From 8cdfa445d6629ffef4cb84967ff7017654045bc2 Mon Sep 17 00:00:00 2001 From: mo khan Date: Wed, 2 Jul 2025 18:36:06 -0600 Subject: chore: add vendor directory --- vendor/sync_wrapper/src/lib.rs | 258 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 258 insertions(+) create mode 100644 vendor/sync_wrapper/src/lib.rs (limited to 'vendor/sync_wrapper/src') diff --git a/vendor/sync_wrapper/src/lib.rs b/vendor/sync_wrapper/src/lib.rs new file mode 100644 index 00000000..a508e2ff --- /dev/null +++ b/vendor/sync_wrapper/src/lib.rs @@ -0,0 +1,258 @@ +/* + * Copyright 2020 Actyx AG + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +//! A mutual exclusion primitive that relies on static type information only +//! +//! This library is inspired by [this discussion](https://internals.rust-lang.org/t/what-shall-sync-mean-across-an-await/12020/2). +#![doc(html_logo_url = "https://developer.actyx.com/img/logo.svg")] +#![doc(html_favicon_url = "https://developer.actyx.com/img/favicon.ico")] +#![no_std] + +use core::{ + fmt::{self, Debug, Formatter}, + pin::Pin, + future::Future, + task::{Context, Poll}, +}; + +/// A mutual exclusion primitive that relies on static type information only +/// +/// In some cases synchronization can be proven statically: whenever you hold an exclusive `&mut` +/// reference, the Rust type system ensures that no other part of the program can hold another +/// reference to the data. Therefore it is safe to access it even if the current thread obtained +/// this reference via a channel. Whenever this is the case, the overhead of allocating and locking +/// a [`Mutex`] can be avoided by using this static version. +/// +/// One example where this is often applicable is [`Future`], which requires an exclusive reference +/// for its [`poll`] method: While a given `Future` implementation may not be safe to access by +/// multiple threads concurrently, the executor can only run the `Future` on one thread at any +/// given time, making it [`Sync`] in practice as long as the implementation is `Send`. You can +/// therefore use the static mutex to prove that your data structure is `Sync` even though it +/// contains such a `Future`. +/// +/// # Example +/// +/// ``` +/// use sync_wrapper::SyncWrapper; +/// use std::future::Future; +/// +/// struct MyThing { +/// future: SyncWrapper + Send>>, +/// } +/// +/// impl MyThing { +/// // all accesses to `self.future` now require an exclusive reference or ownership +/// } +/// +/// fn assert_sync() {} +/// +/// assert_sync::(); +/// ``` +/// +/// [`Mutex`]: https://doc.rust-lang.org/std/sync/struct.Mutex.html +/// [`Future`]: https://doc.rust-lang.org/std/future/trait.Future.html +/// [`poll`]: https://doc.rust-lang.org/std/future/trait.Future.html#method.poll +/// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html +#[repr(transparent)] +pub struct SyncWrapper(T); + +impl SyncWrapper { + /// Creates a new static mutex containing the given value. + /// + /// # Examples + /// + /// ``` + /// use sync_wrapper::SyncWrapper; + /// + /// let mutex = SyncWrapper::new(42); + /// ``` + pub const fn new(value: T) -> Self { + Self(value) + } + + /// Acquires a reference to the protected value. + /// + /// This is safe because it requires an exclusive reference to the mutex. Therefore this method + /// neither panics nor does it return an error. This is in contrast to [`Mutex::get_mut`] which + /// returns an error if another thread panicked while holding the lock. It is not recommended + /// to send an exclusive reference to a potentially damaged value to another thread for further + /// processing. + /// + /// [`Mutex::get_mut`]: https://doc.rust-lang.org/std/sync/struct.Mutex.html#method.get_mut + /// + /// # Examples + /// + /// ``` + /// use sync_wrapper::SyncWrapper; + /// + /// let mut mutex = SyncWrapper::new(42); + /// let value = mutex.get_mut(); + /// *value = 0; + /// assert_eq!(*mutex.get_mut(), 0); + /// ``` + pub fn get_mut(&mut self) -> &mut T { + &mut self.0 + } + + /// Acquires a pinned reference to the protected value. + /// + /// See [`Self::get_mut`] for why this method is safe. + /// + /// # Examples + /// + /// ``` + /// use std::future::Future; + /// use std::pin::Pin; + /// use std::task::{Context, Poll}; + /// + /// use pin_project_lite::pin_project; + /// use sync_wrapper::SyncWrapper; + /// + /// pin_project! { + /// struct FutureWrapper { + /// #[pin] + /// inner: SyncWrapper, + /// } + /// } + /// + /// impl Future for FutureWrapper { + /// type Output = F::Output; + /// + /// fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll { + /// self.project().inner.get_pin_mut().poll(cx) + /// } + /// } + /// ``` + pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut T> { + unsafe { Pin::map_unchecked_mut(self, |this| &mut this.0) } + } + + /// Consumes this mutex, returning the underlying data. + /// + /// This is safe because it requires ownership of the mutex, therefore this method will neither + /// panic nor does it return an error. This is in contrast to [`Mutex::into_inner`] which + /// returns an error if another thread panicked while holding the lock. It is not recommended + /// to send an exclusive reference to a potentially damaged value to another thread for further + /// processing. + /// + /// [`Mutex::into_inner`]: https://doc.rust-lang.org/std/sync/struct.Mutex.html#method.into_inner + /// + /// # Examples + /// + /// ``` + /// use sync_wrapper::SyncWrapper; + /// + /// let mut mutex = SyncWrapper::new(42); + /// assert_eq!(mutex.into_inner(), 42); + /// ``` + pub fn into_inner(self) -> T { + self.0 + } +} + +// this is safe because the only operations permitted on this data structure require exclusive +// access or ownership +unsafe impl Sync for SyncWrapper {} + +impl Debug for SyncWrapper { + fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result { + f.pad("SyncWrapper") + } +} + +impl Default for SyncWrapper { + fn default() -> Self { + Self::new(T::default()) + } +} + +impl From for SyncWrapper { + fn from(value: T) -> Self { + Self::new(value) + } +} + +/// `Future` which is `Sync`. +/// +/// # Examples +/// +/// ``` +/// use sync_wrapper::{SyncWrapper, SyncFuture}; +/// +/// let fut = async { 1 }; +/// let fut = SyncFuture::new(fut); +/// ``` +pub struct SyncFuture { + inner: SyncWrapper +} +impl SyncFuture { + pub fn new(inner: F) -> Self { + Self { inner: SyncWrapper::new(inner) } + } + pub fn into_inner(self) -> F { + self.inner.into_inner() + } +} +impl Future for SyncFuture { + type Output = F::Output; + fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll { + let inner = unsafe { self.map_unchecked_mut(|x| x.inner.get_mut()) }; + inner.poll(cx) + } +} +impl Debug for SyncFuture { + fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result { + f.pad("SyncFuture") + } +} + +/// `Stream` which is `Sync`. +/// +/// # Examples +/// +/// ``` +/// use sync_wrapper::SyncStream; +/// use futures::stream; +/// +/// let st = stream::iter(vec![1]); +/// let st = SyncStream::new(st); +/// ``` +#[cfg(feature = "futures")] +pub struct SyncStream { + inner: SyncWrapper +} +#[cfg(feature = "futures")] +impl SyncStream { + pub fn new(inner: S) -> Self { + Self { inner: SyncWrapper::new(inner) } + } + pub fn into_inner(self) -> S { + self.inner.into_inner() + } +} +#[cfg(feature = "futures")] +impl futures_core::Stream for SyncStream { + type Item = S::Item; + fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll> { + let inner = unsafe { self.map_unchecked_mut(|x| x.inner.get_mut()) }; + inner.poll_next(cx) + } +} +#[cfg(feature = "futures")] +impl Debug for SyncStream { + fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result { + f.pad("SyncStream") + } +} -- cgit v1.2.3