aboutsummaryrefslogtreecommitdiff
path: root/vendor/once_cell/src/race.rs
diff options
context:
space:
mode:
Diffstat (limited to 'vendor/once_cell/src/race.rs')
-rw-r--r--vendor/once_cell/src/race.rs419
1 files changed, 0 insertions, 419 deletions
diff --git a/vendor/once_cell/src/race.rs b/vendor/once_cell/src/race.rs
deleted file mode 100644
index da8a2fc..0000000
--- a/vendor/once_cell/src/race.rs
+++ /dev/null
@@ -1,419 +0,0 @@
-//! Thread-safe, non-blocking, "first one wins" flavor of `OnceCell`.
-//!
-//! If two threads race to initialize a type from the `race` module, they
-//! don't block, execute initialization function together, but only one of
-//! them stores the result.
-//!
-//! This module does not require `std` feature.
-//!
-//! # Atomic orderings
-//!
-//! All types in this module use `Acquire` and `Release`
-//! [atomic orderings](Ordering) for all their operations. While this is not
-//! strictly necessary for types other than `OnceBox`, it is useful for users as
-//! it allows them to be certain that after `get` or `get_or_init` returns on
-//! one thread, any side-effects caused by the setter thread prior to them
-//! calling `set` or `get_or_init` will be made visible to that thread; without
-//! it, it's possible for it to appear as if they haven't happened yet from the
-//! getter thread's perspective. This is an acceptable tradeoff to make since
-//! `Acquire` and `Release` have very little performance overhead on most
-//! architectures versus `Relaxed`.
-
-#[cfg(feature = "critical-section")]
-use portable_atomic as atomic;
-#[cfg(not(feature = "critical-section"))]
-use core::sync::atomic;
-
-use atomic::{AtomicPtr, AtomicUsize, Ordering};
-use core::cell::UnsafeCell;
-use core::marker::PhantomData;
-use core::num::NonZeroUsize;
-use core::ptr;
-
-/// A thread-safe cell which can be written to only once.
-#[derive(Default, Debug)]
-pub struct OnceNonZeroUsize {
- inner: AtomicUsize,
-}
-
-impl OnceNonZeroUsize {
- /// Creates a new empty cell.
- #[inline]
- pub const fn new() -> OnceNonZeroUsize {
- OnceNonZeroUsize { inner: AtomicUsize::new(0) }
- }
-
- /// Gets the underlying value.
- #[inline]
- pub fn get(&self) -> Option<NonZeroUsize> {
- let val = self.inner.load(Ordering::Acquire);
- NonZeroUsize::new(val)
- }
-
- /// Sets the contents of this cell to `value`.
- ///
- /// Returns `Ok(())` if the cell was empty and `Err(())` if it was
- /// full.
- #[inline]
- pub fn set(&self, value: NonZeroUsize) -> Result<(), ()> {
- let exchange =
- self.inner.compare_exchange(0, value.get(), Ordering::AcqRel, Ordering::Acquire);
- match exchange {
- Ok(_) => Ok(()),
- Err(_) => Err(()),
- }
- }
-
- /// 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`.
- pub fn get_or_init<F>(&self, f: F) -> NonZeroUsize
- where
- F: FnOnce() -> NonZeroUsize,
- {
- enum Void {}
- match self.get_or_try_init(|| Ok::<NonZeroUsize, Void>(f())) {
- Ok(val) => val,
- Err(void) => match void {},
- }
- }
-
- /// 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`.
- pub fn get_or_try_init<F, E>(&self, f: F) -> Result<NonZeroUsize, E>
- where
- F: FnOnce() -> Result<NonZeroUsize, E>,
- {
- let val = self.inner.load(Ordering::Acquire);
- let res = match NonZeroUsize::new(val) {
- Some(it) => it,
- None => {
- let mut val = f()?.get();
- let exchange =
- self.inner.compare_exchange(0, val, Ordering::AcqRel, Ordering::Acquire);
- if let Err(old) = exchange {
- val = old;
- }
- unsafe { NonZeroUsize::new_unchecked(val) }
- }
- };
- Ok(res)
- }
-}
-
-/// A thread-safe cell which can be written to only once.
-#[derive(Default, Debug)]
-pub struct OnceBool {
- inner: OnceNonZeroUsize,
-}
-
-impl OnceBool {
- /// Creates a new empty cell.
- #[inline]
- pub const fn new() -> OnceBool {
- OnceBool { inner: OnceNonZeroUsize::new() }
- }
-
- /// Gets the underlying value.
- #[inline]
- pub fn get(&self) -> Option<bool> {
- self.inner.get().map(OnceBool::from_usize)
- }
-
- /// Sets the contents of this cell to `value`.
- ///
- /// Returns `Ok(())` if the cell was empty and `Err(())` if it was
- /// full.
- #[inline]
- pub fn set(&self, value: bool) -> Result<(), ()> {
- self.inner.set(OnceBool::to_usize(value))
- }
-
- /// 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`.
- pub fn get_or_init<F>(&self, f: F) -> bool
- where
- F: FnOnce() -> bool,
- {
- OnceBool::from_usize(self.inner.get_or_init(|| OnceBool::to_usize(f())))
- }
-
- /// 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`.
- pub fn get_or_try_init<F, E>(&self, f: F) -> Result<bool, E>
- where
- F: FnOnce() -> Result<bool, E>,
- {
- self.inner.get_or_try_init(|| f().map(OnceBool::to_usize)).map(OnceBool::from_usize)
- }
-
- #[inline]
- fn from_usize(value: NonZeroUsize) -> bool {
- value.get() == 1
- }
-
- #[inline]
- fn to_usize(value: bool) -> NonZeroUsize {
- unsafe { NonZeroUsize::new_unchecked(if value { 1 } else { 2 }) }
- }
-}
-
-/// A thread-safe cell which can be written to only once.
-pub struct OnceRef<'a, T> {
- inner: AtomicPtr<T>,
- ghost: PhantomData<UnsafeCell<&'a T>>,
-}
-
-// TODO: Replace UnsafeCell with SyncUnsafeCell once stabilized
-unsafe impl<'a, T: Sync> Sync for OnceRef<'a, T> {}
-
-impl<'a, T> core::fmt::Debug for OnceRef<'a, T> {
- fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
- write!(f, "OnceRef({:?})", self.inner)
- }
-}
-
-impl<'a, T> Default for OnceRef<'a, T> {
- fn default() -> Self {
- Self::new()
- }
-}
-
-impl<'a, T> OnceRef<'a, T> {
- /// Creates a new empty cell.
- pub const fn new() -> OnceRef<'a, T> {
- OnceRef { inner: AtomicPtr::new(ptr::null_mut()), ghost: PhantomData }
- }
-
- /// Gets a reference to the underlying value.
- pub fn get(&self) -> Option<&'a T> {
- let ptr = self.inner.load(Ordering::Acquire);
- unsafe { ptr.as_ref() }
- }
-
- /// Sets the contents of this cell to `value`.
- ///
- /// Returns `Ok(())` if the cell was empty and `Err(value)` if it was
- /// full.
- pub fn set(&self, value: &'a T) -> Result<(), ()> {
- let ptr = value as *const T as *mut T;
- let exchange =
- self.inner.compare_exchange(ptr::null_mut(), ptr, Ordering::AcqRel, Ordering::Acquire);
- match exchange {
- Ok(_) => Ok(()),
- Err(_) => Err(()),
- }
- }
-
- /// 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`.
- pub fn get_or_init<F>(&self, f: F) -> &'a T
- where
- F: FnOnce() -> &'a T,
- {
- enum Void {}
- match self.get_or_try_init(|| Ok::<&'a T, Void>(f())) {
- Ok(val) => val,
- Err(void) => match void {},
- }
- }
-
- /// 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`.
- pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&'a T, E>
- where
- F: FnOnce() -> Result<&'a T, E>,
- {
- let mut ptr = self.inner.load(Ordering::Acquire);
-
- if ptr.is_null() {
- // TODO replace with `cast_mut` when MSRV reaches 1.65.0 (also in `set`)
- ptr = f()? as *const T as *mut T;
- let exchange = self.inner.compare_exchange(
- ptr::null_mut(),
- ptr,
- Ordering::AcqRel,
- Ordering::Acquire,
- );
- if let Err(old) = exchange {
- ptr = old;
- }
- }
-
- Ok(unsafe { &*ptr })
- }
-
- /// ```compile_fail
- /// use once_cell::race::OnceRef;
- ///
- /// let mut l = OnceRef::new();
- ///
- /// {
- /// let y = 2;
- /// let mut r = OnceRef::new();
- /// r.set(&y).unwrap();
- /// core::mem::swap(&mut l, &mut r);
- /// }
- ///
- /// // l now contains a dangling reference to y
- /// eprintln!("uaf: {}", l.get().unwrap());
- /// ```
- fn _dummy() {}
-}
-
-#[cfg(feature = "alloc")]
-pub use self::once_box::OnceBox;
-
-#[cfg(feature = "alloc")]
-mod once_box {
- use super::atomic::{AtomicPtr, Ordering};
- use core::{marker::PhantomData, ptr};
-
- use alloc::boxed::Box;
-
- /// A thread-safe cell which can be written to only once.
- pub struct OnceBox<T> {
- inner: AtomicPtr<T>,
- ghost: PhantomData<Option<Box<T>>>,
- }
-
- impl<T> core::fmt::Debug for OnceBox<T> {
- fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
- write!(f, "OnceBox({:?})", self.inner.load(Ordering::Relaxed))
- }
- }
-
- impl<T> Default for OnceBox<T> {
- fn default() -> Self {
- Self::new()
- }
- }
-
- impl<T> Drop for OnceBox<T> {
- fn drop(&mut self) {
- let ptr = *self.inner.get_mut();
- if !ptr.is_null() {
- drop(unsafe { Box::from_raw(ptr) })
- }
- }
- }
-
- impl<T> OnceBox<T> {
- /// Creates a new empty cell.
- pub const fn new() -> OnceBox<T> {
- OnceBox { inner: AtomicPtr::new(ptr::null_mut()), ghost: PhantomData }
- }
-
- /// Gets a reference to the underlying value.
- pub fn get(&self) -> Option<&T> {
- let ptr = self.inner.load(Ordering::Acquire);
- if ptr.is_null() {
- return None;
- }
- Some(unsafe { &*ptr })
- }
-
- /// Sets the contents of this cell to `value`.
- ///
- /// Returns `Ok(())` if the cell was empty and `Err(value)` if it was
- /// full.
- pub fn set(&self, value: Box<T>) -> Result<(), Box<T>> {
- let ptr = Box::into_raw(value);
- let exchange = self.inner.compare_exchange(
- ptr::null_mut(),
- ptr,
- Ordering::AcqRel,
- Ordering::Acquire,
- );
- if exchange.is_err() {
- let value = unsafe { Box::from_raw(ptr) };
- return Err(value);
- }
- Ok(())
- }
-
- /// 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`.
- pub fn get_or_init<F>(&self, f: F) -> &T
- where
- F: FnOnce() -> Box<T>,
- {
- enum Void {}
- match self.get_or_try_init(|| Ok::<Box<T>, Void>(f())) {
- Ok(val) => val,
- Err(void) => match void {},
- }
- }
-
- /// 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`.
- pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E>
- where
- F: FnOnce() -> Result<Box<T>, E>,
- {
- let mut ptr = self.inner.load(Ordering::Acquire);
-
- if ptr.is_null() {
- let val = f()?;
- ptr = Box::into_raw(val);
- let exchange = self.inner.compare_exchange(
- ptr::null_mut(),
- ptr,
- Ordering::AcqRel,
- Ordering::Acquire,
- );
- if let Err(old) = exchange {
- drop(unsafe { Box::from_raw(ptr) });
- ptr = old;
- }
- };
- Ok(unsafe { &*ptr })
- }
- }
-
- unsafe impl<T: Sync + Send> Sync for OnceBox<T> {}
-
- /// ```compile_fail
- /// struct S(*mut ());
- /// unsafe impl Sync for S {}
- ///
- /// fn share<T: Sync>(_: &T) {}
- /// share(&once_cell::race::OnceBox::<S>::new());
- /// ```
- fn _dummy() {}
-}
Copyright © 2024 Valentin A. Popov. All Rights Reverse Engineered.