diff options
Diffstat (limited to 'library/std/src/sync/once_lock.rs')
| -rw-r--r-- | library/std/src/sync/once_lock.rs | 72 |
1 files changed, 37 insertions, 35 deletions
diff --git a/library/std/src/sync/once_lock.rs b/library/std/src/sync/once_lock.rs index 49f2dafd8fd..21e6b65a744 100644 --- a/library/std/src/sync/once_lock.rs +++ b/library/std/src/sync/once_lock.rs @@ -13,6 +13,9 @@ use crate::sync::Once; /// Where OnceLock shines is when LazyLock is too simple to support a given case, as LazyLock /// doesn't allow additional inputs to its function after you call [`LazyLock::new(|| ...)`]. /// +/// A `OnceLock` can be thought of as a safe abstraction over uninitialized data that becomes +/// initialized once written. +/// /// [`OnceCell`]: crate::cell::OnceCell /// [`LazyLock<T, F>`]: crate::sync::LazyLock /// [`LazyLock::new(|| ...)`]: crate::sync::LazyLock::new @@ -126,7 +129,7 @@ pub struct OnceLock<T> { } impl<T> OnceLock<T> { - /// Creates a new empty cell. + /// Creates a new uninitialized cell. #[inline] #[must_use] #[stable(feature = "once_cell", since = "1.70.0")] @@ -141,8 +144,8 @@ impl<T> OnceLock<T> { /// Gets the reference to the underlying value. /// - /// Returns `None` if the cell is empty, or being initialized. This - /// method never blocks. + /// Returns `None` if the cell is uninitialized, or being initialized. + /// This method never blocks. #[inline] #[stable(feature = "once_cell", since = "1.70.0")] pub fn get(&self) -> Option<&T> { @@ -156,7 +159,8 @@ impl<T> OnceLock<T> { /// Gets the mutable reference to the underlying value. /// - /// Returns `None` if the cell is empty. This method never blocks. + /// Returns `None` if the cell is uninitialized, or being initialized. + /// This method never blocks. #[inline] #[stable(feature = "once_cell", since = "1.70.0")] pub fn get_mut(&mut self) -> Option<&mut T> { @@ -174,8 +178,6 @@ impl<T> OnceLock<T> { /// /// Waiting for a computation on another thread to finish: /// ```rust - /// #![feature(once_wait)] - /// /// use std::thread; /// use std::sync::OnceLock; /// @@ -189,19 +191,20 @@ impl<T> OnceLock<T> { /// }) /// ``` #[inline] - #[unstable(feature = "once_wait", issue = "127527")] + #[stable(feature = "once_wait", since = "CURRENT_RUSTC_VERSION")] pub fn wait(&self) -> &T { self.once.wait_force(); unsafe { self.get_unchecked() } } - /// Sets the contents of this cell to `value`. + /// Initializes the contents of the cell to `value`. /// /// May block if another thread is currently attempting to initialize the cell. The cell is - /// guaranteed to contain a value when set returns, though not necessarily the one provided. + /// guaranteed to contain a value when `set` returns, though not necessarily the one provided. /// - /// Returns `Ok(())` if the cell's value was set by this call. + /// Returns `Ok(())` if the cell was uninitialized and + /// `Err(value)` if the cell was already initialized. /// /// # Examples /// @@ -230,13 +233,15 @@ impl<T> OnceLock<T> { } } - /// Sets the contents of this cell to `value` if the cell was empty, then - /// returns a reference to it. + /// Initializes the contents of the cell to `value` if the cell was uninitialized, + /// then returns a reference to it. /// /// May block if another thread is currently attempting to initialize the cell. The cell is - /// guaranteed to contain a value when set returns, though not necessarily the one provided. + /// guaranteed to contain a value when `try_insert` returns, though not necessarily the + /// one provided. /// - /// Returns `Ok(&value)` if the cell was empty and `Err(¤t_value, value)` if it was full. + /// Returns `Ok(&value)` if the cell was uninitialized and + /// `Err((¤t_value, value))` if it was already initialized. /// /// # Examples /// @@ -269,8 +274,8 @@ impl<T> OnceLock<T> { } } - /// Gets the contents of the cell, initializing it with `f` if the cell - /// was empty. + /// Gets the contents of the cell, initializing it to `f()` if the cell + /// was uninitialized. /// /// Many threads may call `get_or_init` concurrently with different /// initializing functions, but it is guaranteed that only one function @@ -278,7 +283,7 @@ impl<T> OnceLock<T> { /// /// # Panics /// - /// If `f` panics, the panic is propagated to the caller, and the cell + /// 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 @@ -308,13 +313,13 @@ impl<T> OnceLock<T> { } /// Gets the mutable reference of the contents of the cell, initializing - /// it with `f` if the cell was empty. + /// it to `f()` if the cell was uninitialized. /// /// This method never blocks. /// /// # Panics /// - /// If `f` panics, the panic is propagated to the caller, and the cell + /// If `f()` panics, the panic is propagated to the caller, and the cell /// remains uninitialized. /// /// # Examples @@ -345,13 +350,13 @@ impl<T> OnceLock<T> { } } - /// 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. + /// Gets the contents of the cell, initializing it to `f()` if + /// the cell was uninitialized. If the cell was uninitialized + /// and `f()` failed, an error is returned. /// /// # Panics /// - /// If `f` panics, the panic is propagated to the caller, and + /// 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`. @@ -397,14 +402,14 @@ impl<T> OnceLock<T> { } /// Gets the mutable reference of 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. + /// it to `f()` if the cell was uninitialized. If the cell was uninitialized + /// and `f()` failed, an error is returned. /// /// This method never blocks. /// /// # Panics /// - /// If `f` panics, the panic is propagated to the caller, and + /// If `f()` panics, the panic is propagated to the caller, and /// the cell remains uninitialized. /// /// # Examples @@ -416,7 +421,7 @@ impl<T> OnceLock<T> { /// /// let mut cell: OnceLock<u32> = OnceLock::new(); /// - /// // Failed initializers do not change the value + /// // Failed attempts to initialize the cell do not change its contents /// assert!(cell.get_mut_or_try_init(|| "not a number!".parse()).is_err()); /// assert!(cell.get().is_none()); /// @@ -440,7 +445,7 @@ impl<T> OnceLock<T> { } /// Consumes the `OnceLock`, returning the wrapped value. Returns - /// `None` if the cell was empty. + /// `None` if the cell was uninitialized. /// /// # Examples /// @@ -462,7 +467,7 @@ impl<T> OnceLock<T> { /// Takes the value out of this `OnceLock`, moving it back to an uninitialized state. /// - /// Has no effect and returns `None` if the `OnceLock` hasn't been initialized. + /// Has no effect and returns `None` if the `OnceLock` was uninitialized. /// /// Safety is guaranteed by requiring a mutable reference. /// @@ -528,7 +533,7 @@ impl<T> OnceLock<T> { /// # Safety /// - /// The value must be initialized + /// The cell must be initialized #[inline] unsafe fn get_unchecked(&self) -> &T { debug_assert!(self.is_initialized()); @@ -537,7 +542,7 @@ impl<T> OnceLock<T> { /// # Safety /// - /// The value must be initialized + /// The cell must be initialized #[inline] unsafe fn get_unchecked_mut(&mut self) -> &mut T { debug_assert!(self.is_initialized()); @@ -562,7 +567,7 @@ impl<T: UnwindSafe> UnwindSafe for OnceLock<T> {} #[stable(feature = "once_cell", since = "1.70.0")] impl<T> Default for OnceLock<T> { - /// Creates a new empty cell. + /// Creates a new uninitialized cell. /// /// # Example /// @@ -676,6 +681,3 @@ unsafe impl<#[may_dangle] T> Drop for OnceLock<T> { } } } - -#[cfg(test)] -mod tests; |