First commitHEADmain

5 files changed, 261 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
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+++ b/.gitignore
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+/target
diff --git a/Cargo.lock b/Cargo.lock
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+++ b/Cargo.lock
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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "superpin"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
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+++ b/Cargo.toml
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+[package]
+name = "superpin"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/rustfmt.toml b/rustfmt.toml
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+++ b/rustfmt.toml
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+edition = "2021"
+hard_tabs = true
+newline_style = "Unix"
diff --git a/src/lib.rs b/src/lib.rs
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+++ b/src/lib.rs
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+#![no_std]
+
+extern crate alloc;
+
+use alloc::boxed::Box;
+use alloc::rc::Rc;
+use alloc::sync::Arc;
+use core::cmp;
+use core::fmt::{self, Debug, Display, Pointer};
+use core::hash::{Hash, Hasher};
+use core::ops::{Deref, DerefMut};
+
+#[derive(Clone, Copy)]
+#[repr(transparent)]
+pub struct SuperPin<Ptr> {
+	pointer: Ptr,
+}
+
+#[macro_export]
+macro_rules! superpin {
+	($value: expr $(,)?) => {
+		$crate::SuperPin<&mut _> { pointer: &mut { $value } }
+	};
+}
+
+impl<Ptr: Debug> Debug for SuperPin<Ptr> {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		fmt::Debug::fmt(&self.pointer, f)
+	}
+}
+
+impl<Ptr: Display> Display for SuperPin<Ptr> {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		fmt::Display::fmt(&self.pointer, f)
+	}
+}
+
+impl<Ptr: Pointer> Pointer for SuperPin<Ptr> {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		fmt::Pointer::fmt(&self.pointer, f)
+	}
+}
+
+impl<Ptr: Deref, Q: Deref> PartialEq<SuperPin<Q>> for SuperPin<Ptr>
+where
+	Ptr::Target: PartialEq<Q::Target>,
+{
+	fn eq(&self, other: &SuperPin<Q>) -> bool {
+		Ptr::Target::eq(self, other)
+	}
+
+	#[allow(clippy::partialeq_ne_impl)] // We need to copy what the Ptr type does
+	fn ne(&self, other: &SuperPin<Q>) -> bool {
+		Ptr::Target::ne(self, other)
+	}
+}
+
+impl<Ptr: Deref<Target: Eq>> Eq for SuperPin<Ptr> {}
+
+impl<Ptr: Deref, Q: Deref> PartialOrd<SuperPin<Q>> for SuperPin<Ptr>
+where
+	Ptr::Target: PartialOrd<Q::Target>,
+{
+	fn partial_cmp(&self, other: &SuperPin<Q>) -> Option<cmp::Ordering> {
+		Ptr::Target::partial_cmp(self, other)
+	}
+
+	fn lt(&self, other: &SuperPin<Q>) -> bool {
+		Ptr::Target::lt(self, other)
+	}
+
+	fn le(&self, other: &SuperPin<Q>) -> bool {
+		Ptr::Target::le(self, other)
+	}
+
+	fn gt(&self, other: &SuperPin<Q>) -> bool {
+		Ptr::Target::gt(self, other)
+	}
+
+	fn ge(&self, other: &SuperPin<Q>) -> bool {
+		Ptr::Target::ge(self, other)
+	}
+}
+
+impl<Ptr: Deref<Target: Ord>> Ord for SuperPin<Ptr> {
+	fn cmp(&self, other: &Self) -> cmp::Ordering {
+		Ptr::Target::cmp(self, other)
+	}
+}
+
+impl<Ptr: Deref> Hash for SuperPin<Ptr>
+where
+	<Ptr as Deref>::Target: Hash,
+{
+	fn hash<H: Hasher>(&self, state: &mut H) {
+		self.pointer.hash(state);
+	}
+}
+
+impl<Ptr: Deref> Deref for SuperPin<Ptr> {
+	type Target = Ptr::Target;
+
+	fn deref(&self) -> &Self::Target {
+		&self.pointer
+	}
+}
+
+impl<Ptr: DerefMut> DerefMut for SuperPin<Ptr> {
+	fn deref_mut(&mut self) -> &mut Self::Target {
+		&mut self.pointer
+	}
+}
+
+impl<T: ?Sized> From<Box<T>> for SuperPin<Box<T>> {
+	fn from(value: Box<T>) -> Self {
+		// safety: It's not possible to move or replace the insides of a
+		//         SuperPin<Box<T>>, so it's safe to pin it directly without
+		//         any additional requirements.
+		unsafe { Self::new_unchecked(value) }
+	}
+}
+
+impl<Ptr> SuperPin<Ptr> {
+	pub fn boxed<T>(x: T) -> SuperPin<Box<T>> {
+		SuperPin::from(Box::new(x))
+	}
+
+	pub fn rc<T>(value: T) -> SuperPin<Rc<T>> {
+		// safety: It's not possible to move anything behind an Rc
+		unsafe { SuperPin::new_unchecked(Rc::new(value)) }
+	}
+
+	pub fn arc<T>(value: T) -> SuperPin<Arc<T>> {
+		// safety: It's not possible to move anything behind an Arc
+		unsafe { SuperPin::new_unchecked(Arc::new(value)) }
+	}
+}
+
+impl<Ptr: Deref> SuperPin<Ptr> {
+	pub unsafe fn new_unchecked(pointer: Ptr) -> Self {
+		Self { pointer }
+	}
+
+	pub fn as_ref(&self) -> SuperPin<&<Ptr as Deref>::Target> {
+		// safety: the pointee cannot move while it is pinned
+		unsafe { SuperPin::new_unchecked(self.pointer.deref()) }
+	}
+
+	pub unsafe fn into_inner_unchecked(pin: SuperPin<Ptr>) -> Ptr {
+		// safety: the caller must ensure that the value is not moved
+		pin.pointer
+	}
+}
+
+impl<Ptr: DerefMut> SuperPin<Ptr> {
+	pub fn as_mut(&mut self) -> SuperPin<&mut <Ptr as Deref>::Target> {
+		// safety: the pointee cannot move while it is pinned
+		unsafe { SuperPin::new_unchecked(self.pointer.deref_mut()) }
+	}
+
+	pub fn set(&mut self, value: <Ptr as Deref>::Target)
+	where
+		<Ptr as Deref>::Target: Sized,
+	{
+		// safety: the destructor is run and a new valid value of the same type is
+		//         put in its place, so no pinning invariant is violated
+		*self.pointer.deref_mut() = value;
+	}
+}
+
+impl<'a, T: ?Sized> SuperPin<&'a T> {
+	pub unsafe fn map_unchecked<U: ?Sized>(self, func: impl FnOnce(&T) -> &U) -> SuperPin<&'a U> {
+		let new_pointer = func(self.pointer);
+
+		// safety: the caller is responsible for upholding the invariants of
+		//         SuperPin::new_unchecked
+		unsafe { SuperPin::new_unchecked(new_pointer) }
+	}
+
+	pub fn get_ref(self) -> &'a T {
+		// safety: it is impossible to move out of a shared pointer
+		self.pointer
+	}
+}
+
+impl<'a, T: ?Sized> SuperPin<&'a mut T> {
+	pub fn into_ref(self) -> SuperPin<&'a T> {
+		// safety: it is impossible to move out of a shared pointer
+		unsafe { SuperPin::new_unchecked(&*self.pointer) }
+	}
+
+	pub unsafe fn get_unchecked_mut(self) -> &'a mut T {
+		// safety: the caller must ensure the value is not moved out of the pointer
+		self.pointer
+	}
+
+	pub unsafe fn map_unchecked_mut<U: ?Sized>(
+		self,
+		func: impl FnOnce(&mut T) -> &mut U,
+	) -> SuperPin<&'a mut U> {
+		let pointer = &mut *self.pointer;
+		let new_pointer = func(pointer);
+
+		// safety: the caller must uphold the invariants of SuperPin::new_unchecked
+		unsafe { SuperPin::new_unchecked(new_pointer) }
+	}
+}
+
+impl<T: ?Sized> SuperPin<&'static T> {
+	pub fn static_ref(r: &'static T) -> Self {
+		// safety: T is borrowed for the 'static lifetime, which never ends
+		unsafe { SuperPin::new_unchecked(r) }
+	}
+}
+
+impl<T: ?Sized> SuperPin<&'static mut T> {
+	pub fn static_mut(r: &'static mut T) -> Self {
+		// safety: T is borrowed for the 'static lifetime, which never ends
+		unsafe { SuperPin::new_unchecked(r) }
+	}
+}
+
+impl<'a, T> SuperPin<&'a Option<T>> {
+	pub fn as_option_ref(self) -> Option<SuperPin<&'a T>> {
+		unsafe {
+			SuperPin::get_ref(self)
+				.as_ref()
+				// safety: x has to be pinned, because it comes from self
+				.map(|x| SuperPin::new_unchecked(x))
+		}
+	}
+}
+
+impl<'a, T> SuperPin<&'a mut Option<T>> {
+	pub fn as_option_mut(self) -> Option<SuperPin<&'a mut T>> {
+		unsafe {
+			// safety: the value is never moved
+			SuperPin::get_unchecked_mut(self)
+				.as_mut()
+				// safety: x has to be pinned, because it comes from self
+				.map(|x| SuperPin::new_unchecked(x))
+		}
+	}
+}