Struct MappedRwLockReadGuard

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

An RAII read lock guard returned by RwLockReadGuard::map, which can point to a subfield of the protected data.

The main difference between MappedRwLockReadGuard and RwLockReadGuard is that the former doesn't support temporarily unlocking and re-locking, since that could introduce soundness issues if the locked object is modified by another thread.

Implementations

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

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 MappedRwLockReadGuard passed in already locked the data.

This is an associated function that needs to be used as MappedRwLockReadGuard::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. The original guard is return if the closure returns None.

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

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

fn try_map_or_else<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 MappedRwLockReadGuard passed in already locked the data.

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

impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> MappedRwLockReadGuard<'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 MappedRwLockReadGuard normally.

Trait Implementations

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

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

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

fn drop(&mut self)

impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Send for MappedRwLockReadGuard<'a, R, T> where R::GuardMarker: Send,

impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Sync for MappedRwLockReadGuard<'a, R, T>

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

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

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

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

Auto Trait Implementations

impl<'a, R, T> Freeze for MappedRwLockReadGuard<'a, R, T> where &'a R: Freeze, *const T: Freeze, PhantomData<&'a T>: Freeze, T: ?Sized,

impl<'a, R, T> RefUnwindSafe for MappedRwLockReadGuard<'a, R, T> where &'a R: RefUnwindSafe, *const T: RefUnwindSafe, PhantomData<&'a T>: RefUnwindSafe, T: ?Sized,

impl<'a, R, T> Unpin for MappedRwLockReadGuard<'a, R, T> where &'a R: Unpin, *const T: Unpin, PhantomData<&'a T>: Unpin, T: ?Sized,

impl<'a, R, T> UnsafeUnpin for MappedRwLockReadGuard<'a, R, T> where &'a R: UnsafeUnpin, *const T: UnsafeUnpin, PhantomData<&'a T>: UnsafeUnpin, T: ?Sized,

impl<'a, R, T> UnwindSafe for MappedRwLockReadGuard<'a, R, T> where &'a R: UnwindSafe, *const T: UnwindSafe, PhantomData<&'a T>: UnwindSafe, T: ?Sized,

Blanket Implementations

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

type Target = T;

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

fn type_id(&self) -> TypeId

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

fn borrow(&self) -> &T

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

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

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

fn from(t: T) -> T

Returns the argument unchanged.

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

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

impl<T, U> TryInto<U> for MappedRwLockReadGuard<'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>