--- /dev/null
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#[cfg(all(feature = "alloc", not(feature = "std")))]
+use alloc::{boxed::Box, sync::Arc};
+#[cfg(feature = "alloc")]
+use core::alloc::AllocError;
+use core::{mem::MaybeUninit, pin::Pin};
+#[cfg(feature = "std")]
+use std::sync::Arc;
+
+#[cfg(not(feature = "alloc"))]
+type AllocError = core::convert::Infallible;
+
+use crate::{
+ init_from_closure, pin_init_from_closure, InPlaceWrite, Init, PinInit, ZeroableOption,
+};
+
+pub extern crate alloc;
+
+// 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 and there
+// is no problem with a VTABLE pointer being null.
+unsafe impl<T: ?Sized> ZeroableOption for Box<T> {}
+
+/// Smart pointer that can initialize memory in-place.
+pub trait InPlaceInit<T>: Sized {
+ /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
+ /// type.
+ ///
+ /// If `T: !Unpin` it will not be able to move afterwards.
+ fn try_pin_init<E>(init: impl PinInit<T, E>) -> Result<Pin<Self>, E>
+ where
+ E: From<AllocError>;
+
+ /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
+ /// type.
+ ///
+ /// If `T: !Unpin` it will not be able to move afterwards.
+ fn pin_init(init: impl PinInit<T>) -> Result<Pin<Self>, AllocError> {
+ // SAFETY: We delegate to `init` and only change the error type.
+ let init = unsafe {
+ pin_init_from_closure(|slot| match init.__pinned_init(slot) {
+ Ok(()) => Ok(()),
+ Err(i) => match i {},
+ })
+ };
+ Self::try_pin_init(init)
+ }
+
+ /// Use the given initializer to in-place initialize a `T`.
+ fn try_init<E>(init: impl Init<T, E>) -> Result<Self, E>
+ where
+ E: From<AllocError>;
+
+ /// Use the given initializer to in-place initialize a `T`.
+ fn init(init: impl Init<T>) -> Result<Self, AllocError> {
+ // SAFETY: We delegate to `init` and only change the error type.
+ let init = unsafe {
+ init_from_closure(|slot| match init.__init(slot) {
+ Ok(()) => Ok(()),
+ Err(i) => match i {},
+ })
+ };
+ Self::try_init(init)
+ }
+}
+
+#[cfg(feature = "alloc")]
+macro_rules! try_new_uninit {
+ ($type:ident) => {
+ $type::try_new_uninit()?
+ };
+}
+#[cfg(all(feature = "std", not(feature = "alloc")))]
+macro_rules! try_new_uninit {
+ ($type:ident) => {
+ $type::new_uninit()
+ };
+}
+
+impl<T> InPlaceInit<T> for Box<T> {
+ #[inline]
+ fn try_pin_init<E>(init: impl PinInit<T, E>) -> Result<Pin<Self>, E>
+ where
+ E: From<AllocError>,
+ {
+ try_new_uninit!(Box).write_pin_init(init)
+ }
+
+ #[inline]
+ fn try_init<E>(init: impl Init<T, E>) -> Result<Self, E>
+ where
+ E: From<AllocError>,
+ {
+ try_new_uninit!(Box).write_init(init)
+ }
+}
+
+impl<T> InPlaceInit<T> for Arc<T> {
+ #[inline]
+ fn try_pin_init<E>(init: impl PinInit<T, E>) -> Result<Pin<Self>, E>
+ where
+ E: From<AllocError>,
+ {
+ let mut this = try_new_uninit!(Arc);
+ let Some(slot) = Arc::get_mut(&mut this) else {
+ // SAFETY: the Arc has just been created and has no external references
+ unsafe { core::hint::unreachable_unchecked() }
+ };
+ let slot = slot.as_mut_ptr();
+ // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+ // slot is valid and will not be moved, because we pin it later.
+ unsafe { init.__pinned_init(slot)? };
+ // SAFETY: All fields have been initialized and this is the only `Arc` to that data.
+ Ok(unsafe { Pin::new_unchecked(this.assume_init()) })
+ }
+
+ #[inline]
+ fn try_init<E>(init: impl Init<T, E>) -> Result<Self, E>
+ where
+ E: From<AllocError>,
+ {
+ let mut this = try_new_uninit!(Arc);
+ let Some(slot) = Arc::get_mut(&mut this) else {
+ // SAFETY: the Arc has just been created and has no external references
+ unsafe { core::hint::unreachable_unchecked() }
+ };
+ let slot = slot.as_mut_ptr();
+ // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+ // slot is valid.
+ unsafe { init.__init(slot)? };
+ // SAFETY: All fields have been initialized.
+ Ok(unsafe { this.assume_init() })
+ }
+}
+
+impl<T> InPlaceWrite<T> for Box<MaybeUninit<T>> {
+ type Initialized = Box<T>;
+
+ fn write_init<E>(mut self, init: impl Init<T, E>) -> Result<Self::Initialized, E> {
+ let slot = self.as_mut_ptr();
+ // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+ // slot is valid.
+ unsafe { init.__init(slot)? };
+ // SAFETY: All fields have been initialized.
+ Ok(unsafe { self.assume_init() })
+ }
+
+ fn write_pin_init<E>(mut self, init: impl PinInit<T, E>) -> Result<Pin<Self::Initialized>, E> {
+ let slot = self.as_mut_ptr();
+ // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+ // slot is valid and will not be moved, because we pin it later.
+ unsafe { init.__pinned_init(slot)? };
+ // SAFETY: All fields have been initialized.
+ Ok(unsafe { self.assume_init() }.into())
+ }
+}
//! [structurally pinned fields]:
//! https://doc.rust-lang.org/std/pin/index.html#pinning-is-structural-for-field
//! [stack]: crate::stack_pin_init
-//! [`Arc<T>`]: https://rust.docs.kernel.org/kernel/sync/struct.Arc.html
-//! [`Box<T>`]: https://rust.docs.kernel.org/kernel/alloc/kbox/struct.Box.html
+#![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>`]: PinInit
//! [`impl PinInit<T, E>`]: PinInit
//! [`impl Init<T, E>`]: Init
#[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
/// - `slot` is not partially initialized.
/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
///
-/// [`Arc<T>`]: https://rust.docs.kernel.org/kernel/sync/struct.Arc.html
-/// [`Box<T>`]: https://rust.docs.kernel.org/kernel/alloc/kbox/struct.Box.html
+#[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`.
/// Contrary to its supertype [`PinInit<T, E>`] the caller is allowed to
/// move the pointee after initialization.
///
-/// [`Arc<T>`]: https://rust.docs.kernel.org/kernel/sync/struct.Arc.html
-/// [`Box<T>`]: https://rust.docs.kernel.org/kernel/alloc/kbox/struct.Box.html
+#[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`.
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