# [−][src]Struct lock_api::MappedMutexGuard

    #[must_use]
    pub struct MappedMutexGuard<'a, R: RawMutex + 'a, T: ?Sized + 'a> { /* fields omitted */ }

An RAII mutex guard returned by `MutexGuard::map`, which can point to a subfield of the protected data.

The main difference between `MappedMutexGuard` and `MutexGuard` 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.

## Methods

### `impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> MappedMutexGuard<'a, R, T>`[src]

#### `pub fn map<U: ?Sized, F>(s: Self, f: F) -> MappedMutexGuard<'a, R, U> where
F: FnOnce(&mut T) -> &mut U,` [src]

Makes a new `MappedMutexGuard` for a component of the locked data.

This operation cannot fail as the `MappedMutexGuard` passed in already locked the mutex.

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

#### `pub fn try_map<U: ?Sized, F>(
s: Self,
f: F
) -> Result<MappedMutexGuard<'a, R, U>, Self> where
F: FnOnce(&mut T) -> Option<&mut U>,` [src]

Attempts to make a new `MappedMutexGuard` for a component of the locked data. The original guard is return if the closure returns `None`.

This operation cannot fail as the `MappedMutexGuard` passed in already locked the mutex.

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

### `impl<'a, R: RawMutexFair + 'a, T: ?Sized + 'a> MappedMutexGuard<'a, R, T>`[src]

#### `pub fn unlock_fair(s: Self)`[src]

Unlocks the mutex using a fair unlock protocol.

By default, mutexes are unfair and allow the current thread to re-lock the mutex before another has the chance to acquire the lock, even if that thread has been blocked on the mutex for a long time. This is the default because it allows much higher throughput as it avoids forcing a context switch on every mutex unlock. This can result in one thread acquiring a mutex 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 `MutexGuard` normally.

## Trait Implementations

### `impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> DerefMut for MappedMutexGuard<'a, R, T>`[src]

#### `fn deref_mut(&mut self) -> &mut T`[src]

Mutably dereferences the value.

### `impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Deref for MappedMutexGuard<'a, R, T>`[src]

#### `type Target = T`

The resulting type after dereferencing.

#### `fn deref(&self) -> &T`[src]

Dereferences the value.

### `impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Drop for MappedMutexGuard<'a, R, T>`[src]

#### `fn drop(&mut self)`[src]

Executes the destructor for this type. Read more

### `impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Send for MappedMutexGuard<'a, R, T> where
R::GuardMarker: Send,` [src]

### `impl<'a, R: RawMutex + Sync + 'a, T: ?Sized + Sync + 'a> Sync for MappedMutexGuard<'a, R, T>`[src]

### `impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> StableDeref for MappedMutexGuard<'a, R, T>`[src]

## Auto Trait Implementations

### `impl<'a, R, T: ?Sized> Unpin for MappedMutexGuard<'a, R, T>`

### `impl<'a, R, T> !UnwindSafe for MappedMutexGuard<'a, R, T>`

### `impl<'a, R, T: ?Sized> RefUnwindSafe for MappedMutexGuard<'a, R, T> where
R: RefUnwindSafe,
T: RefUnwindSafe,`

## Blanket Implementations

### `impl<T> From<T> for T`[src]

#### `fn from(t: T) -> T`[src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `fn into(self) -> U`[src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`[src]

Performs the conversion.

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `fn borrow_mut(&mut self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Erased for T`[src]

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)