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use core::{
mem::{self, MaybeUninit},
pin::Pin,
};
use crate::{
generics::{Generics, Type},
project::Project,
};
macro_rules! sp {
($this:ident, $ptr:ident, $generics:ty, $tuple:expr $(,)?) => {{
let $this: Pin<&$generics> =
unsafe { Pin::new_unchecked(&*$ptr.cast::<$generics>()) };
#[allow(unused_variables)]
let $this = Pin::get_ref($this);
unsafe { mem::transmute_copy(&$tuple) }
}};
}
macro_rules! sp_mut {
(
$output:ty,
$this:ident,
$ptr:ident,
($($generic:ty),* $(,)?),
$tuple:expr $(,)?
) => {{
let $this: Pin<&mut ($($generic,)*)> =
unsafe { Pin::new_unchecked(&mut *$ptr.cast::<($($generic,)*)>()) };
#[allow(unused_variables)]
let $this = unsafe { Pin::get_unchecked_mut($this) };
let mut output = MaybeUninit::<$output>::uninit();
unsafe {
*output.as_mut_ptr().cast::<($(Pin<&mut $generic>),* ,)>() = $tuple;
output.assume_init()
}
}};
}
/// `Sp` stands for "Structurally Pinned"
///
/// Functionality is exclusively exposed as associated functions to prevent name
/// collisions with [`Pin`] methods.
#[derive(Debug)]
#[repr(transparent)]
pub struct Sp<T>(T);
impl<T> Sp<T> {
/// Create a new structurally-pinned wrapper.
#[inline]
pub const fn new(inner: T) -> Self {
Self(inner)
}
/// Get a pin-projected reference to the inner value.
#[inline]
pub const fn get(this: Pin<&Self>) -> Pin<&T> {
// SAFETY: Value is never moved out of the reference (pointer
// exclusively used for projection).
let this = Pin::get_ref(this);
let inner = &this.0;
// SAFETY: `self.0` is pinned whenever `self` is
unsafe { Pin::new_unchecked(inner) }
}
/// Get a pin-projected mutable reference to the inner value.
#[inline]
pub const fn get_mut(this: Pin<&mut Self>) -> Pin<&mut T> {
// SAFETY: Value is never moved out of the reference (pointer
// exclusively used for projection).
let this = unsafe { Pin::get_unchecked_mut(this) };
let inner = &mut this.0;
// SAFETY: `self.0` is pinned whenever `self` is
unsafe { Pin::new_unchecked(inner) }
}
/// Project all elements (supports tuples with up to 7 elements).
#[inline]
pub const fn project(this: Pin<&Self>) -> T::Projected<'_>
where
T: Project,
Type<T>: Generics,
{
let ptr: *const T = Sp::get(this).get_ref();
match T::TYPE {
Type::Unit(_) => sp!(this, ptr, (), ()),
Type::TupleA => {
sp!(
this,
ptr,
(<Type<T> as Generics>::A,),
(Pin::new_unchecked(&this.0),),
)
}
Type::TupleB => {
sp!(
this,
ptr,
(<Type<T> as Generics>::A, <Type<T> as Generics>::B),
(Pin::new_unchecked(&this.0), Pin::new_unchecked(&this.1)),
)
}
Type::TupleC => {
sp!(
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
),
(
Pin::new_unchecked(&this.0),
Pin::new_unchecked(&this.1),
Pin::new_unchecked(&this.2),
),
)
}
Type::TupleD => {
sp!(
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
<Type<T> as Generics>::D,
),
(
Pin::new_unchecked(&this.0),
Pin::new_unchecked(&this.1),
Pin::new_unchecked(&this.2),
Pin::new_unchecked(&this.3),
),
)
}
Type::TupleE => {
sp!(
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
<Type<T> as Generics>::D,
<Type<T> as Generics>::E,
),
(
Pin::new_unchecked(&this.0),
Pin::new_unchecked(&this.1),
Pin::new_unchecked(&this.2),
Pin::new_unchecked(&this.3),
Pin::new_unchecked(&this.4),
),
)
}
Type::TupleF => {
sp!(
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
<Type<T> as Generics>::D,
<Type<T> as Generics>::E,
<Type<T> as Generics>::F,
),
(
Pin::new_unchecked(&this.0),
Pin::new_unchecked(&this.1),
Pin::new_unchecked(&this.2),
Pin::new_unchecked(&this.3),
Pin::new_unchecked(&this.4),
Pin::new_unchecked(&this.5),
),
)
}
Type::TupleG => {
sp!(
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
<Type<T> as Generics>::D,
<Type<T> as Generics>::E,
<Type<T> as Generics>::F,
<Type<T> as Generics>::G,
),
(
Pin::new_unchecked(&this.0),
Pin::new_unchecked(&this.1),
Pin::new_unchecked(&this.2),
Pin::new_unchecked(&this.3),
Pin::new_unchecked(&this.4),
Pin::new_unchecked(&this.5),
Pin::new_unchecked(&this.6),
),
)
}
}
}
/// Project all elements mutably (supports tuples with up to 7 elements).
#[inline]
pub const fn project_mut(this: Pin<&mut Self>) -> T::ProjectedMut<'_>
where
T: Project,
Type<T>: Generics,
{
let ptr: *mut T = unsafe { Self::get_mut(this).get_unchecked_mut() };
match T::TYPE {
Type::Unit(_) => unsafe { mem::transmute_copy(&()) },
Type::TupleA => {
sp_mut!(
T::ProjectedMut<'_>,
this,
ptr,
(<Type<T> as Generics>::A,),
(Pin::new_unchecked(&mut this.0),),
)
}
Type::TupleB => {
sp_mut!(
T::ProjectedMut<'_>,
this,
ptr,
(<Type<T> as Generics>::A, <Type<T> as Generics>::B),
(
Pin::new_unchecked(&mut this.0),
Pin::new_unchecked(&mut this.1),
),
)
}
Type::TupleC => {
sp_mut!(
T::ProjectedMut<'_>,
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
),
(
Pin::new_unchecked(&mut this.0),
Pin::new_unchecked(&mut this.1),
Pin::new_unchecked(&mut this.2),
),
)
}
Type::TupleD => {
sp_mut!(
T::ProjectedMut<'_>,
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
<Type<T> as Generics>::D,
),
(
Pin::new_unchecked(&mut this.0),
Pin::new_unchecked(&mut this.1),
Pin::new_unchecked(&mut this.2),
Pin::new_unchecked(&mut this.3),
),
)
}
Type::TupleE => {
sp_mut!(
T::ProjectedMut<'_>,
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
<Type<T> as Generics>::D,
<Type<T> as Generics>::E,
),
(
Pin::new_unchecked(&mut this.0),
Pin::new_unchecked(&mut this.1),
Pin::new_unchecked(&mut this.2),
Pin::new_unchecked(&mut this.3),
Pin::new_unchecked(&mut this.4),
),
)
}
Type::TupleF => {
sp_mut!(
T::ProjectedMut<'_>,
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
<Type<T> as Generics>::D,
<Type<T> as Generics>::E,
<Type<T> as Generics>::F,
),
(
Pin::new_unchecked(&mut this.0),
Pin::new_unchecked(&mut this.1),
Pin::new_unchecked(&mut this.2),
Pin::new_unchecked(&mut this.3),
Pin::new_unchecked(&mut this.4),
Pin::new_unchecked(&mut this.5),
),
)
}
Type::TupleG => {
sp_mut!(
T::ProjectedMut<'_>,
this,
ptr,
(
<Type<T> as Generics>::A,
<Type<T> as Generics>::B,
<Type<T> as Generics>::C,
<Type<T> as Generics>::D,
<Type<T> as Generics>::E,
<Type<T> as Generics>::F,
<Type<T> as Generics>::G,
),
(
Pin::new_unchecked(&mut this.0),
Pin::new_unchecked(&mut this.1),
Pin::new_unchecked(&mut this.2),
Pin::new_unchecked(&mut this.3),
Pin::new_unchecked(&mut this.4),
Pin::new_unchecked(&mut this.5),
Pin::new_unchecked(&mut this.6),
),
)
}
}
}
}