Struct Condvar 

pub struct Condvar<C> { /* private fields */ }

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 thread must block.

Implementations

impl<C: RawCondvar> Condvar<C>

pub const fn new() -> Condvar<C>

Creates a new condition variable which is ready to be waited on and notified.

pub fn raw(&self) -> &C

Returns the underlying raw condvar object.

Note that you will most likely need to import the RawCondvar trait from lock_api to be able to call functions on the raw condvar.

pub fn notify_one(&self) -> bool

Wakes up one blocked thread on this condvar.

Returns whether a thread was woken up.

If there is a blocked thread on this condition variable, then it will be woken up from its call to wait or wait_timeout.

To wake up all threads, see notify_all().

pub fn notify_all(&self) -> usize

Wakes up all blocked threads on this condvar.

Returns the number of threads woken up.

This method will ensure that any current waiters on the condition variable are awoken.

To wake up only one thread, see notify_one().

pub fn wait<T: ?Sized>(&self, mutex_guard: &mut MutexGuard<'_, C::RawMutex, T>)

Blocks the current thread until this condition variable receives a notification.

This function will unlock the mutex specified (represented by mutex_guard) and block the current thread. This means that any calls to notify_*() 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.

Panics

The underlying RawCondvar implementation provided by C is permitted to panic if requested to wait on two distinct MutexGuards simultaneously.

pub fn wait_while<T, F>( &self, mutex_guard: &mut MutexGuard<'_, C::RawMutex, T>, condition: F, )

where T: ?Sized, F: FnMut(&mut T) -> bool,

Blocks the current thread until this condition variable receives a notification. If the provided condition evaluates to false, then the thread is no longer blocked and the operation is completed. If the condition evaluates to true, then the thread is blocked again and waits for another notification before repeating this process.

This function will unlock the mutex specified (represented by mutex_guard) and block the current thread. This means that any calls to notify_*() 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.

Panics

The underlying RawCondvar implementation provided by C is permitted to panic if requested to wait on two distinct MutexGuards simultaneously.

impl<R: RawMutexTimed, C: RawCondvarTimed<RawMutex = R>> Condvar<C>

pub fn wait_until<T: ?Sized>( &self, mutex_guard: &mut MutexGuard<'_, C::RawMutex, T>, timeout: <C::RawMutex as RawMutexTimed>::Instant, ) -> WaitTimeoutResult

Waits on this condition variable for a notification, timing out after the specified time instant.

The semantics of this function are equivalent to wait() except that the thread will be blocked roughly until timeout is reached. This method should not be used for precise timing due to anomalies such as preemption or platform differences that may not cause the maximum amount of time waited to be precisely timeout.

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.

Like wait, the lock specified will be re-acquired when this function returns, regardless of whether the timeout elapsed or not.

Panics

The underlying RawCondvar implementation provided by C is permitted to panic if requested to wait on two distinct MutexGuards simultaneously.

pub fn wait_for<T: ?Sized>( &self, mutex_guard: &mut MutexGuard<'_, C::RawMutex, T>, timeout: <C::RawMutex as RawMutexTimed>::Duration, ) -> WaitTimeoutResult

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 timeout. This method should not be used for precise timing due to anomalies such as preemption or platform differences that may not cause the maximum amount of time waited to be precisely timeout.

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.

Like wait, the lock specified will be re-acquired when this function returns, regardless of whether the timeout elapsed or not.

Panics

The underlying RawCondvar implementation provided by C is permitted to panic if requested to wait on two distinct MutexGuards simultaneously.

pub fn wait_while_until<T, F>( &self, mutex_guard: &mut MutexGuard<'_, C::RawMutex, T>, condition: F, timeout: <C::RawMutex as RawMutexTimed>::Instant, ) -> WaitTimeoutResult

where T: ?Sized, F: FnMut(&mut T) -> bool,

Waits on this condition variable for a notification, timing out after the specified time instant. If the provided condition evaluates to false, then the thread is no longer blocked and the operation is completed. If the condition evaluates to true, then the thread is blocked again and waits for another notification before repeating this process.

The semantics of this function are equivalent to wait() except that the thread will be blocked roughly until timeout is reached. This method should not be used for precise timing due to anomalies such as preemption or platform differences that may not cause the maximum amount of time waited to be precisely timeout.

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.

Like wait, the lock specified will be re-acquired when this function returns, regardless of whether the timeout elapsed or not.

Panics

The underlying RawCondvar implementation provided by C is permitted to panic if requested to wait on two distinct MutexGuards simultaneously.

pub fn wait_while_for<T: ?Sized, F>( &self, mutex_guard: &mut MutexGuard<'_, C::RawMutex, T>, condition: F, timeout: <C::RawMutex as RawMutexTimed>::Duration, ) -> WaitTimeoutResult

where F: FnMut(&mut T) -> bool,

Waits on this condition variable for a notification, timing out after a specified duration. If the provided condition evaluates to false, then the thread is no longer blocked and the operation is completed. If the condition evaluates to true, then the thread is blocked again and waits for another notification before repeating this process.

The semantics of this function are equivalent to wait() except that the thread will be blocked for roughly no longer than timeout. This method should not be used for precise timing due to anomalies such as preemption or platform differences that may not cause the maximum amount of time waited to be precisely timeout.

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.

Like wait, the lock specified will be re-acquired when this function returns, regardless of whether the timeout elapsed or not.

Panics

The underlying RawCondvar implementation provided by C is permitted to panic if requested to wait on two distinct MutexGuards simultaneously.

Trait Implementations

impl<C> Debug for Condvar<C>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<C: RawCondvar> Default for Condvar<C>

fn default() -> Condvar<C>

Returns the “default value” for a type.