Struct RwLockReadGuard

#[must_use = "if unused the RwLock will immediately unlock"]
pub struct RwLockReadGuard<'a, R: RawRwLock, T: ?Sized> { /* private fields */ }

RAII structure used to release the shared read access of a lock when dropped.

Implementations

impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> RwLockReadGuard<'a, R, T>

fn rwlock(s: &Self) -> &'a RwLock<R, T>

Returns a reference to the original reader-writer lock object.

fn map<U: ?Sized, F>(s: Self, f: F) -> MappedRwLockReadGuard<'a, R, U>
where
    F: FnOnce(&T) -> &U,

Make a new MappedRwLockReadGuard for a component of the locked data.

This operation cannot fail as the RwLockReadGuard passed in already locked the data.

This is an associated function that needs to be used as RwLockReadGuard::map(...). A method would interfere with methods of the same name on the contents of the locked data.

fn try_map<U: ?Sized, F>(s: Self, f: F) -> Result<MappedRwLockReadGuard<'a, R, U>, Self>
where
    F: FnOnce(&T) -> Option<&U>,

Attempts to make a new MappedRwLockReadGuard for a component of the locked data. Returns the original guard if the closure returns None.

This operation cannot fail as the RwLockReadGuard passed in already locked the data.

This is an associated function that needs to be used as RwLockReadGuard::try_map(...). A method would interfere with methods of the same name on the contents of the locked data.

fn try_map_or_err<U: ?Sized, F, E>(s: Self, f: F) -> Result<MappedRwLockReadGuard<'a, R, U>, (Self, E)>
where
    F: FnOnce(&T) -> Result<&U, E>,

Attempts to make a new MappedRwLockReadGuard for a component of the locked data. The original guard is returned alongside arbitrary user data if the closure returns Err.

This operation cannot fail as the RwLockReadGuard passed in already locked the data.

This is an associated function that needs to be used as RwLockReadGuard::try_map_or_err(...). A method would interfere with methods of the same name on the contents of the locked data.

fn unlocked<F, U>(s: &mut Self, f: F) -> U
where
    F: FnOnce() -> U,

Temporarily unlocks the RwLock to execute the given function.

This is safe because &mut guarantees that there exist no other references to the data protected by the RwLock.

impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> RwLockReadGuard<'a, R, T>

fn unlock_fair(s: Self)

Unlocks the RwLock using a fair unlock protocol.

By default, RwLock is unfair and allow the current thread to re-lock the RwLock before another has the chance to acquire the lock, even if that thread has been blocked on the RwLock for a long time. This is the default because it allows much higher throughput as it avoids forcing a context switch on every RwLock unlock. This can result in one thread acquiring a RwLock many more times than other threads.

However in some cases it can be beneficial to ensure fairness by forcing the lock to pass on to a waiting thread if there is one. This is done by using this method instead of dropping the RwLockReadGuard normally.

fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U
where
    F: FnOnce() -> U,

Temporarily unlocks the RwLock to execute the given function.

The RwLock is unlocked a fair unlock protocol.

This is safe because &mut guarantees that there exist no other references to the data protected by the RwLock.

fn bump(s: &mut Self)

Temporarily yields the RwLock to a waiting thread if there is one.

This method is functionally equivalent to calling unlock_fair followed by read, however it can be much more efficient in the case where there are no waiting threads.

Trait Implementations

impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for RwLockReadGuard<'a, R, T>

type Target = T;
fn deref(&self) -> &T

impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for RwLockReadGuard<'a, R, T>

fn drop(&mut self)

impl<'a, R: RawRwLock + 'a, T: Debug + ?Sized + 'a> Debug for RwLockReadGuard<'a, R, T>

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

impl<'a, R: RawRwLock + 'a, T: Display + ?Sized + 'a> Display for RwLockReadGuard<'a, R, T>

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

impl<R: RawRwLock + Sync, T: Sync + ?Sized> Sync for RwLockReadGuard<'_, R, T>

Auto Trait Implementations

impl<'a, R, T> !RefUnwindSafe for RwLockReadGuard<'a, R, T>

impl<'a, R, T> !UnwindSafe for RwLockReadGuard<'a, R, T>

impl<'a, R, T> Freeze for RwLockReadGuard<'a, R, T> where &'a RwLock<R, T>: Freeze, PhantomData<(&'a T, <R as RawRwLock>::GuardMarker)>: Freeze, T: ?Sized,

impl<'a, R, T> Send for RwLockReadGuard<'a, R, T> where &'a RwLock<R, T>: Send, PhantomData<(&'a T, <R as RawRwLock>::GuardMarker)>: Send, T: ?Sized,

impl<'a, R, T> Unpin for RwLockReadGuard<'a, R, T> where &'a RwLock<R, T>: Unpin, PhantomData<(&'a T, <R as RawRwLock>::GuardMarker)>: Unpin, T: ?Sized,

impl<'a, R, T> UnsafeUnpin for RwLockReadGuard<'a, R, T> where &'a RwLock<R, T>: UnsafeUnpin, PhantomData<(&'a T, <R as RawRwLock>::GuardMarker)>: UnsafeUnpin, T: ?Sized,

Blanket Implementations

impl<P, T> Receiver for RwLockReadGuard<'a, R, T> where P: Deref<Target = T> + ?Sized, T: ?Sized,

type Target = T;

impl<T> Any for RwLockReadGuard<'a, R, T> where T: 'static + ?Sized,

fn type_id(&self) -> TypeId

impl<T> Borrow<T> for RwLockReadGuard<'a, R, T> where T: ?Sized,

fn borrow(&self) -> &T

impl<T> BorrowMut<T> for RwLockReadGuard<'a, R, T> where T: ?Sized,

fn borrow_mut(&mut self) -> &mut T

impl<T> From<T> for RwLockReadGuard<'a, R, T>

fn from(t: T) -> T

Returns the argument unchanged.

impl<T, U> Into<U> for RwLockReadGuard<'a, R, T> where U: From<T>,

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of [From]<T> for U chooses to do.

impl<T, U> TryFrom<U> for RwLockReadGuard<'a, R, T> where U: Into<T>,

type Error = never;
fn try_from(value: U) -> Result<T, never>

impl<T, U> TryInto<U> for RwLockReadGuard<'a, R, T> where U: TryFrom<T>,

type Error = <U as TryFrom<T>>::Error;
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>