| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/pin-project-1.1.0/src/lib.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lib.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../pin_project/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../pin_project/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">/*! |
| <!-- tidy:crate-doc:start --> |
| A crate for safe and ergonomic [pin-projection]. |
| |
| ## Usage |
| |
| Add this to your `Cargo.toml`: |
| |
| ```toml |
| [dependencies] |
| pin-project = "1" |
| ``` |
| |
| *Compiler support: requires rustc 1.56+* |
| |
| ## Examples |
| |
| [`#[pin_project]`][`pin_project`] attribute creates projection types |
| covering all the fields of struct or enum. |
| |
| ```rust |
| use std::pin::Pin; |
| |
| use pin_project::pin_project; |
| |
| #[pin_project] |
| struct Struct<T, U> { |
| #[pin] |
| pinned: T, |
| unpinned: U, |
| } |
| |
| impl<T, U> Struct<T, U> { |
| fn method(self: Pin<&mut Self>) { |
| let this = self.project(); |
| let _: Pin<&mut T> = this.pinned; // Pinned reference to the field |
| let _: &mut U = this.unpinned; // Normal reference to the field |
| } |
| } |
| ``` |
| |
| [*code like this will be generated*][struct-default-expanded] |
| |
| To use `#[pin_project]` on enums, you need to name the projection type |
| returned from the method. |
| |
| ```rust |
| use std::pin::Pin; |
| |
| use pin_project::pin_project; |
| |
| #[pin_project(project = EnumProj)] |
| enum Enum<T, U> { |
| Pinned(#[pin] T), |
| Unpinned(U), |
| } |
| |
| impl<T, U> Enum<T, U> { |
| fn method(self: Pin<&mut Self>) { |
| match self.project() { |
| EnumProj::Pinned(x) => { |
| let _: Pin<&mut T> = x; |
| } |
| EnumProj::Unpinned(y) => { |
| let _: &mut U = y; |
| } |
| } |
| } |
| } |
| ``` |
| |
| [*code like this will be generated*][enum-default-expanded] |
| |
| See [`#[pin_project]`][`pin_project`] attribute for more details, and |
| see [examples] directory for more examples and generated code. |
| |
| ## Related Projects |
| |
| - [pin-project-lite]: A lightweight version of pin-project written with declarative macros. |
| |
| [enum-default-expanded]: https://github.com/taiki-e/pin-project/blob/HEAD/examples/enum-default-expanded.rs |
| [examples]: https://github.com/taiki-e/pin-project/blob/HEAD/examples/README.md |
| [pin-project-lite]: https://github.com/taiki-e/pin-project-lite |
| [pin-projection]: https://doc.rust-lang.org/std/pin/index.html#projections-and-structural-pinning |
| [struct-default-expanded]: https://github.com/taiki-e/pin-project/blob/HEAD/examples/struct-default-expanded.rs |
| |
| <!-- tidy:crate-doc:end --> |
| */ |
| |
| </span><span class="attribute">#![no_std] |
| #![doc(test( |
| no_crate_inject, |
| attr( |
| deny(warnings, rust_2018_idioms, single_use_lifetimes), |
| allow(dead_code, unused_variables) |
| ) |
| ))] |
| #![warn(missing_docs, rust_2018_idioms, single_use_lifetimes, unreachable_pub)] |
| #![warn( |
| clippy::pedantic, |
| <span class="comment">// lints for public library |
| </span>clippy::alloc_instead_of_core, |
| clippy::exhaustive_enums, |
| clippy::exhaustive_structs, |
| clippy::std_instead_of_alloc, |
| clippy::std_instead_of_core, |
| <span class="comment">// lints that help writing unsafe code |
| </span>clippy::as_ptr_cast_mut, |
| clippy::default_union_representation, |
| clippy::trailing_empty_array, |
| clippy::transmute_undefined_repr, |
| clippy::undocumented_unsafe_blocks, |
| )] |
| #![allow(clippy::needless_doctest_main)] |
| |
| #[doc(inline)] |
| </span><span class="kw">pub use </span>pin_project_internal::pin_project; |
| <span class="attribute">#[doc(inline)] |
| </span><span class="kw">pub use </span>pin_project_internal::pinned_drop; |
| |
| <span class="doccomment">/// A trait used for custom implementations of [`Unpin`]. |
| /// |
| /// This trait is used in conjunction with the `UnsafeUnpin` argument to |
| /// the [`#[pin_project]`][macro@pin_project] attribute. |
| /// |
| /// # Safety |
| /// |
| /// The Rust [`Unpin`] trait is safe to implement - by itself, |
| /// implementing it cannot lead to [undefined behavior][undefined-behavior]. |
| /// Undefined behavior can only occur when other unsafe code is used. |
| /// |
| /// It turns out that using pin projections, which requires unsafe code, |
| /// imposes additional requirements on an [`Unpin`] impl. Normally, all of this |
| /// unsafety is contained within this crate, ensuring that it's impossible for |
| /// you to violate any of the guarantees required by pin projection. |
| /// |
| /// However, things change if you want to provide a custom [`Unpin`] impl |
| /// for your `#[pin_project]` type. As stated in [the Rust |
| /// documentation][pin-projection], you must be sure to only implement [`Unpin`] |
| /// when all of your `#[pin]` fields (i.e. structurally pinned fields) are also |
| /// [`Unpin`]. |
| /// |
| /// To help highlight this unsafety, the `UnsafeUnpin` trait is provided. |
| /// Implementing this trait is logically equivalent to implementing [`Unpin`] - |
| /// this crate will generate an [`Unpin`] impl for your type that 'forwards' to |
| /// your `UnsafeUnpin` impl. However, this trait is `unsafe` - since your type |
| /// uses structural pinning (otherwise, you wouldn't be using this crate!), |
| /// you must be sure that your `UnsafeUnpin` impls follows all of |
| /// the requirements for an [`Unpin`] impl of a structurally-pinned type. |
| /// |
| /// Note that if you specify `#[pin_project(UnsafeUnpin)]`, but do *not* |
| /// provide an impl of `UnsafeUnpin`, your type will never implement [`Unpin`]. |
| /// This is effectively the same thing as adding a [`PhantomPinned`] to your |
| /// type. |
| /// |
| /// Since this trait is `unsafe`, impls of it will be detected by the |
| /// `unsafe_code` lint, and by tools like [`cargo geiger`][cargo-geiger]. |
| /// |
| /// # Examples |
| /// |
| /// An `UnsafeUnpin` impl which, in addition to requiring that structurally |
| /// pinned fields be [`Unpin`], imposes an additional requirement: |
| /// |
| /// ```rust |
| /// use pin_project::{pin_project, UnsafeUnpin}; |
| /// |
| /// #[pin_project(UnsafeUnpin)] |
| /// struct Struct<K, V> { |
| /// #[pin] |
| /// field_1: K, |
| /// field_2: V, |
| /// } |
| /// |
| /// unsafe impl<K, V> UnsafeUnpin for Struct<K, V> where K: Unpin + Clone {} |
| /// ``` |
| /// |
| /// [`PhantomPinned`]: core::marker::PhantomPinned |
| /// [cargo-geiger]: https://github.com/rust-secure-code/cargo-geiger |
| /// [pin-projection]: core::pin#projections-and-structural-pinning |
| /// [undefined-behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html |
| </span><span class="kw">pub unsafe trait </span>UnsafeUnpin {} |
| |
| <span class="comment">// Not public API. |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub mod </span>__private { |
| <span class="kw">use </span>core::mem::ManuallyDrop; |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub use </span>core::{ |
| marker::{PhantomData, PhantomPinned, Unpin}, |
| ops::Drop, |
| pin::Pin, |
| ptr, |
| }; |
| |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub use </span>pin_project_internal::__PinProjectInternalDerive; |
| |
| <span class="kw">use </span><span class="kw">super</span>::UnsafeUnpin; |
| |
| <span class="comment">// An internal trait used for custom implementations of [`Drop`]. |
| // |
| // **Do not call or implement this trait directly.** |
| // |
| // # Why this trait is private and `#[pinned_drop]` attribute is needed? |
| // |
| // Implementing `PinnedDrop::drop` is safe, but calling it is not safe. |
| // This is because destructors can be called multiple times in safe code and |
| // [double dropping is unsound][rust-lang/rust#62360]. |
| // |
| // Ideally, it would be desirable to be able to forbid manual calls in |
| // the same way as [`Drop::drop`], but the library cannot do it. So, by using |
| // macros and replacing them with private traits, |
| // this crate prevent users from calling `PinnedDrop::drop` in safe code. |
| // |
| // This allows implementing [`Drop`] safely using `#[pinned_drop]`. |
| // Also by using the [`drop`] function just like dropping a type that directly |
| // implements [`Drop`], can drop safely a type that implements `PinnedDrop`. |
| // |
| // [rust-lang/rust#62360]: https://github.com/rust-lang/rust/pull/62360 |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub trait </span>PinnedDrop { |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="kw">unsafe fn </span>drop(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>); |
| } |
| |
| <span class="comment">// This is an internal helper struct used by `pin-project-internal`. |
| // This allows us to force an error if the user tries to provide |
| // a regular `Unpin` impl when they specify the `UnsafeUnpin` argument. |
| // This is why we need Wrapper: |
| // |
| // Supposed we have the following code: |
| // |
| // ```rust |
| // #[pin_project(UnsafeUnpin)] |
| // struct MyStruct<T> { |
| // #[pin] field: T |
| // } |
| // |
| // impl<T> Unpin for MyStruct<T> where MyStruct<T>: UnsafeUnpin {} // generated by pin-project-internal |
| // impl<T> Unpin for MyStruct<T> where T: Copy // written by the user |
| // ``` |
| // |
| // We want this code to be rejected - the user is completely bypassing |
| // `UnsafeUnpin`, and providing an unsound Unpin impl in safe code! |
| // |
| // Unfortunately, the Rust compiler will accept the above code. |
| // Because MyStruct is declared in the same crate as the user-provided impl, |
| // the compiler will notice that `MyStruct<T>: UnsafeUnpin` never holds. |
| // |
| // The solution is to introduce the `Wrapper` struct, which is defined |
| // in the `pin-project` crate. |
| // |
| // We now have code that looks like this: |
| // |
| // ```rust |
| // impl<T> Unpin for MyStruct<T> where Wrapper<MyStruct<T>>: UnsafeUnpin {} // generated by pin-project-internal |
| // impl<T> Unpin for MyStruct<T> where T: Copy // written by the user |
| // ``` |
| // |
| // We also have `unsafe impl<T> UnsafeUnpin for Wrapper<T> where T: UnsafeUnpin {}` |
| // in the `pin-project` crate. |
| // |
| // Now, our generated impl has a bound involving a type defined in another |
| // crate - Wrapper. This will cause rust to conservatively assume that |
| // `Wrapper<MyStruct<T>>: UnsafeUnpin` holds, in the interest of preserving |
| // forwards compatibility (in case such an impl is added for Wrapper<T> in |
| // a new version of the crate). |
| // |
| // This will cause rust to reject any other `Unpin` impls for MyStruct<T>, |
| // since it will assume that our generated impl could potentially apply in |
| // any situation. |
| // |
| // This achieves the desired effect - when the user writes |
| // `#[pin_project(UnsafeUnpin)]`, the user must either provide no impl of |
| // `UnsafeUnpin` (which is equivalent to making the type never implement |
| // Unpin), or provide an impl of `UnsafeUnpin`. It is impossible for them to |
| // provide an impl of `Unpin` |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub struct </span>Wrapper<<span class="lifetime">'a</span>, T: <span class="question-mark">?</span>Sized>(PhantomData<<span class="kw-2">&</span><span class="lifetime">'a </span>()>, T); |
| |
| <span class="comment">// SAFETY: `T` implements UnsafeUnpin. |
| </span><span class="kw">unsafe impl</span><T: <span class="question-mark">?</span>Sized + UnsafeUnpin> UnsafeUnpin <span class="kw">for </span>Wrapper<<span class="lifetime">'_</span>, T> {} |
| |
| <span class="comment">// This is an internal helper struct used by `pin-project-internal`. |
| // |
| // See https://github.com/taiki-e/pin-project/pull/53 for more details. |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub struct </span>AlwaysUnpin<<span class="lifetime">'a</span>, T>(PhantomData<<span class="kw-2">&</span><span class="lifetime">'a </span>()>, PhantomData<T>); |
| |
| <span class="kw">impl</span><T> Unpin <span class="kw">for </span>AlwaysUnpin<<span class="lifetime">'_</span>, T> {} |
| |
| <span class="comment">// This is an internal helper used to ensure a value is dropped. |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub struct </span>UnsafeDropInPlaceGuard<T: <span class="question-mark">?</span>Sized>(<span class="kw-2">*mut </span>T); |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized> UnsafeDropInPlaceGuard<T> { |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub unsafe fn </span>new(ptr: <span class="kw-2">*mut </span>T) -> <span class="self">Self </span>{ |
| <span class="self">Self</span>(ptr) |
| } |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized> Drop <span class="kw">for </span>UnsafeDropInPlaceGuard<T> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="comment">// SAFETY: the caller of `UnsafeDropInPlaceGuard::new` must guarantee |
| // that `ptr` is valid for drop when this guard is destructed. |
| </span><span class="kw">unsafe </span>{ |
| ptr::drop_in_place(<span class="self">self</span>.<span class="number">0</span>); |
| } |
| } |
| } |
| |
| <span class="comment">// This is an internal helper used to ensure a value is overwritten without |
| // its destructor being called. |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub struct </span>UnsafeOverwriteGuard<T> { |
| target: <span class="kw-2">*mut </span>T, |
| value: ManuallyDrop<T>, |
| } |
| |
| <span class="kw">impl</span><T> UnsafeOverwriteGuard<T> { |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub unsafe fn </span>new(target: <span class="kw-2">*mut </span>T, value: T) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ target, value: ManuallyDrop::new(value) } |
| } |
| } |
| |
| <span class="kw">impl</span><T> Drop <span class="kw">for </span>UnsafeOverwriteGuard<T> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="comment">// SAFETY: the caller of `UnsafeOverwriteGuard::new` must guarantee |
| // that `target` is valid for writes when this guard is destructed. |
| </span><span class="kw">unsafe </span>{ |
| ptr::write(<span class="self">self</span>.target, ptr::read(<span class="kw-2">&*</span><span class="self">self</span>.value)); |
| } |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="pin_project" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
