[−][src]Struct tract_hir::internal::tract_downcast_rs::__std::lazy::SyncOnceCell
once_cell
)A synchronization primitive which can be written to only once.
This type is a thread-safe OnceCell
.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; static CELL: SyncOnceCell<String> = SyncOnceCell::new(); assert!(CELL.get().is_none()); std::thread::spawn(|| { let value: &String = CELL.get_or_init(|| { "Hello, World!".to_string() }); assert_eq!(value, "Hello, World!"); }).join().unwrap(); let value: Option<&String> = CELL.get(); assert!(value.is_some()); assert_eq!(value.unwrap().as_str(), "Hello, World!");
Implementations
impl<T> SyncOnceCell<T>
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pub const fn new() -> SyncOnceCell<T>
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once_cell
)Creates a new empty cell.
pub fn get(&self) -> Option<&T>
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once_cell
)Gets the reference to the underlying value.
Returns None
if the cell is empty, or being initialized. This
method never blocks.
pub fn get_mut(&mut self) -> Option<&mut T>
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once_cell
)Gets the mutable reference to the underlying value.
Returns None
if the cell is empty. This method never blocks.
pub fn set(&self, value: T) -> Result<(), T>
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once_cell
)Sets the contents of this cell to value
.
Returns Ok(())
if the cell's value was updated.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; static CELL: SyncOnceCell<i32> = SyncOnceCell::new(); fn main() { assert!(CELL.get().is_none()); std::thread::spawn(|| { assert_eq!(CELL.set(92), Ok(())); }).join().unwrap(); assert_eq!(CELL.set(62), Err(62)); assert_eq!(CELL.get(), Some(&92)); }
pub fn get_or_init<F>(&self, f: F) -> &TⓘNotable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
where
F: FnOnce() -> T,
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Notable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
F: FnOnce() -> T,
once_cell
)Gets the contents of the cell, initializing it with f
if the cell
was empty.
Many threads may call get_or_init
concurrently with different
initializing functions, but it is guaranteed that only one function
will be executed.
Panics
If f
panics, the panic is propagated to the caller, and the cell
remains uninitialized.
It is an error to reentrantly initialize the cell from f
. The
exact outcome is unspecified. Current implementation deadlocks, but
this may be changed to a panic in the future.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; let cell = SyncOnceCell::new(); let value = cell.get_or_init(|| 92); assert_eq!(value, &92); let value = cell.get_or_init(|| unreachable!()); assert_eq!(value, &92);
pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E> where
F: FnOnce() -> Result<T, E>,
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F: FnOnce() -> Result<T, E>,
once_cell
)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.
Panics
If f
panics, the panic is propagated to the caller, and
the cell remains uninitialized.
It is an error to reentrantly initialize the cell from f
.
The exact outcome is unspecified. Current implementation
deadlocks, but this may be changed to a panic in the future.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; let cell = SyncOnceCell::new(); assert_eq!(cell.get_or_try_init(|| Err(())), Err(())); assert!(cell.get().is_none()); let value = cell.get_or_try_init(|| -> Result<i32, ()> { Ok(92) }); assert_eq!(value, Ok(&92)); assert_eq!(cell.get(), Some(&92))
pub fn into_inner(self) -> Option<T>
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once_cell
)Consumes the SyncOnceCell
, returning the wrapped value. Returns
None
if the cell was empty.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; let cell: SyncOnceCell<String> = SyncOnceCell::new(); assert_eq!(cell.into_inner(), None); let cell = SyncOnceCell::new(); cell.set("hello".to_string()).unwrap(); assert_eq!(cell.into_inner(), Some("hello".to_string()));
pub fn take(&mut self) -> Option<T>
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once_cell
)Takes the value out of this SyncOnceCell
, moving it back to an uninitialized state.
Has no effect and returns None
if the SyncOnceCell
hasn't been initialized.
Safety is guaranteed by requiring a mutable reference.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; let mut cell: SyncOnceCell<String> = SyncOnceCell::new(); assert_eq!(cell.take(), None); let mut cell = SyncOnceCell::new(); cell.set("hello".to_string()).unwrap(); assert_eq!(cell.take(), Some("hello".to_string())); assert_eq!(cell.get(), None);
Trait Implementations
impl<T> Clone for SyncOnceCell<T> where
T: Clone,
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T: Clone,
fn clone(&self) -> SyncOnceCell<T>
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fn clone_from(&mut self, source: &Self)
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impl<T> Debug for SyncOnceCell<T> where
T: Debug,
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T: Debug,
impl<T> Default for SyncOnceCell<T>
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fn default() -> SyncOnceCell<T>
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impl<T> Drop for SyncOnceCell<T>
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impl<T> Eq for SyncOnceCell<T> where
T: Eq,
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T: Eq,
impl<T> From<T> for SyncOnceCell<T>
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fn from(value: T) -> SyncOnceCell<T>
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impl<T> PartialEq<SyncOnceCell<T>> for SyncOnceCell<T> where
T: PartialEq<T>,
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T: PartialEq<T>,
fn eq(&self, other: &SyncOnceCell<T>) -> bool
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#[must_use]fn ne(&self, other: &Rhs) -> bool
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impl<T> RefUnwindSafe for SyncOnceCell<T> where
T: UnwindSafe + RefUnwindSafe,
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T: UnwindSafe + RefUnwindSafe,
impl<T> Send for SyncOnceCell<T> where
T: Send,
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T: Send,
impl<T> Sync for SyncOnceCell<T> where
T: Send + Sync,
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T: Send + Sync,
impl<T> UnwindSafe for SyncOnceCell<T> where
T: UnwindSafe,
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T: UnwindSafe,
Auto Trait Implementations
impl<T> Unpin for SyncOnceCell<T> where
T: Unpin,
T: Unpin,
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow(&self) -> &TⓘNotable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
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Notable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
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Notable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
impl<T> Downcast for T where
T: Any,
T: Any,
fn into_any(self: Box<T>) -> Box<dyn Any + 'static>ⓘNotable traits for Box<R>
impl<R> Read for Box<R> where
R: Read + ?Sized, impl<W> Write for Box<W> where
W: Write + ?Sized, impl<F> Future for Box<F> where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
Notable traits for Box<R>
impl<R> Read for Box<R> where
R: Read + ?Sized, impl<W> Write for Box<W> where
W: Write + ?Sized, impl<F> Future for Box<F> where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
fn as_any(&self) -> &(dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
impl<T> DowncastSync for T where
T: Send + Sync + Any,
T: Send + Sync + Any,
impl<T> DynClone for T where
T: Clone,
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T: Clone,
impl<T> From<!> for T
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
type Owned = T
The resulting type after obtaining ownership.
fn to_owned(&self) -> T
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fn clone_into(&self, target: &mut T)
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
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>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,