integrate Lazy into std layout
This commit refactors the initial implementation to fit into std and makes some other changes: - use MaybeUninit internally in SyncOnceCell - correctly impl Drop for lazy::Once - port Lazy::take from once_cell from: https://github.com/matklad/once_cell/pull/100 Co-Authored-By: Paul Dicker <pitdicker@users.noreply.github.com>
This commit is contained in:
Ashley Mannix
parent
cac1768b03
commit
237a97760a
7 changed files with 1004 additions and 548 deletions
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@ -1372,8 +1372,8 @@ checksum = "7e81a7c05f79578dbc15793d8b619db9ba32b4577003ef3af1a91c416798c58d"
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name = "installer"
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version = "0.0.0"
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dependencies = [
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"anyhow",
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"clap",
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"failure",
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"flate2",
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"lazy_static",
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"num_cpus",
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379
src/libcore/lazy.rs
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379
src/libcore/lazy.rs
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@ -0,0 +1,379 @@
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//! Lazy values and one-time initialization of static data.
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use crate::cell::{Cell, UnsafeCell};
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use crate::fmt;
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use crate::mem;
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use crate::ops::Deref;
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/// A cell which can be written to only once.
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///
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/// Unlike `RefCell`, a `OnceCell` only provides shared `&T` references to its value.
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/// Unlike `Cell`, a `OnceCell` doesn't require copying or replacing the value to access it.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::lazy::OnceCell;
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///
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/// let cell = OnceCell::new();
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/// assert!(cell.get().is_none());
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///
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/// let value: &String = cell.get_or_init(|| {
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/// "Hello, World!".to_string()
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/// });
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/// assert_eq!(value, "Hello, World!");
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/// assert!(cell.get().is_some());
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub struct OnceCell<T> {
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// Invariant: written to at most once.
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inner: UnsafeCell<Option<T>>,
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}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T> Default for OnceCell<T> {
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fn default() -> Self {
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Self::new()
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}
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}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T: fmt::Debug> fmt::Debug for OnceCell<T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self.get() {
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Some(v) => f.debug_tuple("OnceCell").field(v).finish(),
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None => f.write_str("OnceCell(Uninit)"),
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}
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}
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}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T: Clone> Clone for OnceCell<T> {
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fn clone(&self) -> OnceCell<T> {
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let res = OnceCell::new();
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if let Some(value) = self.get() {
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match res.set(value.clone()) {
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Ok(()) => (),
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Err(_) => unreachable!(),
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}
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}
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res
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}
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}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T: PartialEq> PartialEq for OnceCell<T> {
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fn eq(&self, other: &Self) -> bool {
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self.get() == other.get()
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}
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}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T: Eq> Eq for OnceCell<T> {}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T> From<T> for OnceCell<T> {
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fn from(value: T) -> Self {
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OnceCell { inner: UnsafeCell::new(Some(value)) }
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}
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}
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impl<T> OnceCell<T> {
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/// Creates a new empty cell.
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#[unstable(feature = "once_cell", issue = "68198")]
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pub const fn new() -> OnceCell<T> {
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OnceCell { inner: UnsafeCell::new(None) }
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}
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/// Gets the reference to the underlying value.
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///
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/// Returns `None` if the cell is empty.
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#[unstable(feature = "once_cell", issue = "68198")]
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pub fn get(&self) -> Option<&T> {
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// Safety: Safe due to `inner`'s invariant
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unsafe { &*self.inner.get() }.as_ref()
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}
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/// Gets the mutable reference to the underlying value.
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///
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/// Returns `None` if the cell is empty.
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#[unstable(feature = "once_cell", issue = "68198")]
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pub fn get_mut(&mut self) -> Option<&mut T> {
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// Safety: Safe because we have unique access
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unsafe { &mut *self.inner.get() }.as_mut()
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}
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/// Sets the contents of the cell to `value`.
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///
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/// # Errors
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///
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/// This method returns `Ok(())` if the cell was empty and `Err(value)` if
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/// it was full.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::lazy::OnceCell;
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///
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/// let cell = OnceCell::new();
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/// assert!(cell.get().is_none());
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///
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/// assert_eq!(cell.set(92), Ok(()));
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/// assert_eq!(cell.set(62), Err(62));
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///
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/// assert!(cell.get().is_some());
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub fn set(&self, value: T) -> Result<(), T> {
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// Safety: Safe because we cannot have overlapping mutable borrows
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let slot = unsafe { &*self.inner.get() };
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if slot.is_some() {
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return Err(value);
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}
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// Safety: This is the only place where we set the slot, no races
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// due to reentrancy/concurrency are possible, and we've
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// checked that slot is currently `None`, so this write
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// maintains the `inner`'s invariant.
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let slot = unsafe { &mut *self.inner.get() };
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*slot = Some(value);
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Ok(())
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}
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/// Gets the contents of the cell, initializing it with `f`
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/// if the cell was empty.
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///
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/// # Panics
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///
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/// If `f` panics, the panic is propagated to the caller, and the cell
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/// remains uninitialized.
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///
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/// It is an error to reentrantly initialize the cell from `f`. Doing
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/// so results in a panic.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::lazy::OnceCell;
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///
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/// let cell = OnceCell::new();
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/// let value = cell.get_or_init(|| 92);
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/// assert_eq!(value, &92);
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/// let value = cell.get_or_init(|| unreachable!());
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/// assert_eq!(value, &92);
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub fn get_or_init<F>(&self, f: F) -> &T
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where
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F: FnOnce() -> T,
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{
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match self.get_or_try_init(|| Ok::<T, !>(f())) {
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Ok(val) => val,
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}
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}
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/// Gets the contents of the cell, initializing it with `f` if
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/// the cell was empty. If the cell was empty and `f` failed, an
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/// error is returned.
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///
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/// # Panics
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///
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/// If `f` panics, the panic is propagated to the caller, and the cell
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/// remains uninitialized.
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///
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/// It is an error to reentrantly initialize the cell from `f`. Doing
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/// so results in a panic.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::lazy::OnceCell;
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///
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/// let cell = OnceCell::new();
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/// assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
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/// assert!(cell.get().is_none());
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/// let value = cell.get_or_try_init(|| -> Result<i32, ()> {
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/// Ok(92)
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/// });
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/// assert_eq!(value, Ok(&92));
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/// assert_eq!(cell.get(), Some(&92))
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E>
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where
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F: FnOnce() -> Result<T, E>,
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{
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if let Some(val) = self.get() {
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return Ok(val);
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}
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let val = f()?;
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// Note that *some* forms of reentrant initialization might lead to
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// UB (see `reentrant_init` test). I believe that just removing this
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// `assert`, while keeping `set/get` would be sound, but it seems
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// better to panic, rather than to silently use an old value.
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assert!(self.set(val).is_ok(), "reentrant init");
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Ok(self.get().unwrap())
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}
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/// Consumes the cell, returning the wrapped value.
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///
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/// Returns `None` if the cell was empty.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::lazy::OnceCell;
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///
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/// let cell: OnceCell<String> = OnceCell::new();
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/// assert_eq!(cell.into_inner(), None);
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///
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/// let cell = OnceCell::new();
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/// cell.set("hello".to_string()).unwrap();
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/// assert_eq!(cell.into_inner(), Some("hello".to_string()));
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub fn into_inner(self) -> Option<T> {
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// Because `into_inner` takes `self` by value, the compiler statically verifies
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// that it is not currently borrowed. So it is safe to move out `Option<T>`.
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self.inner.into_inner()
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}
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/// Takes the value out of this `OnceCell`, moving it back to an uninitialized state.
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///
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/// Has no effect and returns `None` if the `OnceCell` hasn't been initialized.
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///
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/// Safety is guaranteed by requiring a mutable reference.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::lazy::OnceCell;
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///
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/// let mut cell: OnceCell<String> = OnceCell::new();
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/// assert_eq!(cell.take(), None);
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///
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/// let mut cell = OnceCell::new();
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/// cell.set("hello".to_string()).unwrap();
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/// assert_eq!(cell.take(), Some("hello".to_string()));
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/// assert_eq!(cell.get(), None);
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub fn take(&mut self) -> Option<T> {
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mem::take(self).into_inner()
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}
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}
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/// A value which is initialized on the first access.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::lazy::Lazy;
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///
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/// let lazy: Lazy<i32> = Lazy::new(|| {
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/// println!("initializing");
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/// 92
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/// });
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/// println!("ready");
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/// println!("{}", *lazy);
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/// println!("{}", *lazy);
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///
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/// // Prints:
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/// // ready
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/// // initializing
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/// // 92
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/// // 92
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub struct Lazy<T, F = fn() -> T> {
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cell: OnceCell<T>,
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init: Cell<Option<F>>,
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}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T: fmt::Debug, F> fmt::Debug for Lazy<T, F> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("Lazy").field("cell", &self.cell).field("init", &"..").finish()
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}
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}
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impl<T, F> Lazy<T, F> {
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/// Creates a new lazy value with the given initializing function.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// # fn main() {
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/// use std::lazy::Lazy;
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///
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/// let hello = "Hello, World!".to_string();
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///
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/// let lazy = Lazy::new(|| hello.to_uppercase());
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///
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/// assert_eq!(&*lazy, "HELLO, WORLD!");
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/// # }
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub const fn new(init: F) -> Lazy<T, F> {
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Lazy { cell: OnceCell::new(), init: Cell::new(Some(init)) }
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}
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}
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impl<T, F: FnOnce() -> T> Lazy<T, F> {
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/// Forces the evaluation of this lazy value and returns a reference to
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/// the result.
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///
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/// This is equivalent to the `Deref` impl, but is explicit.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::lazy::Lazy;
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///
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/// let lazy = Lazy::new(|| 92);
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///
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/// assert_eq!(Lazy::force(&lazy), &92);
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/// assert_eq!(&*lazy, &92);
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/// ```
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#[unstable(feature = "once_cell", issue = "68198")]
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pub fn force(this: &Lazy<T, F>) -> &T {
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this.cell.get_or_init(|| match this.init.take() {
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Some(f) => f(),
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None => panic!("`Lazy` instance has previously been poisoned"),
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})
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}
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}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
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type Target = T;
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fn deref(&self) -> &T {
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Lazy::force(self)
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}
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}
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#[unstable(feature = "once_cell", issue = "68198")]
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impl<T: Default> Default for Lazy<T> {
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/// Creates a new lazy value using `Default` as the initializing function.
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fn default() -> Lazy<T> {
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Lazy::new(T::default)
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}
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}
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@ -239,6 +239,8 @@ pub mod char;
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pub mod ffi;
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#[cfg(not(test))] // See #65860
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pub mod iter;
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#[unstable(feature = "once_cell", issue = "68198")]
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pub mod lazy;
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pub mod option;
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pub mod panic;
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pub mod panicking;
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124
src/libcore/tests/lazy.rs
Normal file
124
src/libcore/tests/lazy.rs
Normal file
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@ -0,0 +1,124 @@
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use core::{
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cell::Cell,
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lazy::{Lazy, OnceCell},
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sync::atomic::{AtomicUsize, Ordering::SeqCst},
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};
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#[test]
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fn once_cell() {
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let c = OnceCell::new();
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assert!(c.get().is_none());
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c.get_or_init(|| 92);
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assert_eq!(c.get(), Some(&92));
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c.get_or_init(|| panic!("Kabom!"));
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assert_eq!(c.get(), Some(&92));
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}
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#[test]
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fn once_cell_get_mut() {
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let mut c = OnceCell::new();
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assert!(c.get_mut().is_none());
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c.set(90).unwrap();
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*c.get_mut().unwrap() += 2;
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assert_eq!(c.get_mut(), Some(&mut 92));
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}
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#[test]
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fn once_cell_drop() {
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static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
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struct Dropper;
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impl Drop for Dropper {
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fn drop(&mut self) {
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DROP_CNT.fetch_add(1, SeqCst);
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}
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}
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let x = OnceCell::new();
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x.get_or_init(|| Dropper);
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assert_eq!(DROP_CNT.load(SeqCst), 0);
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drop(x);
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assert_eq!(DROP_CNT.load(SeqCst), 1);
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}
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#[test]
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fn unsync_once_cell_drop_empty() {
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let x = OnceCell::<&'static str>::new();
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drop(x);
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}
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#[test]
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fn clone() {
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let s = OnceCell::new();
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let c = s.clone();
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assert!(c.get().is_none());
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s.set("hello").unwrap();
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let c = s.clone();
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assert_eq!(c.get().map(|c| *c), Some("hello"));
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}
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#[test]
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fn from_impl() {
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assert_eq!(OnceCell::from("value").get(), Some(&"value"));
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assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
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}
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#[test]
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fn partialeq_impl() {
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assert!(OnceCell::from("value") == OnceCell::from("value"));
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assert!(OnceCell::from("foo") != OnceCell::from("bar"));
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assert!(OnceCell::<&'static str>::new() == OnceCell::new());
|
||||
assert!(OnceCell::<&'static str>::new() != OnceCell::from("value"));
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn into_inner() {
|
||||
let cell: OnceCell<&'static str> = OnceCell::new();
|
||||
assert_eq!(cell.into_inner(), None);
|
||||
let cell = OnceCell::new();
|
||||
cell.set("hello").unwrap();
|
||||
assert_eq!(cell.into_inner(), Some("hello"));
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn lazy_new() {
|
||||
let called = Cell::new(0);
|
||||
let x = Lazy::new(|| {
|
||||
called.set(called.get() + 1);
|
||||
92
|
||||
});
|
||||
|
||||
assert_eq!(called.get(), 0);
|
||||
|
||||
let y = *x - 30;
|
||||
assert_eq!(y, 62);
|
||||
assert_eq!(called.get(), 1);
|
||||
|
||||
let y = *x - 30;
|
||||
assert_eq!(y, 62);
|
||||
assert_eq!(called.get(), 1);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn aliasing_in_get() {
|
||||
let x = OnceCell::new();
|
||||
x.set(42).unwrap();
|
||||
let at_x = x.get().unwrap(); // --- (shared) borrow of inner `Option<T>` --+
|
||||
let _ = x.set(27); // <-- temporary (unique) borrow of inner `Option<T>` |
|
||||
println!("{}", at_x); // <------- up until here ---------------------------+
|
||||
}
|
||||
|
||||
#[test]
|
||||
#[should_panic(expected = "reentrant init")]
|
||||
fn reentrant_init() {
|
||||
let x: OnceCell<Box<i32>> = OnceCell::new();
|
||||
let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
|
||||
x.get_or_init(|| {
|
||||
let r = x.get_or_init(|| Box::new(92));
|
||||
dangling_ref.set(Some(r));
|
||||
Box::new(62)
|
||||
});
|
||||
eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
|
||||
}
|
||||
|
|
@ -43,6 +43,7 @@
|
|||
#![feature(option_unwrap_none)]
|
||||
#![feature(peekable_next_if)]
|
||||
#![feature(partition_point)]
|
||||
#![feature(once_cell)]
|
||||
#![feature(unsafe_block_in_unsafe_fn)]
|
||||
#![deny(unsafe_op_in_unsafe_fn)]
|
||||
|
||||
|
|
@ -62,6 +63,7 @@ mod fmt;
|
|||
mod hash;
|
||||
mod intrinsics;
|
||||
mod iter;
|
||||
mod lazy;
|
||||
mod manually_drop;
|
||||
mod mem;
|
||||
mod nonzero;
|
||||
|
|
|
|||
1030
src/libstd/lazy.rs
1030
src/libstd/lazy.rs
File diff suppressed because it is too large
Load diff
|
|
@ -285,6 +285,7 @@
|
|||
#![feature(linkage)]
|
||||
#![feature(llvm_asm)]
|
||||
#![feature(log_syntax)]
|
||||
#![feature(maybe_uninit_extra)]
|
||||
#![feature(maybe_uninit_ref)]
|
||||
#![feature(maybe_uninit_slice)]
|
||||
#![feature(min_specialization)]
|
||||
|
|
@ -292,6 +293,7 @@
|
|||
#![feature(negative_impls)]
|
||||
#![feature(never_type)]
|
||||
#![feature(nll)]
|
||||
#![feature(once_cell)]
|
||||
#![feature(optin_builtin_traits)]
|
||||
#![feature(or_patterns)]
|
||||
#![feature(panic_info_message)]
|
||||
|
|
@ -476,10 +478,7 @@ pub mod process;
|
|||
pub mod sync;
|
||||
pub mod time;
|
||||
|
||||
#[unstable(
|
||||
feature = "std_lazy",
|
||||
issue = "99",
|
||||
)]
|
||||
#[unstable(feature = "once_cell", issue = "68198")]
|
||||
pub mod lazy;
|
||||
|
||||
#[stable(feature = "futures_api", since = "1.36.0")]
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue