwlock with shared read access, blocking the current thread until it can be
/// acquired.
///
/// The calling thread will be blocked until there are no more writers which hold the lock.
/// There may be other readers currently inside the lock when this method returns. This method
/// does not provide any guarantees with respect to the ordering of whether contentious readers
/// or writers will acquire the lock first.
///
/// Returns an RAII guardian which will release this thread's shared access once it is dropped.
/// The guardian also holds a strong reference to the lock's `Arc`, which is dropped when the
/// guard is.
pub fn take(handle: sync::Arc<sync::RwLock<T>>) -> sync::LockResult<ArcRwLockReadGuardian<T>> {
take!(
handle,
sync::RwLockReadGuard<'static, T>,
ArcRwLockReadGuardian,
read
)
}
/// Attempts to acquire this rwlock with shared read access.
///
/// If the access could not be granted at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned which will release the shared access when it is dropped.
/// The guardian also holds a strong reference to the lock's `Arc`, which is dropped when the
/// guard is.
///
/// This function does not block.
///
/// This function does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.
pub fn try_take(
handle: sync::Arc<sync::RwLock<T>>,
) -> Option<sync::LockResult<ArcRwLockReadGuardian<T>>> {
try_take!(
handle,
sync::RwLockReadGuard<'static, T>,
ArcRwLockReadGuardian,
try_read
)
}
}
impl<T> ArcRwLockWriteGuardian<T> {
/// Locks this rwlock with exclusive write access, blocking the current thread until it can be
/// acquired.
///
/// This function will not return while other writers or other readers currently have access to
/// the lock.
///
/// Returns an RAII guard which will drop the write access of this rwlock when dropped.
/// The guardian also holds a strong reference to the lock's `Arc`, which is dropped when the
/// guard is.
///
/// # Errors
///
/// This function will return an error if the `RwLock` is poisoned. An `RwLock` is poisoned
/// whenever a writer panics while holding an exclusive lock. An error will be returned when
/// the lock is acquired.
pub fn take(handle: sync::Arc<sync::RwLock<T>>) -> sync::LockResult<ArcRwLockWriteGuardian<T>> {
take!(
handle,
sync::RwLockWriteGuard<'static, T>,
ArcRwLockWriteGuardian,
write
)
}
/// Attempts to lock this rwlock with exclusive write access.
///
/// If the access could not be granted at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned, which will drop the write access of this rwlock when dropped.
/// The guardian also holds a strong reference to the lock's `Arc`, which is dropped when the
/// guard is.
///
/// This function does not block.
///
/// This function does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.
pub fn try_take(
handle: sync::Arc<sync::RwLock<T>>,
) -> Option<sync::LockResult<ArcRwLockWriteGuardian<T>>> {
try_take!(
handle,
sync::RwLockWriteGuard<'static, T>,
ArcRwLockWriteGuardian,
try_write
)
}
}
impl<T> ArcMutexGuardian<T> {
/// Acquires a mutex, blocking the current thread until it is able to do so.
///
/// This function will block the local thread until it is available to acquire the mutex. Upon
/// returning, the thread is the only thread with the mutex held. An RAII guardian is returned
/// to allow scoped unlock of the lock. When the guard goes out of scope, the mutex will be
/// unlocked. The guardian also holds a strong reference to the lock's `Arc`, which is dropped
/// when the guard is.
///
/// # Errors
///
/// If another user of this mutex panicked while holding the mutex, then this call will return
/// an error once the mutex is acquired.
pub fn take(handle: sync::Arc<sync::Mutex<T>>) -> sync::LockResult<ArcMutexGuardian<T>> {
take!(handle, sync::MutexGuard<'static, T>, ArcMutexGuardian, lock)
}
/// Attempts to acquire this lock.
///
/// If the lock could not be acquired at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned. The lock will be unlocked when the guard is dropped.
/// The guardian also holds a strong reference to the lock's `Arc`, which is dropped
/// when the guard is.
///
/// This function does not block.
pub fn try_take(
handle: sync::Arc<sync::Mutex<T>>,
) -> Option<sync::LockResult<ArcMutexGuardian<T>>> {
try_take!(
handle,
sync::MutexGuard<'static, T>,
ArcMutexGuardian,
try_lock
)
}
}
// And this is all the same as above, but with s/Arc/Rc/
impl<T> RcRwLockReadGuardian<T> {
/// Locks the given rwlock with shared read access, blocking the current thread until it can be
/// acquired.
///
/// The calling thread will be blocked until there are no more writers which hold the lock.
/// There may be other readers currently inside the lock when this method returns. This method
/// does not provide any guarantees with respect to the ordering of whether contentious readers
/// or writers will acquire the lock first.
///
/// Returns an RAII guardian which will release this thread's shared access once it is dropped.
/// The guardian also holds a strong reference to the lock's `Rc`, which is dropped when the
/// guard is.
pub fn take(handle: rc::Rc<sync::RwLock<T>>) -> sync::LockResult<RcRwLockReadGuardian<T>> {
take!(
handle,
sync::RwLockReadGuard<'static, T>,
RcRwLockReadGuardian,
read
)
}
/// Attempts to acquire this rwlock with shared read access.
///
/// If the access could not be granted at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned which will release the shared access when it is dropped.
/// The guardian also holds a strong reference to the lock's `Rc`, which is dropped when the
/// guard is.
///
/// This function does not block.
///
/// This function does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.
pub fn try_take(
handle: rc::Rc<sync::RwLock<T>>,
) -> Option<sync::LockResult<RcRwLockReadGuardian<T>>> {
try_take!(
handle,
sync::RwLockReadGuard<'static, T>,
RcRwLockReadGuardian,
try_read
)
}
}
impl<T> RcRwLockWriteGuardian<T> {
/// Locks this rwlock with exclusive write access, blocking the current thread until it can be
/// acquired.
///
/// This function will not return while other writers or other readers currently have access to
/// the lock.
///
/// Returns an RAII guard which will drop the write access of this rwlock when dropped.
/// The guardian also holds a strong reference to the lock's `Rc`, which is dropped when the
/// guard is.
///
/// # Errors
///
/// This function will return an error if the `RwLock` is poisoned. An `RwLock` is poisoned
/// whenever a writer panics while holding an exclusive lock. An error will be returned when
/// the lock is acquired.
pub fn take(handle: rc::Rc<sync::RwLock<T>>) -> sync::LockResult<RcRwLockWriteGuardian<T>> {
take!(
handle,
sync::RwLockWriteGuard<'static, T>,
RcRwLockWriteGuardian,
write
)
}
/// Attempts to lock this rwlock with exclusive write access.
///
/// If the access could not be granted at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned, which will drop the write access of this rwlock when dropped.
/// The guardian also holds a strong reference to the lock's `Rc`, which is dropped when the
/// guard is.
///
/// This function does not block.
///
/// This function does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.
pub fn try_take(
handle: rc::Rc<sync::RwLock<T>>,
) -> Option<sync::LockResult<RcRwLockWriteGuardian<T>>> {
try_take!(
handle,
sync::RwLockWriteGuard<'static, T>,
RcRwLockWriteGuardian,
try_write
)
}
}
impl<T> RcMutexGuardian<T> {
/// Acquires a mutex, blocking the current thread until it is able to do so.
///
/// This function will block the local thread until it is available to acquire the mutex. Upon
/// returning, the thread is the only thread with the mutex held. An RAII guardian is returned
/// to allow scoped unlock of the lock. When the guard goes out of scope, the mutex will be
/// unlocked. The guardian also holds a strong reference to the lock's `Rc`, which is dropped
/// when the guard is.
///
/// # Errors
///
/// If another user of this mutex panicked while holding the mutex, then this call will return
/// an error once the mutex is acquired.
pub fn take(handle: rc::Rc<sync::Mutex<T>>) -> sync::LockResult<RcMutexGuardian<T>> {
take!(handle, sync::MutexGuard<'static, T>, RcMutexGuardian, lock)
}
/// Attempts to acquire this lock.
///
/// If the lock could not be acquired at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned. The lock will be unlocked when the guard is dropped.
/// The guardian also holds a strong reference to the lock's `Rc`, which is dropped
/// when the guard is.
///
/// This function does not block.
pub fn try_take(
handle: rc::Rc<sync::Mutex<T>>,
) -> Option<sync::LockResult<RcMutexGuardian<T>>> {
try_take!(
handle,
sync::MutexGuard<'static, T>,
RcMutexGuardian,
try_lock
)
}
}
// ****************************************************************************
// Drop
// ****************************************************************************
impl<T> Drop for ArcRwLockReadGuardian<T> {
fn drop(&mut self) {
self.inner.take();
}
}
impl<T> Drop for ArcRwLockWriteGuardian<T> {
fn drop(&mut self) {
self.inner.take();
}
}
impl<T> Drop for ArcMutexGuardian<T> {
fn drop(&mut self) {
self.inner.take();
}
}
impl<T> Drop for RcRwLockReadGuardian<T> {
fn drop(&mut self) {
self.inner.take();
}
}
impl<T> Drop for RcRwLockWriteGuardian<T> {
fn drop(&mut self) {
self.inner.take();
}
}
impl<T> Drop for RcMutexGuardian<T> {
fn drop(&mut self) {
self.inner.take();
}
}
// ****************************************************************************
// And finally all the tests
// ****************************************************************************
#[cfg(test)]
mod tests {
use super::*;
use std::rc;
use std::sync;
#[test]
fn arc_rw_read() {
let base = sync::Arc::new(sync::RwLock::new(true));
// the use of scopes below is necessary so that we can drop base at the end.
// otherwise, all the x1's (i.e., base.read()) would hold on to borrows.
// this is part of the problem that Guardian is trying to solve.
let x2 = {
let x1 = base.read().unwrap();
let x2 = ArcRwLockReadGuardian::take(base.clone()).unwrap();
// guardian dereferences correctly
assert_eq!(&*x1, &*x2);
// guardian holds read lock
drop(x1);
assert!(base.try_write().is_err(), "guardian holds read lock");
x2
};
{
// guardian can be moved
let x1 = base.read().unwrap();
let x2_ = x2;
assert_eq!(&*x1, &*x2_);
// moving guardian does not release lock
drop(x1);
assert!(base.try_write().is_err(), "guardian still holds read lock");
// dropping guardian drops read lock
drop(x2_);
assert!(base.try_write().is_ok(), "guardian drops read lock");
}
// guardian works even after all other Arcs have been dropped
let x = ArcRwLockReadGuardian::take(base).unwrap();
assert_eq!(&*x, &true);
}
#[test]
fn arc_rw_write() {
let base = sync::Arc::new(sync::RwLock::new(true));
let mut x = ArcRwLockWriteGuardian::take(base.clone()).unwrap();
// guardian dereferences correctly
assert_eq!(&*x, &true);
// guardian can write
*x = false;
assert_eq!(&*x, &false);
// guardian holds write lock
assert!(base.try_read().is_err(), "guardian holds write lock");
// guardian can be moved
let x_ = x;
assert_eq!(&*x_, &false);
// moving guardian does not release lock
assert!(base.try_read().is_err(), "guardian still holds write lock");
// dropping guardian drops write lock
drop(x_);
assert!(base.try_read().is_ok(), "guardian drops write lock");
// guardian works even after all other Arcs have been dropped
let x = ArcRwLockWriteGuardian::take(base).unwrap();
assert_eq!(&*x, &false);
}
#[test]
fn arc_rw_try() {
let base = sync::Arc::new(sync::RwLock::new(true));
let mut x = ArcRwLockWriteGuardian::try_take(base.clone())
.unwrap()
.unwrap();
// guardian dereferences correctly
assert_eq!(&*x, &true);
// guardian can write
*x = false;
assert_eq!(&*x, &false);
// guardian holds write lock
assert!(base.try_read().is_err(), "guardian holds write lock");
// guardian can be moved
let x_ = x;
assert_eq!(&*x_, &false);
// moving guardian does not release lock
assert!(base.try_read().is_err(), "guardian still holds write lock");
// try_take returns None if it would block
assert!(ArcRwLockWriteGuardian::try_take(base.clone()).is_none());
assert!(ArcRwLockReadGuardian::try_take(base.clone()).is_none());
// dropping guardian drops write lock
drop(x_);
assert!(base.try_read().is_ok(), "guardian drops write lock");
// guardian works even after all other Arcs have been dropped
let x = ArcRwLockWriteGuardian::take(base).unwrap();
assert_eq!(&*x, &false);
}
#[test]
fn arc_mu() {
let base = sync::Arc::new(sync::Mutex::new(true));
let mut x = ArcMutexGuardian::take(base.clone()).unwrap();
// guardian dereferences correctly
assert_eq!(&*x, &true);
// guardian can write
*x = false;
assert_eq!(&*x, &false);
// guardian holds lock
assert!(base.try_lock().is_err(), "guardian holds lock");
// guardian can be moved
let x_ = x;
assert_eq!(&*x_, &false);
// moving guardian does not release lock
assert!(base.try_lock().is_err(), "guardian still holds lock");
// dropping guardian drops lock
drop(x_);
assert!(base.try_lock().is_ok(), "guardian drops lock");
// guardian works even after all other Arcs have been dropped
let x = ArcMutexGuardian::take(base).unwrap();
assert_eq!(&*x, &false);
}
#[test]
fn arc_mu_try() {
let base = sync::Arc::new(sync::Mutex::new(true));
let mut x = ArcMutexGuardian::try_take(base.clone()).unwrap().unwrap();
// guardian dereferences correctly
assert_eq!(&*x, &true);
// guardian can write
*x = false;
assert_eq!(&*x, &false);
// guardian holds lock
assert!(base.try_lock().is_err(), "guardian holds lock");
// guardian can be moved
let x_ = x;
assert_eq!(&*x_, &false);
// moving guardian does not release lock
assert!(base.try_lock().is_err(), "guardian still holds lock");
// try_take returns None if it would block
assert!(ArcMutexGuardian::try_take(base.clone()).is_none());
// dropping guardian drops lock
drop(x_);
assert!(base.try_lock().is_ok(), "guardian drops lock");
// guardian works even after all other Arcs have been dropped
let x = ArcMutexGuardian::take(base).unwrap();
assert_eq!(&*x, &false);
}
#[test]
fn rc_rw_read() {
let base = rc::Rc::new(sync::RwLock::new(true));
// the use of scopes below is necessary so that we can drop base at the end.
// otherwise, all the x1's (i.e., base.read()) would hold on to borrows.
// this is part of the problem that Guardian is trying to solve.
let x2 = {
let x1 = base.read().unwrap();
let x2 = RcRwLockReadGuardian::take(base.clone()).unwrap();
// guardian dereferences correctly
assert_eq!(&*x1, &*x2);
// guardian holds read lock
drop(x1);
assert!(base.try_write().is_err(), "guardian holds read lock");
x2
};
{
// guardian can be moved
let x1 = base.read().unwrap();
let x2_ = x2;
assert_eq!(&*x1, &*x2_);
// moving guardian does not release lock
drop(x1);
assert!(base.try_write().is_err(), "guardian still holds read lock");
// dropping guardian drops read lock
drop(x2_);
assert!(base.try_write().is_ok(), "guardian drops read lock");
}
// guardian works even after all other Rcs have been dropped
let x = RcRwLockReadGuardian::take(base).unwrap();
assert_eq!(&*x, &true);
}
#[test]
fn rc_rw_write() {
let base = rc::Rc::new(sync::RwLock::new(true));
let mut x = RcRwLockWriteGuardian::take(base.clone()).unwrap();
// guardian dereferences correctly
assert_eq!(&*x, &true);
// guardian can write
*x = false;
assert_eq!(&*x, &false);
// guardian holds write lock
assert!(base.try_read().is_err(), "guardian holds write lock");
// guardian can be moved
let x_ = x;
assert_eq!(&*x_, &false);
// moving guardian does not release lock
assert!(base.try_read().is_err(), "guardian still holds write lock");
// dropping guardian drops write lock
drop(x_);
assert!(base.try_read().is_ok(), "guardian drops write lock");
// guardian works even after all other Rcs have been dropped
let x = RcRwLockWriteGuardian::take(base).unwrap();
assert_eq!(&*x, &false);
}
#[test]
fn rc_rw_try() {
let base = rc::Rc::new(sync::RwLock::new(true));
let mut x = RcRwLockWriteGuardian::try_take(base.clone())
.unwrap()
.unwrap();
// guardian dereferences correctly
assert_eq!(&*x, &true);
// guardian can write
*x = false;
assert_eq!(&*x, &false);
// guardian holds write lock
assert!(base.try_read().is_err(), "guardian holds write lock");
// guardian can be moved
let x_ = x;
assert_eq!(&*x_, &false);
// moving guardian does not release lock
assert!(base.try_read().is_err(), "guardian still holds write lock");
// try_take returns None if it would block
assert!(RcRwLockWriteGuardian::try_take(base.clone()).is_none());
assert!(RcRwLockReadGuardian::try_take(base.clone()).is_none());
// dropping guardian drops write lock
drop(x_);
assert!(base.try_read().is_ok(), "guardian drops write lock");
// guardian works even after all other Rcs have been dropped
let x = RcRwLockWriteGuardian::take(base).unwrap();
assert_eq!(&*x, &false);
}
#[test]
fn rc_mu() {
let base = rc::Rc::new(sync::Mutex::new(true));
let mut x = RcMutexGuardian::take(base.clone()).unwrap();
// guardian dereferences correctly
assert_eq!(&*x, &true);
// guardian can write
*x = false;
assert_eq!(&*x, &false);
// guardian holds lock
assert!(base.try_lock().is_err(), "guardian holds lock");
// guardian can be moved
let x_ = x;
assert_eq!(&*x_, &false);
// moving guardian does not release lock
assert!(base.try_lock().is_err(), "guardian still holds lock");
// dropping guardian drops lock
drop(x_);
assert!(base.try_lock().is_ok(), "guardian drops lock");
// guardian works even after all other Rcs have been dropped
let x = RcMutexGuardian::take(base).unwrap();
assert_eq!(&*x, &false);
}
#[test]
fn rc_mu_try() {
let base = rc::Rc::new(sync::Mutex::new(true));
let mut x = RcMutexGuardian::take(base.clone()).unwrap();
// guardian dereferences correctly
assert_eq!(&*x, &true);
// guardian can write
*x = false;
assert_eq!(&*x, &false);
// guardian holds lock
assert!(base.try_lock().is_err(), "guardian holds lock");
// guardian can be moved
let x_ = x;
assert_eq!(&*x_, &false);
// moving guardian does not release lock
assert!(base.try_lock().is_err(), "guardian still holds lock");
// try_take returns None if it would block
assert!(RcMutexGuardian::try_take(base.clone()).is_none());
// dropping guardian drops lock
drop(x_);
assert!(base.try_lock().is_ok(), "guardian drops lock");
// guardian works even after all other Rcs have been dropped
let x = RcMutexGuardian::take(base).unwrap();
assert_eq!(&*x, &false);
}
}