Struct OnceBox

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pub struct OnceBox<T> { /* private fields */ }
Expand description

A thread-safe cell which can be written to only once.

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impl<T> OnceBox<T>

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pub const fn new() -> Self

Creates a new empty cell.

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pub fn with_value(value: Box<T>) -> Self

Creates a new cell with the given value.

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pub fn get(&self) -> Option<&T>

Gets a reference to the underlying value.

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pub fn set(&self, value: Box<T>) -> Result<(), Box<T>>

Sets the contents of this cell to value.

Returns Ok(()) if the cell was empty and Err(value) if it was full.

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pub fn get_or_init<F>(&self, f: F) -> &T
where F: FnOnce() -> Box<T>,

Gets the contents of the cell, initializing it with f if the cell was empty.

If several threads concurrently run get_or_init, more than one f can be called. However, all threads will return the same value, produced by some f.

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pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E>
where F: FnOnce() -> Result<Box<T>, E>,

Gets the contents of the cell, initializing it with f if the cell was empty. If the cell was empty and f failed, an error is returned.

If several threads concurrently run get_or_init, more than one f can be called. However, all threads will return the same value, produced by some f.

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impl<T: Clone> Clone for OnceBox<T>

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fn clone(&self) -> Self

Returns a duplicate of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<T> Debug for OnceBox<T>

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

Formats the value using the given formatter. Read more
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impl<T> Default for OnceBox<T>

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fn default() -> Self

Returns the “default value” for a type. Read more
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impl<T> Drop for OnceBox<T>

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fn drop(&mut self)

Executes the destructor for this type. Read more
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impl<T: Sync + Send> Sync for OnceBox<T>

Auto Trait Implementations§

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impl<T> !Freeze for OnceBox<T>

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impl<T> RefUnwindSafe for OnceBox<T>
where T: RefUnwindSafe,

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impl<T> Send for OnceBox<T>
where T: Send,

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impl<T> Unpin for OnceBox<T>

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impl<T> UnwindSafe for OnceBox<T>

Blanket Implementations§

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

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dest. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

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

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 8 bytes