library/std/src/sync/condvar.rs - toolchain/rustc - Git at Google

 #[cfg(test)]
 mod tests;

 use crate::fmt;
 use crate::sync::{LockResult, MutexGuard, PoisonError, mutex, poison};
 use crate::sys::sync as sys;
 use crate::time::{Duration, Instant};

 /// A type indicating whether a timed wait on a condition variable returned
 /// due to a time out or not.
 ///
 /// It is returned by the [`wait_timeout`] method.
 ///
 /// [`wait_timeout`]: Condvar::wait_timeout
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 #[stable(feature = "wait_timeout", since = "1.5.0")]
 pub struct WaitTimeoutResult(bool);

 impl WaitTimeoutResult {
     /// Returns `true` if the wait was known to have timed out.
     ///
     /// # Examples
     ///
     /// This example spawns a thread which will sleep 20 milliseconds before
     /// updating a boolean value and then notifying the condvar.
     ///
     /// The main thread will wait with a 10 millisecond timeout on the condvar
     /// and will leave the loop upon timeout.
     ///
     /// ```
     /// use std::sync::{Arc, Condvar, Mutex};
     /// use std::thread;
     /// use std::time::Duration;
     ///
     /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
     /// let pair2 = Arc::clone(&pair);
     ///
     /// # let handle =
     /// thread::spawn(move || {
     ///     let (lock, cvar) = &*pair2;
     ///
     ///     // Let's wait 20 milliseconds before notifying the condvar.
     ///     thread::sleep(Duration::from_millis(20));
     ///
     ///     let mut started = lock.lock().unwrap();
     ///     // We update the boolean value.
     ///     *started = true;
     ///     cvar.notify_one();
     /// });
     ///
     /// // Wait for the thread to start up.
     /// let (lock, cvar) = &*pair;
     /// loop {
     ///     // Let's put a timeout on the condvar's wait.
     ///     let result = cvar.wait_timeout(lock.lock().unwrap(), Duration::from_millis(10)).unwrap();
     ///     // 10 milliseconds have passed.
     ///     if result.1.timed_out() {
     ///         // timed out now and we can leave.
     ///         break
     ///     }
     /// }
     /// # // Prevent leaks for Miri.
     /// # let _ = handle.join();
     /// ```
     #[must_use]
     #[stable(feature = "wait_timeout", since = "1.5.0")]
     pub fn timed_out(&self) -> bool {
         self.0
     }
 }

 /// A Condition Variable
 ///
 /// Condition variables represent the ability to block a thread such that it
 /// consumes no CPU time while waiting for an event to occur. Condition
 /// variables are typically associated with a boolean predicate (a condition)
 /// and a mutex. The predicate is always verified inside of the mutex before
 /// determining that a thread must block.
 ///
 /// Functions in this module will block the current **thread** of execution.
 /// Note that any attempt to use multiple mutexes on the same condition
 /// variable may result in a runtime panic.
 ///
 /// # Examples
 ///
 /// ```
 /// use std::sync::{Arc, Mutex, Condvar};
 /// use std::thread;
 ///
 /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
 /// let pair2 = Arc::clone(&pair);
 ///
 /// // Inside of our lock, spawn a new thread, and then wait for it to start.
 /// thread::spawn(move || {
 ///     let (lock, cvar) = &*pair2;
 ///     let mut started = lock.lock().unwrap();
 ///     *started = true;
 ///     // We notify the condvar that the value has changed.
 ///     cvar.notify_one();
 /// });
 ///
 /// // Wait for the thread to start up.
 /// let (lock, cvar) = &*pair;
 /// let mut started = lock.lock().unwrap();
 /// while !*started {
 ///     started = cvar.wait(started).unwrap();
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Condvar {
     inner: sys::Condvar,
 }

 impl Condvar {
     /// Creates a new condition variable which is ready to be waited on and
     /// notified.
     ///
     /// # Examples
     ///
     /// ```
     /// use std::sync::Condvar;
     ///
     /// let condvar = Condvar::new();
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
     #[must_use]
     #[inline]
     pub const fn new() -> Condvar {
         Condvar { inner: sys::Condvar::new() }
     }

     /// Blocks the current thread until this condition variable receives a
     /// notification.
     ///
     /// This function will atomically unlock the mutex specified (represented by
     /// `guard`) and block the current thread. This means that any calls
     /// to [`notify_one`] or [`notify_all`] which happen logically after the
     /// mutex is unlocked are candidates to wake this thread up. When this
     /// function call returns, the lock specified will have been re-acquired.
     ///
     /// Note that this function is susceptible to spurious wakeups. Condition
     /// variables normally have a boolean predicate associated with them, and
     /// the predicate must always be checked each time this function returns to
     /// protect against spurious wakeups.
     ///
     /// # Errors
     ///
     /// This function will return an error if the mutex being waited on is
     /// poisoned when this thread re-acquires the lock. For more information,
     /// see information about [poisoning] on the [`Mutex`] type.
     ///
     /// # Panics
     ///
     /// This function may [`panic!`] if it is used with more than one mutex
     /// over time.
     ///
     /// [`notify_one`]: Self::notify_one
     /// [`notify_all`]: Self::notify_all
     /// [poisoning]: super::Mutex#poisoning
     /// [`Mutex`]: super::Mutex
     ///
     /// # Examples
     ///
     /// ```
     /// use std::sync::{Arc, Mutex, Condvar};
     /// use std::thread;
     ///
     /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
     /// let pair2 = Arc::clone(&pair);
     ///
     /// thread::spawn(move || {
     ///     let (lock, cvar) = &*pair2;
     ///     let mut started = lock.lock().unwrap();
     ///     *started = true;
     ///     // We notify the condvar that the value has changed.
     ///     cvar.notify_one();
     /// });
     ///
     /// // Wait for the thread to start up.
     /// let (lock, cvar) = &*pair;
     /// let mut started = lock.lock().unwrap();
     /// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
     /// while !*started {
     ///     started = cvar.wait(started).unwrap();
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn wait<'a, T>(&self, guard: MutexGuard<'a, T>) -> LockResult<MutexGuard<'a, T>> {
         let poisoned = unsafe {
             let lock = mutex::guard_lock(&guard);
             self.inner.wait(lock);
             mutex::guard_poison(&guard).get()
         };
         if poisoned { Err(PoisonError::new(guard)) } else { Ok(guard) }
     }

     /// Blocks the current thread until the provided condition becomes false.
     ///
     /// `condition` is checked immediately; if not met (returns `true`), this
     /// will [`wait`] for the next notification then check again. This repeats
     /// until `condition` returns `false`, in which case this function returns.
     ///
     /// This function will atomically unlock the mutex specified (represented by
     /// `guard`) and block the current thread. This means that any calls
     /// to [`notify_one`] or [`notify_all`] which happen logically after the
     /// mutex is unlocked are candidates to wake this thread up. When this
     /// function call returns, the lock specified will have been re-acquired.
     ///
     /// # Errors
     ///
     /// This function will return an error if the mutex being waited on is
     /// poisoned when this thread re-acquires the lock. For more information,
     /// see information about [poisoning] on the [`Mutex`] type.
     ///
     /// [`wait`]: Self::wait
     /// [`notify_one`]: Self::notify_one
     /// [`notify_all`]: Self::notify_all
     /// [poisoning]: super::Mutex#poisoning
     /// [`Mutex`]: super::Mutex
     ///
     /// # Examples
     ///
     /// ```
     /// use std::sync::{Arc, Mutex, Condvar};
     /// use std::thread;
     ///
     /// let pair = Arc::new((Mutex::new(true), Condvar::new()));
     /// let pair2 = Arc::clone(&pair);
     ///
     /// thread::spawn(move || {
     ///     let (lock, cvar) = &*pair2;
     ///     let mut pending = lock.lock().unwrap();
     ///     *pending = false;
     ///     // We notify the condvar that the value has changed.
     ///     cvar.notify_one();
     /// });
     ///
     /// // Wait for the thread to start up.
     /// let (lock, cvar) = &*pair;
     /// // As long as the value inside the `Mutex<bool>` is `true`, we wait.
     /// let _guard = cvar.wait_while(lock.lock().unwrap(), |pending| { *pending }).unwrap();
     /// ```
     #[stable(feature = "wait_until", since = "1.42.0")]
     pub fn wait_while<'a, T, F>(
         &self,
         mut guard: MutexGuard<'a, T>,
         mut condition: F,
     ) -> LockResult<MutexGuard<'a, T>>
     where
         F: FnMut(&mut T) -> bool,
     {
         while condition(&mut *guard) {
             guard = self.wait(guard)?;
         }
         Ok(guard)
     }

     /// Waits on this condition variable for a notification, timing out after a
     /// specified duration.
     ///
     /// The semantics of this function are equivalent to [`wait`]
     /// except that the thread will be blocked for roughly no longer
     /// than `ms` milliseconds. This method should not be used for
     /// precise timing due to anomalies such as preemption or platform
     /// differences that might not cause the maximum amount of time
     /// waited to be precisely `ms`.
     ///
     /// Note that the best effort is made to ensure that the time waited is
     /// measured with a monotonic clock, and not affected by the changes made to
     /// the system time.
     ///
     /// The returned boolean is `false` only if the timeout is known
     /// to have elapsed.
     ///
     /// Like [`wait`], the lock specified will be re-acquired when this function
     /// returns, regardless of whether the timeout elapsed or not.
     ///
     /// [`wait`]: Self::wait
     ///
     /// # Examples
     ///
     /// ```
     /// use std::sync::{Arc, Mutex, Condvar};
     /// use std::thread;
     ///
     /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
     /// let pair2 = Arc::clone(&pair);
     ///
     /// thread::spawn(move || {
     ///     let (lock, cvar) = &*pair2;
     ///     let mut started = lock.lock().unwrap();
     ///     *started = true;
     ///     // We notify the condvar that the value has changed.
     ///     cvar.notify_one();
     /// });
     ///
     /// // Wait for the thread to start up.
     /// let (lock, cvar) = &*pair;
     /// let mut started = lock.lock().unwrap();
     /// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
     /// loop {
     ///     let result = cvar.wait_timeout_ms(started, 10).unwrap();
     ///     // 10 milliseconds have passed, or maybe the value changed!
     ///     started = result.0;
     ///     if *started == true {
     ///         // We received the notification and the value has been updated, we can leave.
     ///         break
     ///     }
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[deprecated(since = "1.6.0", note = "replaced by `std::sync::Condvar::wait_timeout`")]
     pub fn wait_timeout_ms<'a, T>(
         &self,
         guard: MutexGuard<'a, T>,
         ms: u32,
     ) -> LockResult<(MutexGuard<'a, T>, bool)> {
         let res = self.wait_timeout(guard, Duration::from_millis(ms as u64));
         poison::map_result(res, |(a, b)| (a, !b.timed_out()))
     }

     /// Waits on this condition variable for a notification, timing out after a
     /// specified duration.
     ///
     /// The semantics of this function are equivalent to [`wait`] except that
     /// the thread will be blocked for roughly no longer than `dur`. This
     /// method should not be used for precise timing due to anomalies such as
     /// preemption or platform differences that might not cause the maximum
     /// amount of time waited to be precisely `dur`.
     ///
     /// Note that the best effort is made to ensure that the time waited is
     /// measured with a monotonic clock, and not affected by the changes made to
     /// the system time. This function is susceptible to spurious wakeups.
     /// Condition variables normally have a boolean predicate associated with
     /// them, and the predicate must always be checked each time this function
     /// returns to protect against spurious wakeups. Additionally, it is
     /// typically desirable for the timeout to not exceed some duration in
     /// spite of spurious wakes, thus the sleep-duration is decremented by the
     /// amount slept. Alternatively, use the `wait_timeout_while` method
     /// to wait with a timeout while a predicate is true.
     ///
     /// The returned [`WaitTimeoutResult`] value indicates if the timeout is
     /// known to have elapsed.
     ///
     /// Like [`wait`], the lock specified will be re-acquired when this function
     /// returns, regardless of whether the timeout elapsed or not.
     ///
     /// [`wait`]: Self::wait
     /// [`wait_timeout_while`]: Self::wait_timeout_while
     ///
     /// # Examples
     ///
     /// ```
     /// use std::sync::{Arc, Mutex, Condvar};
     /// use std::thread;
     /// use std::time::Duration;
     ///
     /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
     /// let pair2 = Arc::clone(&pair);
     ///
     /// thread::spawn(move || {
     ///     let (lock, cvar) = &*pair2;
     ///     let mut started = lock.lock().unwrap();
     ///     *started = true;
     ///     // We notify the condvar that the value has changed.
     ///     cvar.notify_one();
     /// });
     ///
     /// // wait for the thread to start up
     /// let (lock, cvar) = &*pair;
     /// let mut started = lock.lock().unwrap();
     /// // as long as the value inside the `Mutex<bool>` is `false`, we wait
     /// loop {
     ///     let result = cvar.wait_timeout(started, Duration::from_millis(10)).unwrap();
     ///     // 10 milliseconds have passed, or maybe the value changed!
     ///     started = result.0;
     ///     if *started == true {
     ///         // We received the notification and the value has been updated, we can leave.
     ///         break
     ///     }
     /// }
     /// ```
     #[stable(feature = "wait_timeout", since = "1.5.0")]
     pub fn wait_timeout<'a, T>(
         &self,
         guard: MutexGuard<'a, T>,
         dur: Duration,
     ) -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> {
         let (poisoned, result) = unsafe {
             let lock = mutex::guard_lock(&guard);
             let success = self.inner.wait_timeout(lock, dur);
             (mutex::guard_poison(&guard).get(), WaitTimeoutResult(!success))
         };
         if poisoned { Err(PoisonError::new((guard, result))) } else { Ok((guard, result)) }
     }

     /// Waits on this condition variable for a notification, timing out after a
     /// specified duration.
     ///
     /// The semantics of this function are equivalent to [`wait_while`] except
     /// that the thread will be blocked for roughly no longer than `dur`. This
     /// method should not be used for precise timing due to anomalies such as
     /// preemption or platform differences that might not cause the maximum
     /// amount of time waited to be precisely `dur`.
     ///
     /// Note that the best effort is made to ensure that the time waited is
     /// measured with a monotonic clock, and not affected by the changes made to
     /// the system time.
     ///
     /// The returned [`WaitTimeoutResult`] value indicates if the timeout is
     /// known to have elapsed without the condition being met.
     ///
     /// Like [`wait_while`], the lock specified will be re-acquired when this
     /// function returns, regardless of whether the timeout elapsed or not.
     ///
     /// [`wait_while`]: Self::wait_while
     /// [`wait_timeout`]: Self::wait_timeout
     ///
     /// # Examples
     ///
     /// ```
     /// use std::sync::{Arc, Mutex, Condvar};
     /// use std::thread;
     /// use std::time::Duration;
     ///
     /// let pair = Arc::new((Mutex::new(true), Condvar::new()));
     /// let pair2 = Arc::clone(&pair);
     ///
     /// thread::spawn(move || {
     ///     let (lock, cvar) = &*pair2;
     ///     let mut pending = lock.lock().unwrap();
     ///     *pending = false;
     ///     // We notify the condvar that the value has changed.
     ///     cvar.notify_one();
     /// });
     ///
     /// // wait for the thread to start up
     /// let (lock, cvar) = &*pair;
     /// let result = cvar.wait_timeout_while(
     ///     lock.lock().unwrap(),
     ///     Duration::from_millis(100),
     ///     |&mut pending| pending,
     /// ).unwrap();
     /// if result.1.timed_out() {
     ///     // timed-out without the condition ever evaluating to false.
     /// }
     /// // access the locked mutex via result.0
     /// ```
     #[stable(feature = "wait_timeout_until", since = "1.42.0")]
     pub fn wait_timeout_while<'a, T, F>(
         &self,
         mut guard: MutexGuard<'a, T>,
         dur: Duration,
         mut condition: F,
     ) -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)>
     where
         F: FnMut(&mut T) -> bool,
     {
         let start = Instant::now();
         loop {
             if !condition(&mut *guard) {
                 return Ok((guard, WaitTimeoutResult(false)));
             }
             let timeout = match dur.checked_sub(start.elapsed()) {
                 Some(timeout) => timeout,
                 None => return Ok((guard, WaitTimeoutResult(true))),
             };
             guard = self.wait_timeout(guard, timeout)?.0;
         }
     }

     /// Wakes up one blocked thread on this condvar.
     ///
     /// If there is a blocked thread on this condition variable, then it will
     /// be woken up from its call to [`wait`] or [`wait_timeout`]. Calls to
     /// `notify_one` are not buffered in any way.
     ///
     /// To wake up all threads, see [`notify_all`].
     ///
     /// [`wait`]: Self::wait
     /// [`wait_timeout`]: Self::wait_timeout
     /// [`notify_all`]: Self::notify_all
     ///
     /// # Examples
     ///
     /// ```
     /// use std::sync::{Arc, Mutex, Condvar};
     /// use std::thread;
     ///
     /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
     /// let pair2 = Arc::clone(&pair);
     ///
     /// thread::spawn(move || {
     ///     let (lock, cvar) = &*pair2;
     ///     let mut started = lock.lock().unwrap();
     ///     *started = true;
     ///     // We notify the condvar that the value has changed.
     ///     cvar.notify_one();
     /// });
     ///
     /// // Wait for the thread to start up.
     /// let (lock, cvar) = &*pair;
     /// let mut started = lock.lock().unwrap();
     /// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
     /// while !*started {
     ///     started = cvar.wait(started).unwrap();
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn notify_one(&self) {
         self.inner.notify_one()
     }

     /// Wakes up all blocked threads on this condvar.
     ///
     /// This method will ensure that any current waiters on the condition
     /// variable are awoken. Calls to `notify_all()` are not buffered in any
     /// way.
     ///
     /// To wake up only one thread, see [`notify_one`].
     ///
     /// [`notify_one`]: Self::notify_one
     ///
     /// # Examples
     ///
     /// ```
     /// use std::sync::{Arc, Mutex, Condvar};
     /// use std::thread;
     ///
     /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
     /// let pair2 = Arc::clone(&pair);
     ///
     /// thread::spawn(move || {
     ///     let (lock, cvar) = &*pair2;
     ///     let mut started = lock.lock().unwrap();
     ///     *started = true;
     ///     // We notify the condvar that the value has changed.
     ///     cvar.notify_all();
     /// });
     ///
     /// // Wait for the thread to start up.
     /// let (lock, cvar) = &*pair;
     /// let mut started = lock.lock().unwrap();
     /// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
     /// while !*started {
     ///     started = cvar.wait(started).unwrap();
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn notify_all(&self) {
         self.inner.notify_all()
     }
 }

 #[stable(feature = "std_debug", since = "1.16.0")]
 impl fmt::Debug for Condvar {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("Condvar").finish_non_exhaustive()
     }
 }

 #[stable(feature = "condvar_default", since = "1.10.0")]
 impl Default for Condvar {
     /// Creates a `Condvar` which is ready to be waited on and notified.
     fn default() -> Condvar {
         Condvar::new()
     }
 }
	#[cfg(test)]
	mod tests;

	use crate::fmt;
	use crate::sync::{LockResult, MutexGuard, PoisonError, mutex, poison};
	use crate::sys::sync as sys;
	use crate::time::{Duration, Instant};

	/// A type indicating whether a timed wait on a condition variable returned
	/// due to a time out or not.
	///
	/// It is returned by the [`wait_timeout`] method.
	///
	/// [`wait_timeout`]: Condvar::wait_timeout
	#[derive(Debug, PartialEq, Eq, Copy, Clone)]
	#[stable(feature = "wait_timeout", since = "1.5.0")]
	pub struct WaitTimeoutResult(bool);

	impl WaitTimeoutResult {
	/// Returns `true` if the wait was known to have timed out.
	///
	/// # Examples
	///
	/// This example spawns a thread which will sleep 20 milliseconds before
	/// updating a boolean value and then notifying the condvar.
	///
	/// The main thread will wait with a 10 millisecond timeout on the condvar
	/// and will leave the loop upon timeout.
	///
	/// ```
	/// use std::sync::{Arc, Condvar, Mutex};
	/// use std::thread;
	/// use std::time::Duration;
	///
	/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// # let handle =
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	///
	/// // Let's wait 20 milliseconds before notifying the condvar.
	/// thread::sleep(Duration::from_millis(20));
	///
	/// let mut started = lock.lock().unwrap();
	/// // We update the boolean value.
	/// *started = true;
	/// cvar.notify_one();
	/// });
	///
	/// // Wait for the thread to start up.
	/// let (lock, cvar) = &*pair;
	/// loop {
	/// // Let's put a timeout on the condvar's wait.
	/// let result = cvar.wait_timeout(lock.lock().unwrap(), Duration::from_millis(10)).unwrap();
	/// // 10 milliseconds have passed.
	/// if result.1.timed_out() {
	/// // timed out now and we can leave.
	/// break
	/// }
	/// }
	/// # // Prevent leaks for Miri.
	/// # let _ = handle.join();
	/// ```
	#[must_use]
	#[stable(feature = "wait_timeout", since = "1.5.0")]
	pub fn timed_out(&self) -> bool {
	self.0
	}
	}

	/// A Condition Variable
	///
	/// Condition variables represent the ability to block a thread such that it
	/// consumes no CPU time while waiting for an event to occur. Condition
	/// variables are typically associated with a boolean predicate (a condition)
	/// and a mutex. The predicate is always verified inside of the mutex before
	/// determining that a thread must block.
	///
	/// Functions in this module will block the current thread of execution.
	/// Note that any attempt to use multiple mutexes on the same condition
	/// variable may result in a runtime panic.
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::{Arc, Mutex, Condvar};
	/// use std::thread;
	///
	/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// // Inside of our lock, spawn a new thread, and then wait for it to start.
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	/// let mut started = lock.lock().unwrap();
	/// *started = true;
	/// // We notify the condvar that the value has changed.
	/// cvar.notify_one();
	/// });
	///
	/// // Wait for the thread to start up.
	/// let (lock, cvar) = &*pair;
	/// let mut started = lock.lock().unwrap();
	/// while !*started {
	/// started = cvar.wait(started).unwrap();
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	pub struct Condvar {
	inner: sys::Condvar,
	}

	impl Condvar {
	/// Creates a new condition variable which is ready to be waited on and
	/// notified.
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::Condvar;
	///
	/// let condvar = Condvar::new();
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	#[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
	#[must_use]
	#[inline]
	pub const fn new() -> Condvar {
	Condvar { inner: sys::Condvar::new() }
	}

	/// Blocks the current thread until this condition variable receives a
	/// notification.
	///
	/// This function will atomically unlock the mutex specified (represented by
	/// `guard`) and block the current thread. This means that any calls
	/// to [`notify_one`] or [`notify_all`] which happen logically after the
	/// mutex is unlocked are candidates to wake this thread up. When this
	/// function call returns, the lock specified will have been re-acquired.
	///
	/// Note that this function is susceptible to spurious wakeups. Condition
	/// variables normally have a boolean predicate associated with them, and
	/// the predicate must always be checked each time this function returns to
	/// protect against spurious wakeups.
	///
	/// # Errors
	///
	/// This function will return an error if the mutex being waited on is
	/// poisoned when this thread re-acquires the lock. For more information,
	/// see information about [poisoning] on the [`Mutex`] type.
	///
	/// # Panics
	///
	/// This function may [`panic!`] if it is used with more than one mutex
	/// over time.
	///
	/// [`notify_one`]: Self::notify_one
	/// [`notify_all`]: Self::notify_all
	/// [poisoning]: super::Mutex#poisoning
	/// [`Mutex`]: super::Mutex
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::{Arc, Mutex, Condvar};
	/// use std::thread;
	///
	/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	/// let mut started = lock.lock().unwrap();
	/// *started = true;
	/// // We notify the condvar that the value has changed.
	/// cvar.notify_one();
	/// });
	///
	/// // Wait for the thread to start up.
	/// let (lock, cvar) = &*pair;
	/// let mut started = lock.lock().unwrap();
	/// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
	/// while !*started {
	/// started = cvar.wait(started).unwrap();
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	pub fn wait<'a, T>(&self, guard: MutexGuard<'a, T>) -> LockResult<MutexGuard<'a, T>> {
	let poisoned = unsafe {
	let lock = mutex::guard_lock(&guard);
	self.inner.wait(lock);
	mutex::guard_poison(&guard).get()
	};
	if poisoned { Err(PoisonError::new(guard)) } else { Ok(guard) }
	}

	/// Blocks the current thread until the provided condition becomes false.
	///
	/// `condition` is checked immediately; if not met (returns `true`), this
	/// will [`wait`] for the next notification then check again. This repeats
	/// until `condition` returns `false`, in which case this function returns.
	///
	/// This function will atomically unlock the mutex specified (represented by
	/// `guard`) and block the current thread. This means that any calls
	/// to [`notify_one`] or [`notify_all`] which happen logically after the
	/// mutex is unlocked are candidates to wake this thread up. When this
	/// function call returns, the lock specified will have been re-acquired.
	///
	/// # Errors
	///
	/// This function will return an error if the mutex being waited on is
	/// poisoned when this thread re-acquires the lock. For more information,
	/// see information about [poisoning] on the [`Mutex`] type.
	///
	/// [`wait`]: Self::wait
	/// [`notify_one`]: Self::notify_one
	/// [`notify_all`]: Self::notify_all
	/// [poisoning]: super::Mutex#poisoning
	/// [`Mutex`]: super::Mutex
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::{Arc, Mutex, Condvar};
	/// use std::thread;
	///
	/// let pair = Arc::new((Mutex::new(true), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	/// let mut pending = lock.lock().unwrap();
	/// *pending = false;
	/// // We notify the condvar that the value has changed.
	/// cvar.notify_one();
	/// });
	///
	/// // Wait for the thread to start up.
	/// let (lock, cvar) = &*pair;
	/// // As long as the value inside the `Mutex<bool>` is `true`, we wait.
	/// let _guard = cvar.wait_while(lock.lock().unwrap(), \|pending\| { *pending }).unwrap();
	/// ```
	#[stable(feature = "wait_until", since = "1.42.0")]
	pub fn wait_while<'a, T, F>(
	&self,
	mut guard: MutexGuard<'a, T>,
	mut condition: F,
	) -> LockResult<MutexGuard<'a, T>>
	where
	F: FnMut(&mut T) -> bool,
	{
	while condition(&mut *guard) {
	guard = self.wait(guard)?;
	}
	Ok(guard)
	}

	/// Waits on this condition variable for a notification, timing out after a
	/// specified duration.
	///
	/// The semantics of this function are equivalent to [`wait`]
	/// except that the thread will be blocked for roughly no longer
	/// than `ms` milliseconds. This method should not be used for
	/// precise timing due to anomalies such as preemption or platform
	/// differences that might not cause the maximum amount of time
	/// waited to be precisely `ms`.
	///
	/// Note that the best effort is made to ensure that the time waited is
	/// measured with a monotonic clock, and not affected by the changes made to
	/// the system time.
	///
	/// The returned boolean is `false` only if the timeout is known
	/// to have elapsed.
	///
	/// Like [`wait`], the lock specified will be re-acquired when this function
	/// returns, regardless of whether the timeout elapsed or not.
	///
	/// [`wait`]: Self::wait
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::{Arc, Mutex, Condvar};
	/// use std::thread;
	///
	/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	/// let mut started = lock.lock().unwrap();
	/// *started = true;
	/// // We notify the condvar that the value has changed.
	/// cvar.notify_one();
	/// });
	///
	/// // Wait for the thread to start up.
	/// let (lock, cvar) = &*pair;
	/// let mut started = lock.lock().unwrap();
	/// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
	/// loop {
	/// let result = cvar.wait_timeout_ms(started, 10).unwrap();
	/// // 10 milliseconds have passed, or maybe the value changed!
	/// started = result.0;
	/// if *started == true {
	/// // We received the notification and the value has been updated, we can leave.
	/// break
	/// }
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	#[deprecated(since = "1.6.0", note = "replaced by `std::sync::Condvar::wait_timeout`")]
	pub fn wait_timeout_ms<'a, T>(
	&self,
	guard: MutexGuard<'a, T>,
	ms: u32,
	) -> LockResult<(MutexGuard<'a, T>, bool)> {
	let res = self.wait_timeout(guard, Duration::from_millis(ms as u64));
	poison::map_result(res, \|(a, b)\| (a, !b.timed_out()))
	}

	/// Waits on this condition variable for a notification, timing out after a
	/// specified duration.
	///
	/// The semantics of this function are equivalent to [`wait`] except that
	/// the thread will be blocked for roughly no longer than `dur`. This
	/// method should not be used for precise timing due to anomalies such as
	/// preemption or platform differences that might not cause the maximum
	/// amount of time waited to be precisely `dur`.
	///
	/// Note that the best effort is made to ensure that the time waited is
	/// measured with a monotonic clock, and not affected by the changes made to
	/// the system time. This function is susceptible to spurious wakeups.
	/// Condition variables normally have a boolean predicate associated with
	/// them, and the predicate must always be checked each time this function
	/// returns to protect against spurious wakeups. Additionally, it is
	/// typically desirable for the timeout to not exceed some duration in
	/// spite of spurious wakes, thus the sleep-duration is decremented by the
	/// amount slept. Alternatively, use the `wait_timeout_while` method
	/// to wait with a timeout while a predicate is true.
	///
	/// The returned [`WaitTimeoutResult`] value indicates if the timeout is
	/// known to have elapsed.
	///
	/// Like [`wait`], the lock specified will be re-acquired when this function
	/// returns, regardless of whether the timeout elapsed or not.
	///
	/// [`wait`]: Self::wait
	/// [`wait_timeout_while`]: Self::wait_timeout_while
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::{Arc, Mutex, Condvar};
	/// use std::thread;
	/// use std::time::Duration;
	///
	/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	/// let mut started = lock.lock().unwrap();
	/// *started = true;
	/// // We notify the condvar that the value has changed.
	/// cvar.notify_one();
	/// });
	///
	/// // wait for the thread to start up
	/// let (lock, cvar) = &*pair;
	/// let mut started = lock.lock().unwrap();
	/// // as long as the value inside the `Mutex<bool>` is `false`, we wait
	/// loop {
	/// let result = cvar.wait_timeout(started, Duration::from_millis(10)).unwrap();
	/// // 10 milliseconds have passed, or maybe the value changed!
	/// started = result.0;
	/// if *started == true {
	/// // We received the notification and the value has been updated, we can leave.
	/// break
	/// }
	/// }
	/// ```
	#[stable(feature = "wait_timeout", since = "1.5.0")]
	pub fn wait_timeout<'a, T>(
	&self,
	guard: MutexGuard<'a, T>,
	dur: Duration,
	) -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> {
	let (poisoned, result) = unsafe {
	let lock = mutex::guard_lock(&guard);
	let success = self.inner.wait_timeout(lock, dur);
	(mutex::guard_poison(&guard).get(), WaitTimeoutResult(!success))
	};
	if poisoned { Err(PoisonError::new((guard, result))) } else { Ok((guard, result)) }
	}

	/// Waits on this condition variable for a notification, timing out after a
	/// specified duration.
	///
	/// The semantics of this function are equivalent to [`wait_while`] except
	/// that the thread will be blocked for roughly no longer than `dur`. This
	/// method should not be used for precise timing due to anomalies such as
	/// preemption or platform differences that might not cause the maximum
	/// amount of time waited to be precisely `dur`.
	///
	/// Note that the best effort is made to ensure that the time waited is
	/// measured with a monotonic clock, and not affected by the changes made to
	/// the system time.
	///
	/// The returned [`WaitTimeoutResult`] value indicates if the timeout is
	/// known to have elapsed without the condition being met.
	///
	/// Like [`wait_while`], the lock specified will be re-acquired when this
	/// function returns, regardless of whether the timeout elapsed or not.
	///
	/// [`wait_while`]: Self::wait_while
	/// [`wait_timeout`]: Self::wait_timeout
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::{Arc, Mutex, Condvar};
	/// use std::thread;
	/// use std::time::Duration;
	///
	/// let pair = Arc::new((Mutex::new(true), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	/// let mut pending = lock.lock().unwrap();
	/// *pending = false;
	/// // We notify the condvar that the value has changed.
	/// cvar.notify_one();
	/// });
	///
	/// // wait for the thread to start up
	/// let (lock, cvar) = &*pair;
	/// let result = cvar.wait_timeout_while(
	/// lock.lock().unwrap(),
	/// Duration::from_millis(100),
	/// \|&mut pending\| pending,
	/// ).unwrap();
	/// if result.1.timed_out() {
	/// // timed-out without the condition ever evaluating to false.
	/// }
	/// // access the locked mutex via result.0
	/// ```
	#[stable(feature = "wait_timeout_until", since = "1.42.0")]
	pub fn wait_timeout_while<'a, T, F>(
	&self,
	mut guard: MutexGuard<'a, T>,
	dur: Duration,
	mut condition: F,
	) -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)>
	where
	F: FnMut(&mut T) -> bool,
	{
	let start = Instant::now();
	loop {
	if !condition(&mut *guard) {
	return Ok((guard, WaitTimeoutResult(false)));
	}
	let timeout = match dur.checked_sub(start.elapsed()) {
	Some(timeout) => timeout,
	None => return Ok((guard, WaitTimeoutResult(true))),
	};
	guard = self.wait_timeout(guard, timeout)?.0;
	}
	}

	/// Wakes up one blocked thread on this condvar.
	///
	/// If there is a blocked thread on this condition variable, then it will
	/// be woken up from its call to [`wait`] or [`wait_timeout`]. Calls to
	/// `notify_one` are not buffered in any way.
	///
	/// To wake up all threads, see [`notify_all`].
	///
	/// [`wait`]: Self::wait
	/// [`wait_timeout`]: Self::wait_timeout
	/// [`notify_all`]: Self::notify_all
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::{Arc, Mutex, Condvar};
	/// use std::thread;
	///
	/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	/// let mut started = lock.lock().unwrap();
	/// *started = true;
	/// // We notify the condvar that the value has changed.
	/// cvar.notify_one();
	/// });
	///
	/// // Wait for the thread to start up.
	/// let (lock, cvar) = &*pair;
	/// let mut started = lock.lock().unwrap();
	/// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
	/// while !*started {
	/// started = cvar.wait(started).unwrap();
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	pub fn notify_one(&self) {
	self.inner.notify_one()
	}

	/// Wakes up all blocked threads on this condvar.
	///
	/// This method will ensure that any current waiters on the condition
	/// variable are awoken. Calls to `notify_all()` are not buffered in any
	/// way.
	///
	/// To wake up only one thread, see [`notify_one`].
	///
	/// [`notify_one`]: Self::notify_one
	///
	/// # Examples
	///
	/// ```
	/// use std::sync::{Arc, Mutex, Condvar};
	/// use std::thread;
	///
	/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
	/// let pair2 = Arc::clone(&pair);
	///
	/// thread::spawn(move \|\| {
	/// let (lock, cvar) = &*pair2;
	/// let mut started = lock.lock().unwrap();
	/// *started = true;
	/// // We notify the condvar that the value has changed.
	/// cvar.notify_all();
	/// });
	///
	/// // Wait for the thread to start up.
	/// let (lock, cvar) = &*pair;
	/// let mut started = lock.lock().unwrap();
	/// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
	/// while !*started {
	/// started = cvar.wait(started).unwrap();
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	pub fn notify_all(&self) {
	self.inner.notify_all()
	}
	}

	#[stable(feature = "std_debug", since = "1.16.0")]
	impl fmt::Debug for Condvar {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	f.debug_struct("Condvar").finish_non_exhaustive()
	}
	}

	#[stable(feature = "condvar_default", since = "1.10.0")]
	impl Default for Condvar {
	/// Creates a `Condvar` which is ready to be waited on and notified.
	fn default() -> Condvar {
	Condvar::new()
	}
	}