--- /dev/null
- // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).
+ // SPDX-License-Identifier: Apache-2.0 OR MIT
+
+ //! Library to safely and fallibly initialize pinned `struct`s using in-place constructors.
+ //!
+ //! [Pinning][pinning] is Rust's way of ensuring data does not move.
+ //!
+ //! It also allows in-place initialization of big `struct`s that would otherwise produce a stack
+ //! overflow.
+ //!
+ //! This library's main use-case is in [Rust-for-Linux]. Although this version can be used
+ //! standalone.
+ //!
+ //! There are cases when you want to in-place initialize a struct. For example when it is very big
+ //! and moving it from the stack is not an option, because it is bigger than the stack itself.
+ //! Another reason would be that you need the address of the object to initialize it. This stands
+ //! in direct conflict with Rust's normal process of first initializing an object and then moving
+ //! it into it's final memory location. For more information, see
+ //! <https://rust-for-linux.com/the-safe-pinned-initialization-problem>.
+ //!
+ //! This library allows you to do in-place initialization safely.
+ //!
+ //! ## Nightly Needed for `alloc` feature
+ //!
+ //! This library requires the [`allocator_api` unstable feature] when the `alloc` feature is
+ //! enabled and thus this feature can only be used with a nightly compiler. When enabling the
+ //! `alloc` feature, the user will be required to activate `allocator_api` as well.
+ //!
+ //! [`allocator_api` unstable feature]: https://doc.rust-lang.org/nightly/unstable-book/library-features/allocator-api.html
+ //!
+ //! The feature is enabled by default, thus by default `pin-init` will require a nightly compiler.
+ //! However, using the crate on stable compilers is possible by disabling `alloc`. In practice this
+ //! will require the `std` feature, because stable compilers have neither `Box` nor `Arc` in no-std
+ //! mode.
+ //!
+ //! # Overview
+ //!
+ //! To initialize a `struct` with an in-place constructor you will need two things:
+ //! - an in-place constructor,
+ //! - a memory location that can hold your `struct` (this can be the [stack], an [`Arc<T>`],
+ //! [`Box<T>`] or any other smart pointer that supports this library).
+ //!
+ //! To get an in-place constructor there are generally three options:
+ //! - directly creating an in-place constructor using the [`pin_init!`] macro,
+ //! - a custom function/macro returning an in-place constructor provided by someone else,
+ //! - using the unsafe function [`pin_init_from_closure()`] to manually create an initializer.
+ //!
+ //! Aside from pinned initialization, this library also supports in-place construction without
+ //! pinning, the macros/types/functions are generally named like the pinned variants without the
+ //! `pin_` prefix.
+ //!
+ //! # Examples
+ //!
+ //! Throughout the examples we will often make use of the `CMutex` type which can be found in
+ //! `../examples/mutex.rs`. It is essentially a userland rebuild of the `struct mutex` type from
+ //! the Linux kernel. It also uses a wait list and a basic spinlock. Importantly the wait list
+ //! requires it to be pinned to be locked and thus is a prime candidate for using this library.
+ //!
+ //! ## Using the [`pin_init!`] macro
+ //!
+ //! If you want to use [`PinInit`], then you will have to annotate your `struct` with
+ //! `#[`[`pin_data`]`]`. It is a macro that uses `#[pin]` as a marker for
+ //! [structurally pinned fields]. After doing this, you can then create an in-place constructor via
+ //! [`pin_init!`]. The syntax is almost the same as normal `struct` initializers. The difference is
+ //! that you need to write `<-` instead of `:` for fields that you want to initialize in-place.
+ //!
+ //! ```rust
+ //! # #![expect(clippy::disallowed_names)]
+ //! # #![feature(allocator_api)]
+ //! # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ //! # use core::pin::Pin;
+ //! use pin_init::{pin_data, pin_init, InPlaceInit};
+ //!
+ //! #[pin_data]
+ //! struct Foo {
+ //! #[pin]
+ //! a: CMutex<usize>,
+ //! b: u32,
+ //! }
+ //!
+ //! let foo = pin_init!(Foo {
+ //! a <- CMutex::new(42),
+ //! b: 24,
+ //! });
+ //! # let _ = Box::pin_init(foo);
+ //! ```
+ //!
+ //! `foo` now is of the type [`impl PinInit<Foo>`]. We can now use any smart pointer that we like
+ //! (or just the stack) to actually initialize a `Foo`:
+ //!
+ //! ```rust
+ //! # #![expect(clippy::disallowed_names)]
+ //! # #![feature(allocator_api)]
+ //! # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ //! # use core::{alloc::AllocError, pin::Pin};
+ //! # use pin_init::*;
+ //! #
+ //! # #[pin_data]
+ //! # struct Foo {
+ //! # #[pin]
+ //! # a: CMutex<usize>,
+ //! # b: u32,
+ //! # }
+ //! #
+ //! # let foo = pin_init!(Foo {
+ //! # a <- CMutex::new(42),
+ //! # b: 24,
+ //! # });
+ //! let foo: Result<Pin<Box<Foo>>, AllocError> = Box::pin_init(foo);
+ //! ```
+ //!
+ //! For more information see the [`pin_init!`] macro.
+ //!
+ //! ## Using a custom function/macro that returns an initializer
+ //!
+ //! Many types that use this library supply a function/macro that returns an initializer, because
+ //! the above method only works for types where you can access the fields.
+ //!
+ //! ```rust
+ //! # #![feature(allocator_api)]
+ //! # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ //! # use pin_init::*;
+ //! # use std::sync::Arc;
+ //! # use core::pin::Pin;
+ //! let mtx: Result<Pin<Arc<CMutex<usize>>>, _> = Arc::pin_init(CMutex::new(42));
+ //! ```
+ //!
+ //! To declare an init macro/function you just return an [`impl PinInit<T, E>`]:
+ //!
+ //! ```rust
+ //! # #![feature(allocator_api)]
+ //! # use pin_init::*;
+ //! # #[path = "../examples/error.rs"] mod error; use error::Error;
+ //! # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ //! #[pin_data]
+ //! struct DriverData {
+ //! #[pin]
+ //! status: CMutex<i32>,
+ //! buffer: Box<[u8; 1_000_000]>,
+ //! }
+ //!
+ //! impl DriverData {
+ //! fn new() -> impl PinInit<Self, Error> {
+ //! try_pin_init!(Self {
+ //! status <- CMutex::new(0),
+ //! buffer: Box::init(pin_init::zeroed())?,
+ //! }? Error)
+ //! }
+ //! }
+ //! ```
+ //!
+ //! ## Manual creation of an initializer
+ //!
+ //! Often when working with primitives the previous approaches are not sufficient. That is where
+ //! [`pin_init_from_closure()`] comes in. This `unsafe` function allows you to create a
+ //! [`impl PinInit<T, E>`] directly from a closure. Of course you have to ensure that the closure
+ //! actually does the initialization in the correct way. Here are the things to look out for
+ //! (we are calling the parameter to the closure `slot`):
+ //! - when the closure returns `Ok(())`, then it has completed the initialization successfully, so
+ //! `slot` now contains a valid bit pattern for the type `T`,
+ //! - when the closure returns `Err(e)`, then the caller may deallocate the memory at `slot`, so
+ //! you need to take care to clean up anything if your initialization fails mid-way,
+ //! - you may assume that `slot` will stay pinned even after the closure returns until `drop` of
+ //! `slot` gets called.
+ //!
+ //! ```rust
+ //! # #![feature(extern_types)]
+ //! use pin_init::{pin_data, pinned_drop, PinInit, PinnedDrop, pin_init_from_closure};
+ //! use core::{
+ //! ptr::addr_of_mut,
+ //! marker::PhantomPinned,
+ //! cell::UnsafeCell,
+ //! pin::Pin,
+ //! mem::MaybeUninit,
+ //! };
+ //! mod bindings {
+ //! #[repr(C)]
+ //! pub struct foo {
+ //! /* fields from C ... */
+ //! }
+ //! extern "C" {
+ //! pub fn init_foo(ptr: *mut foo);
+ //! pub fn destroy_foo(ptr: *mut foo);
+ //! #[must_use = "you must check the error return code"]
+ //! pub fn enable_foo(ptr: *mut foo, flags: u32) -> i32;
+ //! }
+ //! }
+ //!
+ //! /// # Invariants
+ //! ///
+ //! /// `foo` is always initialized
+ //! #[pin_data(PinnedDrop)]
+ //! pub struct RawFoo {
+ //! #[pin]
+ //! _p: PhantomPinned,
+ //! #[pin]
+ //! foo: UnsafeCell<MaybeUninit<bindings::foo>>,
+ //! }
+ //!
+ //! impl RawFoo {
+ //! pub fn new(flags: u32) -> impl PinInit<Self, i32> {
+ //! // SAFETY:
+ //! // - when the closure returns `Ok(())`, then it has successfully initialized and
+ //! // enabled `foo`,
+ //! // - when it returns `Err(e)`, then it has cleaned up before
+ //! unsafe {
+ //! pin_init_from_closure(move |slot: *mut Self| {
+ //! // `slot` contains uninit memory, avoid creating a reference.
+ //! let foo = addr_of_mut!((*slot).foo);
+ //! let foo = UnsafeCell::raw_get(foo).cast::<bindings::foo>();
+ //!
+ //! // Initialize the `foo`
+ //! bindings::init_foo(foo);
+ //!
+ //! // Try to enable it.
+ //! let err = bindings::enable_foo(foo, flags);
+ //! if err != 0 {
+ //! // Enabling has failed, first clean up the foo and then return the error.
+ //! bindings::destroy_foo(foo);
+ //! Err(err)
+ //! } else {
+ //! // All fields of `RawFoo` have been initialized, since `_p` is a ZST.
+ //! Ok(())
+ //! }
+ //! })
+ //! }
+ //! }
+ //! }
+ //!
+ //! #[pinned_drop]
+ //! impl PinnedDrop for RawFoo {
+ //! fn drop(self: Pin<&mut Self>) {
+ //! // SAFETY: Since `foo` is initialized, destroying is safe.
+ //! unsafe { bindings::destroy_foo(self.foo.get().cast::<bindings::foo>()) };
+ //! }
+ //! }
+ //! ```
+ //!
+ //! For more information on how to use [`pin_init_from_closure()`], take a look at the uses inside
+ //! the `kernel` crate. The [`sync`] module is a good starting point.
+ //!
+ //! [`sync`]: https://rust.docs.kernel.org/kernel/sync/index.html
+ //! [pinning]: https://doc.rust-lang.org/std/pin/index.html
+ //! [structurally pinned fields]:
+ //! https://doc.rust-lang.org/std/pin/index.html#pinning-is-structural-for-field
+ //! [stack]: crate::stack_pin_init
+ #![cfg_attr(
+ kernel,
+ doc = "[`Arc<T>`]: https://rust.docs.kernel.org/kernel/sync/struct.Arc.html"
+ )]
+ #![cfg_attr(
+ kernel,
+ doc = "[`Box<T>`]: https://rust.docs.kernel.org/kernel/alloc/kbox/struct.Box.html"
+ )]
+ #![cfg_attr(not(kernel), doc = "[`Arc<T>`]: alloc::alloc::sync::Arc")]
+ #![cfg_attr(not(kernel), doc = "[`Box<T>`]: alloc::alloc::boxed::Box")]
+ //! [`impl PinInit<Foo>`]: crate::PinInit
+ //! [`impl PinInit<T, E>`]: crate::PinInit
+ //! [`impl Init<T, E>`]: crate::Init
+ //! [Rust-for-Linux]: https://rust-for-linux.com/
+
+ #![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
+ #![cfg_attr(
+ all(
+ any(feature = "alloc", feature = "std"),
+ not(RUSTC_NEW_UNINIT_IS_STABLE)
+ ),
+ feature(new_uninit)
+ )]
+ #![forbid(missing_docs, unsafe_op_in_unsafe_fn)]
+ #![cfg_attr(not(feature = "std"), no_std)]
+ #![cfg_attr(feature = "alloc", feature(allocator_api))]
+
+ use core::{
+ cell::UnsafeCell,
+ convert::Infallible,
+ marker::PhantomData,
+ mem::MaybeUninit,
+ num::*,
+ pin::Pin,
+ ptr::{self, NonNull},
+ };
+
+ #[doc(hidden)]
+ pub mod __internal;
+ #[doc(hidden)]
+ pub mod macros;
+
+ #[cfg(any(feature = "std", feature = "alloc"))]
+ mod alloc;
+ #[cfg(any(feature = "std", feature = "alloc"))]
+ pub use alloc::InPlaceInit;
+
+ /// Used to specify the pinning information of the fields of a struct.
+ ///
+ /// This is somewhat similar in purpose as
+ /// [pin-project-lite](https://crates.io/crates/pin-project-lite).
+ /// Place this macro on a struct definition and then `#[pin]` in front of the attributes of each
+ /// field you want to structurally pin.
+ ///
+ /// This macro enables the use of the [`pin_init!`] macro. When pin-initializing a `struct`,
+ /// then `#[pin]` directs the type of initializer that is required.
+ ///
+ /// If your `struct` implements `Drop`, then you need to add `PinnedDrop` as arguments to this
+ /// macro, and change your `Drop` implementation to `PinnedDrop` annotated with
+ /// `#[`[`macro@pinned_drop`]`]`, since dropping pinned values requires extra care.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// use pin_init::pin_data;
+ ///
+ /// enum Command {
+ /// /* ... */
+ /// }
+ ///
+ /// #[pin_data]
+ /// struct DriverData {
+ /// #[pin]
+ /// queue: CMutex<Vec<Command>>,
+ /// buf: Box<[u8; 1024 * 1024]>,
+ /// }
+ /// ```
+ ///
+ /// ```
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # mod bindings { pub struct info; pub unsafe fn destroy_info(_: *mut info) {} }
+ /// use core::pin::Pin;
+ /// use pin_init::{pin_data, pinned_drop, PinnedDrop};
+ ///
+ /// enum Command {
+ /// /* ... */
+ /// }
+ ///
+ /// #[pin_data(PinnedDrop)]
+ /// struct DriverData {
+ /// #[pin]
+ /// queue: CMutex<Vec<Command>>,
+ /// buf: Box<[u8; 1024 * 1024]>,
+ /// raw_info: *mut bindings::info,
+ /// }
+ ///
+ /// #[pinned_drop]
+ /// impl PinnedDrop for DriverData {
+ /// fn drop(self: Pin<&mut Self>) {
+ /// unsafe { bindings::destroy_info(self.raw_info) };
+ /// }
+ /// }
+ /// ```
+ pub use ::pin_init_internal::pin_data;
+
+ /// Used to implement `PinnedDrop` safely.
+ ///
+ /// Only works on structs that are annotated via `#[`[`macro@pin_data`]`]`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # mod bindings { pub struct info; pub unsafe fn destroy_info(_: *mut info) {} }
+ /// use core::pin::Pin;
+ /// use pin_init::{pin_data, pinned_drop, PinnedDrop};
+ ///
+ /// enum Command {
+ /// /* ... */
+ /// }
+ ///
+ /// #[pin_data(PinnedDrop)]
+ /// struct DriverData {
+ /// #[pin]
+ /// queue: CMutex<Vec<Command>>,
+ /// buf: Box<[u8; 1024 * 1024]>,
+ /// raw_info: *mut bindings::info,
+ /// }
+ ///
+ /// #[pinned_drop]
+ /// impl PinnedDrop for DriverData {
+ /// fn drop(self: Pin<&mut Self>) {
+ /// unsafe { bindings::destroy_info(self.raw_info) };
+ /// }
+ /// }
+ /// ```
+ pub use ::pin_init_internal::pinned_drop;
+
+ /// Derives the [`Zeroable`] trait for the given struct.
+ ///
+ /// This can only be used for structs where every field implements the [`Zeroable`] trait.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use pin_init::Zeroable;
+ ///
+ /// #[derive(Zeroable)]
+ /// pub struct DriverData {
+ /// id: i64,
+ /// buf_ptr: *mut u8,
+ /// len: usize,
+ /// }
+ /// ```
+ pub use ::pin_init_internal::Zeroable;
+
+ /// Initialize and pin a type directly on the stack.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![expect(clippy::disallowed_names)]
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # use pin_init::*;
+ /// # use core::pin::Pin;
+ /// #[pin_data]
+ /// struct Foo {
+ /// #[pin]
+ /// a: CMutex<usize>,
+ /// b: Bar,
+ /// }
+ ///
+ /// #[pin_data]
+ /// struct Bar {
+ /// x: u32,
+ /// }
+ ///
+ /// stack_pin_init!(let foo = pin_init!(Foo {
+ /// a <- CMutex::new(42),
+ /// b: Bar {
+ /// x: 64,
+ /// },
+ /// }));
+ /// let foo: Pin<&mut Foo> = foo;
+ /// println!("a: {}", &*foo.a.lock());
+ /// ```
+ ///
+ /// # Syntax
+ ///
+ /// A normal `let` binding with optional type annotation. The expression is expected to implement
+ /// [`PinInit`]/[`Init`] with the error type [`Infallible`]. If you want to use a different error
+ /// type, then use [`stack_try_pin_init!`].
+ #[macro_export]
+ macro_rules! stack_pin_init {
+ (let $var:ident $(: $t:ty)? = $val:expr) => {
+ let val = $val;
+ let mut $var = ::core::pin::pin!($crate::__internal::StackInit$(::<$t>)?::uninit());
+ let mut $var = match $crate::__internal::StackInit::init($var, val) {
+ Ok(res) => res,
+ Err(x) => {
+ let x: ::core::convert::Infallible = x;
+ match x {}
+ }
+ };
+ };
+ }
+
+ /// Initialize and pin a type directly on the stack.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![expect(clippy::disallowed_names)]
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/error.rs"] mod error; use error::Error;
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # use pin_init::*;
+ /// #[pin_data]
+ /// struct Foo {
+ /// #[pin]
+ /// a: CMutex<usize>,
+ /// b: Box<Bar>,
+ /// }
+ ///
+ /// struct Bar {
+ /// x: u32,
+ /// }
+ ///
+ /// stack_try_pin_init!(let foo: Foo = try_pin_init!(Foo {
+ /// a <- CMutex::new(42),
+ /// b: Box::try_new(Bar {
+ /// x: 64,
+ /// })?,
+ /// }? Error));
+ /// let foo = foo.unwrap();
+ /// println!("a: {}", &*foo.a.lock());
+ /// ```
+ ///
+ /// ```rust
+ /// # #![expect(clippy::disallowed_names)]
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/error.rs"] mod error; use error::Error;
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # use pin_init::*;
+ /// #[pin_data]
+ /// struct Foo {
+ /// #[pin]
+ /// a: CMutex<usize>,
+ /// b: Box<Bar>,
+ /// }
+ ///
+ /// struct Bar {
+ /// x: u32,
+ /// }
+ ///
+ /// stack_try_pin_init!(let foo: Foo =? try_pin_init!(Foo {
+ /// a <- CMutex::new(42),
+ /// b: Box::try_new(Bar {
+ /// x: 64,
+ /// })?,
+ /// }? Error));
+ /// println!("a: {}", &*foo.a.lock());
+ /// # Ok::<_, Error>(())
+ /// ```
+ ///
+ /// # Syntax
+ ///
+ /// A normal `let` binding with optional type annotation. The expression is expected to implement
+ /// [`PinInit`]/[`Init`]. This macro assigns a result to the given variable, adding a `?` after the
+ /// `=` will propagate this error.
+ #[macro_export]
+ macro_rules! stack_try_pin_init {
+ (let $var:ident $(: $t:ty)? = $val:expr) => {
+ let val = $val;
+ let mut $var = ::core::pin::pin!($crate::__internal::StackInit$(::<$t>)?::uninit());
+ let mut $var = $crate::__internal::StackInit::init($var, val);
+ };
+ (let $var:ident $(: $t:ty)? =? $val:expr) => {
+ let val = $val;
+ let mut $var = ::core::pin::pin!($crate::__internal::StackInit$(::<$t>)?::uninit());
+ let mut $var = $crate::__internal::StackInit::init($var, val)?;
+ };
+ }
+
+ /// Construct an in-place, pinned initializer for `struct`s.
+ ///
+ /// This macro defaults the error to [`Infallible`]. If you need a different error, then use
+ /// [`try_pin_init!`].
+ ///
+ /// The syntax is almost identical to that of a normal `struct` initializer:
+ ///
+ /// ```rust
+ /// # use pin_init::*;
+ /// # use core::pin::Pin;
+ /// #[pin_data]
+ /// struct Foo {
+ /// a: usize,
+ /// b: Bar,
+ /// }
+ ///
+ /// #[pin_data]
+ /// struct Bar {
+ /// x: u32,
+ /// }
+ ///
+ /// # fn demo() -> impl PinInit<Foo> {
+ /// let a = 42;
+ ///
+ /// let initializer = pin_init!(Foo {
+ /// a,
+ /// b: Bar {
+ /// x: 64,
+ /// },
+ /// });
+ /// # initializer }
+ /// # Box::pin_init(demo()).unwrap();
+ /// ```
+ ///
+ /// Arbitrary Rust expressions can be used to set the value of a variable.
+ ///
+ /// The fields are initialized in the order that they appear in the initializer. So it is possible
+ /// to read already initialized fields using raw pointers.
+ ///
+ /// IMPORTANT: You are not allowed to create references to fields of the struct inside of the
+ /// initializer.
+ ///
+ /// # Init-functions
+ ///
+ /// When working with this library it is often desired to let others construct your types without
+ /// giving access to all fields. This is where you would normally write a plain function `new` that
+ /// would return a new instance of your type. With this library that is also possible. However,
+ /// there are a few extra things to keep in mind.
+ ///
+ /// To create an initializer function, simply declare it like this:
+ ///
+ /// ```rust
+ /// # use pin_init::*;
+ /// # use core::pin::Pin;
+ /// # #[pin_data]
+ /// # struct Foo {
+ /// # a: usize,
+ /// # b: Bar,
+ /// # }
+ /// # #[pin_data]
+ /// # struct Bar {
+ /// # x: u32,
+ /// # }
+ /// impl Foo {
+ /// fn new() -> impl PinInit<Self> {
+ /// pin_init!(Self {
+ /// a: 42,
+ /// b: Bar {
+ /// x: 64,
+ /// },
+ /// })
+ /// }
+ /// }
+ /// ```
+ ///
+ /// Users of `Foo` can now create it like this:
+ ///
+ /// ```rust
+ /// # #![expect(clippy::disallowed_names)]
+ /// # use pin_init::*;
+ /// # use core::pin::Pin;
+ /// # #[pin_data]
+ /// # struct Foo {
+ /// # a: usize,
+ /// # b: Bar,
+ /// # }
+ /// # #[pin_data]
+ /// # struct Bar {
+ /// # x: u32,
+ /// # }
+ /// # impl Foo {
+ /// # fn new() -> impl PinInit<Self> {
+ /// # pin_init!(Self {
+ /// # a: 42,
+ /// # b: Bar {
+ /// # x: 64,
+ /// # },
+ /// # })
+ /// # }
+ /// # }
+ /// let foo = Box::pin_init(Foo::new());
+ /// ```
+ ///
+ /// They can also easily embed it into their own `struct`s:
+ ///
+ /// ```rust
+ /// # use pin_init::*;
+ /// # use core::pin::Pin;
+ /// # #[pin_data]
+ /// # struct Foo {
+ /// # a: usize,
+ /// # b: Bar,
+ /// # }
+ /// # #[pin_data]
+ /// # struct Bar {
+ /// # x: u32,
+ /// # }
+ /// # impl Foo {
+ /// # fn new() -> impl PinInit<Self> {
+ /// # pin_init!(Self {
+ /// # a: 42,
+ /// # b: Bar {
+ /// # x: 64,
+ /// # },
+ /// # })
+ /// # }
+ /// # }
+ /// #[pin_data]
+ /// struct FooContainer {
+ /// #[pin]
+ /// foo1: Foo,
+ /// #[pin]
+ /// foo2: Foo,
+ /// other: u32,
+ /// }
+ ///
+ /// impl FooContainer {
+ /// fn new(other: u32) -> impl PinInit<Self> {
+ /// pin_init!(Self {
+ /// foo1 <- Foo::new(),
+ /// foo2 <- Foo::new(),
+ /// other,
+ /// })
+ /// }
+ /// }
+ /// ```
+ ///
+ /// Here we see that when using `pin_init!` with `PinInit`, one needs to write `<-` instead of `:`.
+ /// This signifies that the given field is initialized in-place. As with `struct` initializers, just
+ /// writing the field (in this case `other`) without `:` or `<-` means `other: other,`.
+ ///
+ /// # Syntax
+ ///
+ /// As already mentioned in the examples above, inside of `pin_init!` a `struct` initializer with
+ /// the following modifications is expected:
+ /// - Fields that you want to initialize in-place have to use `<-` instead of `:`.
+ /// - In front of the initializer you can write `&this in` to have access to a [`NonNull<Self>`]
+ /// pointer named `this` inside of the initializer.
+ /// - Using struct update syntax one can place `..Zeroable::zeroed()` at the very end of the
+ /// struct, this initializes every field with 0 and then runs all initializers specified in the
+ /// body. This can only be done if [`Zeroable`] is implemented for the struct.
+ ///
+ /// For instance:
+ ///
+ /// ```rust
+ /// # use pin_init::*;
+ /// # use core::{ptr::addr_of_mut, marker::PhantomPinned};
+ /// #[pin_data]
+ /// #[derive(Zeroable)]
+ /// struct Buf {
+ /// // `ptr` points into `buf`.
+ /// ptr: *mut u8,
+ /// buf: [u8; 64],
+ /// #[pin]
+ /// pin: PhantomPinned,
+ /// }
+ ///
+ /// let init = pin_init!(&this in Buf {
+ /// buf: [0; 64],
+ /// // SAFETY: TODO.
+ /// ptr: unsafe { addr_of_mut!((*this.as_ptr()).buf).cast() },
+ /// pin: PhantomPinned,
+ /// });
+ /// let init = pin_init!(Buf {
+ /// buf: [1; 64],
+ /// ..Zeroable::zeroed()
+ /// });
+ /// ```
+ ///
+ /// [`NonNull<Self>`]: core::ptr::NonNull
+ // For a detailed example of how this macro works, see the module documentation of the hidden
+ // module `macros` inside of `macros.rs`.
+ #[macro_export]
+ macro_rules! pin_init {
+ ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
+ $($fields:tt)*
+ }) => {
+ $crate::try_pin_init!($(&$this in)? $t $(::<$($generics),*>)? {
+ $($fields)*
+ }? ::core::convert::Infallible)
+ };
+ }
+
+ /// Construct an in-place, fallible pinned initializer for `struct`s.
+ ///
+ /// If the initialization can complete without error (or [`Infallible`]), then use [`pin_init!`].
+ ///
+ /// You can use the `?` operator or use `return Err(err)` inside the initializer to stop
+ /// initialization and return the error.
+ ///
+ /// IMPORTANT: if you have `unsafe` code inside of the initializer you have to ensure that when
+ /// initialization fails, the memory can be safely deallocated without any further modifications.
+ ///
+ /// The syntax is identical to [`pin_init!`] with the following exception: you must append `? $type`
+ /// after the `struct` initializer to specify the error type you want to use.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/error.rs"] mod error; use error::Error;
+ /// use pin_init::{pin_data, try_pin_init, PinInit, InPlaceInit, zeroed};
+ ///
+ /// #[pin_data]
+ /// struct BigBuf {
+ /// big: Box<[u8; 1024 * 1024 * 1024]>,
+ /// small: [u8; 1024 * 1024],
+ /// ptr: *mut u8,
+ /// }
+ ///
+ /// impl BigBuf {
+ /// fn new() -> impl PinInit<Self, Error> {
+ /// try_pin_init!(Self {
+ /// big: Box::init(zeroed())?,
+ /// small: [0; 1024 * 1024],
+ /// ptr: core::ptr::null_mut(),
+ /// }? Error)
+ /// }
+ /// }
+ /// # let _ = Box::pin_init(BigBuf::new());
+ /// ```
+ // For a detailed example of how this macro works, see the module documentation of the hidden
+ // module `macros` inside of `macros.rs`.
+ #[macro_export]
+ macro_rules! try_pin_init {
+ ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
+ $($fields:tt)*
+ }? $err:ty) => {
+ $crate::__init_internal!(
+ @this($($this)?),
+ @typ($t $(::<$($generics),*>)? ),
+ @fields($($fields)*),
+ @error($err),
+ @data(PinData, use_data),
+ @has_data(HasPinData, __pin_data),
+ @construct_closure(pin_init_from_closure),
+ @munch_fields($($fields)*),
+ )
+ }
+ }
+
+ /// Construct an in-place initializer for `struct`s.
+ ///
+ /// This macro defaults the error to [`Infallible`]. If you need a different error, then use
+ /// [`try_init!`].
+ ///
+ /// The syntax is identical to [`pin_init!`] and its safety caveats also apply:
+ /// - `unsafe` code must guarantee either full initialization or return an error and allow
+ /// deallocation of the memory.
+ /// - the fields are initialized in the order given in the initializer.
+ /// - no references to fields are allowed to be created inside of the initializer.
+ ///
+ /// This initializer is for initializing data in-place that might later be moved. If you want to
+ /// pin-initialize, use [`pin_init!`].
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/error.rs"] mod error; use error::Error;
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # use pin_init::InPlaceInit;
+ /// use pin_init::{init, Init, zeroed};
+ ///
+ /// struct BigBuf {
+ /// small: [u8; 1024 * 1024],
+ /// }
+ ///
+ /// impl BigBuf {
+ /// fn new() -> impl Init<Self> {
+ /// init!(Self {
+ /// small <- zeroed(),
+ /// })
+ /// }
+ /// }
+ /// # let _ = Box::init(BigBuf::new());
+ /// ```
+ // For a detailed example of how this macro works, see the module documentation of the hidden
+ // module `macros` inside of `macros.rs`.
+ #[macro_export]
+ macro_rules! init {
+ ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
+ $($fields:tt)*
+ }) => {
+ $crate::try_init!($(&$this in)? $t $(::<$($generics),*>)? {
+ $($fields)*
+ }? ::core::convert::Infallible)
+ }
+ }
+
+ /// Construct an in-place fallible initializer for `struct`s.
+ ///
+ /// If the initialization can complete without error (or [`Infallible`]), then use
+ /// [`init!`].
+ ///
+ /// The syntax is identical to [`try_pin_init!`]. You need to specify a custom error
+ /// via `? $type` after the `struct` initializer.
+ /// The safety caveats from [`try_pin_init!`] also apply:
+ /// - `unsafe` code must guarantee either full initialization or return an error and allow
+ /// deallocation of the memory.
+ /// - the fields are initialized in the order given in the initializer.
+ /// - no references to fields are allowed to be created inside of the initializer.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![feature(allocator_api)]
+ /// # use core::alloc::AllocError;
+ /// # use pin_init::InPlaceInit;
+ /// use pin_init::{try_init, Init, zeroed};
+ ///
+ /// struct BigBuf {
+ /// big: Box<[u8; 1024 * 1024 * 1024]>,
+ /// small: [u8; 1024 * 1024],
+ /// }
+ ///
+ /// impl BigBuf {
+ /// fn new() -> impl Init<Self, AllocError> {
+ /// try_init!(Self {
+ /// big: Box::init(zeroed())?,
+ /// small: [0; 1024 * 1024],
+ /// }? AllocError)
+ /// }
+ /// }
+ /// # let _ = Box::init(BigBuf::new());
+ /// ```
+ // For a detailed example of how this macro works, see the module documentation of the hidden
+ // module `macros` inside of `macros.rs`.
+ #[macro_export]
+ macro_rules! try_init {
+ ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
+ $($fields:tt)*
+ }? $err:ty) => {
+ $crate::__init_internal!(
+ @this($($this)?),
+ @typ($t $(::<$($generics),*>)?),
+ @fields($($fields)*),
+ @error($err),
+ @data(InitData, /*no use_data*/),
+ @has_data(HasInitData, __init_data),
+ @construct_closure(init_from_closure),
+ @munch_fields($($fields)*),
+ )
+ }
+ }
+
+ /// Asserts that a field on a struct using `#[pin_data]` is marked with `#[pin]` ie. that it is
+ /// structurally pinned.
+ ///
+ /// # Example
+ ///
+ /// This will succeed:
+ /// ```
+ /// use pin_init::{pin_data, assert_pinned};
+ ///
+ /// #[pin_data]
+ /// struct MyStruct {
+ /// #[pin]
+ /// some_field: u64,
+ /// }
+ ///
+ /// assert_pinned!(MyStruct, some_field, u64);
+ /// ```
+ ///
+ /// This will fail:
+ /// ```compile_fail
+ /// use pin_init::{pin_data, assert_pinned};
+ ///
+ /// #[pin_data]
+ /// struct MyStruct {
+ /// some_field: u64,
+ /// }
+ ///
+ /// assert_pinned!(MyStruct, some_field, u64);
+ /// ```
+ ///
+ /// Some uses of the macro may trigger the `can't use generic parameters from outer item` error. To
+ /// work around this, you may pass the `inline` parameter to the macro. The `inline` parameter can
+ /// only be used when the macro is invoked from a function body.
+ /// ```
+ /// # use core::pin::Pin;
+ /// use pin_init::{pin_data, assert_pinned};
+ ///
+ /// #[pin_data]
+ /// struct Foo<T> {
+ /// #[pin]
+ /// elem: T,
+ /// }
+ ///
+ /// impl<T> Foo<T> {
+ /// fn project(self: Pin<&mut Self>) -> Pin<&mut T> {
+ /// assert_pinned!(Foo<T>, elem, T, inline);
+ ///
+ /// // SAFETY: The field is structurally pinned.
+ /// unsafe { self.map_unchecked_mut(|me| &mut me.elem) }
+ /// }
+ /// }
+ /// ```
+ #[macro_export]
+ macro_rules! assert_pinned {
+ ($ty:ty, $field:ident, $field_ty:ty, inline) => {
+ let _ = move |ptr: *mut $field_ty| {
+ // SAFETY: This code is unreachable.
+ let data = unsafe { <$ty as $crate::__internal::HasPinData>::__pin_data() };
+ let init = $crate::__internal::AlwaysFail::<$field_ty>::new();
+ // SAFETY: This code is unreachable.
+ unsafe { data.$field(ptr, init) }.ok();
+ };
+ };
+
+ ($ty:ty, $field:ident, $field_ty:ty) => {
+ const _: () = {
+ $crate::assert_pinned!($ty, $field, $field_ty, inline);
+ };
+ };
+ }
+
+ /// A pin-initializer for the type `T`.
+ ///
+ /// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
+ /// be [`Box<T>`], [`Arc<T>`] or even the stack (see [`stack_pin_init!`]).
+ ///
+ /// Also see the [module description](self).
+ ///
+ /// # Safety
+ ///
+ /// When implementing this trait you will need to take great care. Also there are probably very few
+ /// cases where a manual implementation is necessary. Use [`pin_init_from_closure`] where possible.
+ ///
+ /// The [`PinInit::__pinned_init`] function:
+ /// - returns `Ok(())` if it initialized every field of `slot`,
+ /// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
+ /// - `slot` can be deallocated without UB occurring,
+ /// - `slot` does not need to be dropped,
+ /// - `slot` is not partially initialized.
+ /// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
+ ///
+ #[cfg_attr(
+ kernel,
+ doc = "[`Arc<T>`]: https://rust.docs.kernel.org/kernel/sync/struct.Arc.html"
+ )]
+ #[cfg_attr(
+ kernel,
+ doc = "[`Box<T>`]: https://rust.docs.kernel.org/kernel/alloc/kbox/struct.Box.html"
+ )]
+ #[cfg_attr(not(kernel), doc = "[`Arc<T>`]: alloc::alloc::sync::Arc")]
+ #[cfg_attr(not(kernel), doc = "[`Box<T>`]: alloc::alloc::boxed::Box")]
+ #[must_use = "An initializer must be used in order to create its value."]
+ pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
+ /// Initializes `slot`.
+ ///
+ /// # Safety
+ ///
+ /// - `slot` is a valid pointer to uninitialized memory.
+ /// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
+ /// deallocate.
+ /// - `slot` will not move until it is dropped, i.e. it will be pinned.
+ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E>;
+
+ /// First initializes the value using `self` then calls the function `f` with the initialized
+ /// value.
+ ///
+ /// If `f` returns an error the value is dropped and the initializer will forward the error.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # use pin_init::*;
+ /// let mtx_init = CMutex::new(42);
+ /// // Make the initializer print the value.
+ /// let mtx_init = mtx_init.pin_chain(|mtx| {
+ /// println!("{:?}", mtx.get_data_mut());
+ /// Ok(())
+ /// });
+ /// ```
+ fn pin_chain<F>(self, f: F) -> ChainPinInit<Self, F, T, E>
+ where
+ F: FnOnce(Pin<&mut T>) -> Result<(), E>,
+ {
+ ChainPinInit(self, f, PhantomData)
+ }
+ }
+
+ /// An initializer returned by [`PinInit::pin_chain`].
+ pub struct ChainPinInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, T)>);
+
+ // SAFETY: The `__pinned_init` function is implemented such that it
+ // - returns `Ok(())` on successful initialization,
+ // - returns `Err(err)` on error and in this case `slot` will be dropped.
+ // - considers `slot` pinned.
+ unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainPinInit<I, F, T, E>
+ where
+ I: PinInit<T, E>,
+ F: FnOnce(Pin<&mut T>) -> Result<(), E>,
+ {
+ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
+ // SAFETY: All requirements fulfilled since this function is `__pinned_init`.
+ unsafe { self.0.__pinned_init(slot)? };
+ // SAFETY: The above call initialized `slot` and we still have unique access.
+ let val = unsafe { &mut *slot };
+ // SAFETY: `slot` is considered pinned.
+ let val = unsafe { Pin::new_unchecked(val) };
+ // SAFETY: `slot` was initialized above.
+ (self.1)(val).inspect_err(|_| unsafe { core::ptr::drop_in_place(slot) })
+ }
+ }
+
+ /// An initializer for `T`.
+ ///
+ /// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
+ /// be [`Box<T>`], [`Arc<T>`] or even the stack (see [`stack_pin_init!`]). Because
+ /// [`PinInit<T, E>`] is a super trait, you can use every function that takes it as well.
+ ///
+ /// Also see the [module description](self).
+ ///
+ /// # Safety
+ ///
+ /// When implementing this trait you will need to take great care. Also there are probably very few
+ /// cases where a manual implementation is necessary. Use [`init_from_closure`] where possible.
+ ///
+ /// The [`Init::__init`] function:
+ /// - returns `Ok(())` if it initialized every field of `slot`,
+ /// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
+ /// - `slot` can be deallocated without UB occurring,
+ /// - `slot` does not need to be dropped,
+ /// - `slot` is not partially initialized.
+ /// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
+ ///
+ /// The `__pinned_init` function from the supertrait [`PinInit`] needs to execute the exact same
+ /// code as `__init`.
+ ///
+ /// Contrary to its supertype [`PinInit<T, E>`] the caller is allowed to
+ /// move the pointee after initialization.
+ ///
+ #[cfg_attr(
+ kernel,
+ doc = "[`Arc<T>`]: https://rust.docs.kernel.org/kernel/sync/struct.Arc.html"
+ )]
+ #[cfg_attr(
+ kernel,
+ doc = "[`Box<T>`]: https://rust.docs.kernel.org/kernel/alloc/kbox/struct.Box.html"
+ )]
+ #[cfg_attr(not(kernel), doc = "[`Arc<T>`]: alloc::alloc::sync::Arc")]
+ #[cfg_attr(not(kernel), doc = "[`Box<T>`]: alloc::alloc::boxed::Box")]
+ #[must_use = "An initializer must be used in order to create its value."]
+ pub unsafe trait Init<T: ?Sized, E = Infallible>: PinInit<T, E> {
+ /// Initializes `slot`.
+ ///
+ /// # Safety
+ ///
+ /// - `slot` is a valid pointer to uninitialized memory.
+ /// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
+ /// deallocate.
+ unsafe fn __init(self, slot: *mut T) -> Result<(), E>;
+
+ /// First initializes the value using `self` then calls the function `f` with the initialized
+ /// value.
+ ///
+ /// If `f` returns an error the value is dropped and the initializer will forward the error.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![expect(clippy::disallowed_names)]
+ /// use pin_init::{init, zeroed, Init};
+ ///
+ /// struct Foo {
+ /// buf: [u8; 1_000_000],
+ /// }
+ ///
+ /// impl Foo {
+ /// fn setup(&mut self) {
+ /// println!("Setting up foo");
+ /// }
+ /// }
+ ///
+ /// let foo = init!(Foo {
+ /// buf <- zeroed()
+ /// }).chain(|foo| {
+ /// foo.setup();
+ /// Ok(())
+ /// });
+ /// ```
+ fn chain<F>(self, f: F) -> ChainInit<Self, F, T, E>
+ where
+ F: FnOnce(&mut T) -> Result<(), E>,
+ {
+ ChainInit(self, f, PhantomData)
+ }
+ }
+
+ /// An initializer returned by [`Init::chain`].
+ pub struct ChainInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, T)>);
+
+ // SAFETY: The `__init` function is implemented such that it
+ // - returns `Ok(())` on successful initialization,
+ // - returns `Err(err)` on error and in this case `slot` will be dropped.
+ unsafe impl<T: ?Sized, E, I, F> Init<T, E> for ChainInit<I, F, T, E>
+ where
+ I: Init<T, E>,
+ F: FnOnce(&mut T) -> Result<(), E>,
+ {
+ unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
+ // SAFETY: All requirements fulfilled since this function is `__init`.
+ unsafe { self.0.__pinned_init(slot)? };
+ // SAFETY: The above call initialized `slot` and we still have unique access.
+ (self.1)(unsafe { &mut *slot }).inspect_err(|_|
+ // SAFETY: `slot` was initialized above.
+ unsafe { core::ptr::drop_in_place(slot) })
+ }
+ }
+
+ // SAFETY: `__pinned_init` behaves exactly the same as `__init`.
+ unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainInit<I, F, T, E>
+ where
+ I: Init<T, E>,
+ F: FnOnce(&mut T) -> Result<(), E>,
+ {
+ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
+ // SAFETY: `__init` has less strict requirements compared to `__pinned_init`.
+ unsafe { self.__init(slot) }
+ }
+ }
+
+ /// Creates a new [`PinInit<T, E>`] from the given closure.
+ ///
+ /// # Safety
+ ///
+ /// The closure:
+ /// - returns `Ok(())` if it initialized every field of `slot`,
+ /// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
+ /// - `slot` can be deallocated without UB occurring,
+ /// - `slot` does not need to be dropped,
+ /// - `slot` is not partially initialized.
+ /// - may assume that the `slot` does not move if `T: !Unpin`,
+ /// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
+ #[inline]
+ pub const unsafe fn pin_init_from_closure<T: ?Sized, E>(
+ f: impl FnOnce(*mut T) -> Result<(), E>,
+ ) -> impl PinInit<T, E> {
+ __internal::InitClosure(f, PhantomData)
+ }
+
+ /// Creates a new [`Init<T, E>`] from the given closure.
+ ///
+ /// # Safety
+ ///
+ /// The closure:
+ /// - returns `Ok(())` if it initialized every field of `slot`,
+ /// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
+ /// - `slot` can be deallocated without UB occurring,
+ /// - `slot` does not need to be dropped,
+ /// - `slot` is not partially initialized.
+ /// - the `slot` may move after initialization.
+ /// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
+ #[inline]
+ pub const unsafe fn init_from_closure<T: ?Sized, E>(
+ f: impl FnOnce(*mut T) -> Result<(), E>,
+ ) -> impl Init<T, E> {
+ __internal::InitClosure(f, PhantomData)
+ }
+
+ /// An initializer that leaves the memory uninitialized.
+ ///
+ /// The initializer is a no-op. The `slot` memory is not changed.
+ #[inline]
+ pub fn uninit<T, E>() -> impl Init<MaybeUninit<T>, E> {
+ // SAFETY: The memory is allowed to be uninitialized.
+ unsafe { init_from_closure(|_| Ok(())) }
+ }
+
+ /// Initializes an array by initializing each element via the provided initializer.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # use pin_init::*;
+ /// use pin_init::init_array_from_fn;
+ /// let array: Box<[usize; 1_000]> = Box::init(init_array_from_fn(|i| i)).unwrap();
+ /// assert_eq!(array.len(), 1_000);
+ /// ```
+ pub fn init_array_from_fn<I, const N: usize, T, E>(
+ mut make_init: impl FnMut(usize) -> I,
+ ) -> impl Init<[T; N], E>
+ where
+ I: Init<T, E>,
+ {
+ let init = move |slot: *mut [T; N]| {
+ let slot = slot.cast::<T>();
+ for i in 0..N {
+ let init = make_init(i);
+ // SAFETY: Since 0 <= `i` < N, it is still in bounds of `[T; N]`.
+ let ptr = unsafe { slot.add(i) };
+ // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
+ // requirements.
+ if let Err(e) = unsafe { init.__init(ptr) } {
+ // SAFETY: The loop has initialized the elements `slot[0..i]` and since we return
+ // `Err` below, `slot` will be considered uninitialized memory.
+ unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
+ return Err(e);
+ }
+ }
+ Ok(())
+ };
+ // SAFETY: The initializer above initializes every element of the array. On failure it drops
+ // any initialized elements and returns `Err`.
+ unsafe { init_from_closure(init) }
+ }
+
+ /// Initializes an array by initializing each element via the provided initializer.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # use pin_init::*;
+ /// # use core::pin::Pin;
+ /// use pin_init::pin_init_array_from_fn;
+ /// use std::sync::Arc;
+ /// let array: Pin<Arc<[CMutex<usize>; 1_000]>> =
+ /// Arc::pin_init(pin_init_array_from_fn(|i| CMutex::new(i))).unwrap();
+ /// assert_eq!(array.len(), 1_000);
+ /// ```
+ pub fn pin_init_array_from_fn<I, const N: usize, T, E>(
+ mut make_init: impl FnMut(usize) -> I,
+ ) -> impl PinInit<[T; N], E>
+ where
+ I: PinInit<T, E>,
+ {
+ let init = move |slot: *mut [T; N]| {
+ let slot = slot.cast::<T>();
+ for i in 0..N {
+ let init = make_init(i);
+ // SAFETY: Since 0 <= `i` < N, it is still in bounds of `[T; N]`.
+ let ptr = unsafe { slot.add(i) };
+ // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
+ // requirements.
+ if let Err(e) = unsafe { init.__pinned_init(ptr) } {
+ // SAFETY: The loop has initialized the elements `slot[0..i]` and since we return
+ // `Err` below, `slot` will be considered uninitialized memory.
+ unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
+ return Err(e);
+ }
+ }
+ Ok(())
+ };
+ // SAFETY: The initializer above initializes every element of the array. On failure it drops
+ // any initialized elements and returns `Err`.
+ unsafe { pin_init_from_closure(init) }
+ }
+
+ // SAFETY: Every type can be initialized by-value.
+ unsafe impl<T, E> Init<T, E> for T {
+ unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
+ // SAFETY: TODO.
+ unsafe { slot.write(self) };
+ Ok(())
+ }
+ }
+
+ // SAFETY: Every type can be initialized by-value. `__pinned_init` calls `__init`.
+ unsafe impl<T, E> PinInit<T, E> for T {
+ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
+ // SAFETY: TODO.
+ unsafe { self.__init(slot) }
+ }
+ }
+
+ /// Smart pointer containing uninitialized memory and that can write a value.
+ pub trait InPlaceWrite<T> {
+ /// The type `Self` turns into when the contents are initialized.
+ type Initialized;
+
+ /// Use the given initializer to write a value into `self`.
+ ///
+ /// Does not drop the current value and considers it as uninitialized memory.
+ fn write_init<E>(self, init: impl Init<T, E>) -> Result<Self::Initialized, E>;
+
+ /// Use the given pin-initializer to write a value into `self`.
+ ///
+ /// Does not drop the current value and considers it as uninitialized memory.
+ fn write_pin_init<E>(self, init: impl PinInit<T, E>) -> Result<Pin<Self::Initialized>, E>;
+ }
+
+ /// Trait facilitating pinned destruction.
+ ///
+ /// Use [`pinned_drop`] to implement this trait safely:
+ ///
+ /// ```rust
+ /// # #![feature(allocator_api)]
+ /// # #[path = "../examples/mutex.rs"] mod mutex; use mutex::*;
+ /// # use pin_init::*;
+ /// use core::pin::Pin;
+ /// #[pin_data(PinnedDrop)]
+ /// struct Foo {
+ /// #[pin]
+ /// mtx: CMutex<usize>,
+ /// }
+ ///
+ /// #[pinned_drop]
+ /// impl PinnedDrop for Foo {
+ /// fn drop(self: Pin<&mut Self>) {
+ /// println!("Foo is being dropped!");
+ /// }
+ /// }
+ /// ```
+ ///
+ /// # Safety
+ ///
+ /// This trait must be implemented via the [`pinned_drop`] proc-macro attribute on the impl.
+ pub unsafe trait PinnedDrop: __internal::HasPinData {
+ /// Executes the pinned destructor of this type.
+ ///
+ /// While this function is marked safe, it is actually unsafe to call it manually. For this
+ /// reason it takes an additional parameter. This type can only be constructed by `unsafe` code
+ /// and thus prevents this function from being called where it should not.
+ ///
+ /// This extra parameter will be generated by the `#[pinned_drop]` proc-macro attribute
+ /// automatically.
+ fn drop(self: Pin<&mut Self>, only_call_from_drop: __internal::OnlyCallFromDrop);
+ }
+
+ /// Marker trait for types that can be initialized by writing just zeroes.
+ ///
+ /// # Safety
+ ///
+ /// The bit pattern consisting of only zeroes is a valid bit pattern for this type. In other words,
+ /// this is not UB:
+ ///
+ /// ```rust,ignore
+ /// let val: Self = unsafe { core::mem::zeroed() };
+ /// ```
+ pub unsafe trait Zeroable {}
+
+ /// Marker trait for types that allow `Option<Self>` to be set to all zeroes in order to write
+ /// `None` to that location.
+ ///
+ /// # Safety
+ ///
+ /// The implementer needs to ensure that `unsafe impl Zeroable for Option<Self> {}` is sound.
+ pub unsafe trait ZeroableOption {}
+
+ // SAFETY: by the safety requirement of `ZeroableOption`, this is valid.
+ unsafe impl<T: ZeroableOption> Zeroable for Option<T> {}
+
+ /// Create a new zeroed T.
+ ///
+ /// The returned initializer will write `0x00` to every byte of the given `slot`.
+ #[inline]
+ pub fn zeroed<T: Zeroable>() -> impl Init<T> {
+ // SAFETY: Because `T: Zeroable`, all bytes zero is a valid bit pattern for `T`
+ // and because we write all zeroes, the memory is initialized.
+ unsafe {
+ init_from_closure(|slot: *mut T| {
+ slot.write_bytes(0, 1);
+ Ok(())
+ })
+ }
+ }
+
+ macro_rules! impl_zeroable {
+ ($($({$($generics:tt)*})? $t:ty, )*) => {
+ // SAFETY: Safety comments written in the macro invocation.
+ $(unsafe impl$($($generics)*)? Zeroable for $t {})*
+ };
+ }
+
+ impl_zeroable! {
+ // SAFETY: All primitives that are allowed to be zero.
+ bool,
+ char,
+ u8, u16, u32, u64, u128, usize,
+ i8, i16, i32, i64, i128, isize,
+ f32, f64,
+
+ // Note: do not add uninhabited types (such as `!` or `core::convert::Infallible`) to this list;
+ // creating an instance of an uninhabited type is immediate undefined behavior. For more on
+ // uninhabited/empty types, consult The Rustonomicon:
+ // <https://doc.rust-lang.org/stable/nomicon/exotic-sizes.html#empty-types>. The Rust Reference
+ // also has information on undefined behavior:
+ // <https://doc.rust-lang.org/stable/reference/behavior-considered-undefined.html>.
+ //
+ // SAFETY: These are inhabited ZSTs; there is nothing to zero and a valid value exists.
+ {<T: ?Sized>} PhantomData<T>, core::marker::PhantomPinned, (),
+
+ // SAFETY: Type is allowed to take any value, including all zeros.
+ {<T>} MaybeUninit<T>,
+
+ // SAFETY: `T: Zeroable` and `UnsafeCell` is `repr(transparent)`.
+ {<T: ?Sized + Zeroable>} UnsafeCell<T>,
+
-
- // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).
- //
- // In this case we are allowed to use `T: ?Sized`, since all zeros is the `None` variant.
- {<T: ?Sized>} Option<NonNull<T>>,
++ // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee:
++ // https://doc.rust-lang.org/stable/std/option/index.html#representation).
+ Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>,
+ Option<NonZeroU128>, Option<NonZeroUsize>,
+ Option<NonZeroI8>, Option<NonZeroI16>, Option<NonZeroI32>, Option<NonZeroI64>,
+ Option<NonZeroI128>, Option<NonZeroIsize>,
++ {<T>} Option<NonNull<T>>,
+
+ // SAFETY: `null` pointer is valid.
+ //
+ // We cannot use `T: ?Sized`, since the VTABLE pointer part of fat pointers is not allowed to be
+ // null.
+ //
+ // When `Pointee` gets stabilized, we could use
+ // `T: ?Sized where <T as Pointee>::Metadata: Zeroable`
+ {<T>} *mut T, {<T>} *const T,
+
+ // SAFETY: `null` pointer is valid and the metadata part of these fat pointers is allowed to be
+ // zero.
+ {<T>} *mut [T], {<T>} *const [T], *mut str, *const str,
+
+ // SAFETY: `T` is `Zeroable`.
+ {<const N: usize, T: Zeroable>} [T; N], {<T: Zeroable>} Wrapping<T>,
+ }
+
+ macro_rules! impl_tuple_zeroable {
+ ($(,)?) => {};
+ ($first:ident, $($t:ident),* $(,)?) => {
+ // SAFETY: All elements are zeroable and padding can be zero.
+ unsafe impl<$first: Zeroable, $($t: Zeroable),*> Zeroable for ($first, $($t),*) {}
+ impl_tuple_zeroable!($($t),* ,);
+ }
+ }
+
+ impl_tuple_zeroable!(A, B, C, D, E, F, G, H, I, J);
projects / users / jedix / linux-maple.git / commitdiff