1 files changed, 170 insertions, 0 deletions
diff --git a/src/lockable.rs b/src/lockable.rs
new file mode 100644
index 0000000..9b754a3
--- /dev/null
+++ b/src/lockable.rs
@@ -0,0 +1,170 @@
+use std::mem::MaybeUninit;
+
+use crate::mutex::{Mutex, MutexRef, RawMutex};
+
+mod sealed {
+	#[allow(clippy::wildcard_imports)]
+	use super::*;
+	pub trait Sealed {}
+	impl<'a, T, R: RawMutex + 'a> Sealed for Mutex<T, R> {}
+	impl<T: Sealed> Sealed for &T {}
+	impl<T: Sealed> Sealed for &mut T {}
+	impl<'a, A: Lockable<'a>, B: Lockable<'a>> Sealed for (A, B) {}
+	impl<'a, T: Lockable<'a>, const N: usize> Sealed for [T; N] {}
+}
+
+/// A type that may be locked and unlocked
+///
+/// # Safety
+///
+/// A deadlock must never occur. The `unlock` method must correctly unlock the
+/// data.
+pub unsafe trait Lockable<'a>: sealed::Sealed {
+	/// The output of the lock
+	type Output;
+
+	/// Blocks until the lock is acquired
+	///
+	/// # Safety
+	///
+	/// It is undefined behavior to:
+	/// * Use this without ownership of the [`ThreadKey`], which should last as
+	/// long as the return value is alive.
+	/// * Call this on multiple locks without unlocking first.
+	unsafe fn lock(&'a self) -> Self::Output;
+
+	/// Attempt to lock without blocking.
+	///
+	/// Returns `Ok` if successful, `None` otherwise.
+	///
+	/// # Safety
+	///
+	/// It is undefined behavior to use this without ownership of the
+	/// [`ThreadKey`], which should last as long as the return value is alive.
+	unsafe fn try_lock(&'a self) -> Option<Self::Output>;
+
+	/// Release the lock
+	fn unlock(guard: Self::Output);
+}
+
+unsafe impl<'a, T: Lockable<'a>> Lockable<'a> for &T {
+	type Output = T::Output;
+
+	unsafe fn lock(&'a self) -> Self::Output {
+		(*self).lock()
+	}
+
+	unsafe fn try_lock(&'a self) -> Option<Self::Output> {
+		(*self).try_lock()
+	}
+
+	#[allow(clippy::semicolon_if_nothing_returned)]
+	fn unlock(guard: Self::Output) {
+		T::unlock(guard)
+	}
+}
+
+unsafe impl<'a, T: Lockable<'a>> Lockable<'a> for &mut T {
+	type Output = T::Output;
+
+	unsafe fn lock(&'a self) -> Self::Output {
+		(**self).lock()
+	}
+
+	unsafe fn try_lock(&'a self) -> Option<Self::Output> {
+		(**self).try_lock()
+	}
+
+	#[allow(clippy::semicolon_if_nothing_returned)]
+	fn unlock(guard: Self::Output) {
+		T::unlock(guard)
+	}
+}
+
+unsafe impl<'a, T: 'a, R: RawMutex + 'a> Lockable<'a> for Mutex<T, R> {
+	type Output = MutexRef<'a, T, R>;
+
+	unsafe fn lock(&'a self) -> Self::Output {
+		self.lock_ref()
+	}
+
+	unsafe fn try_lock(&'a self) -> Option<Self::Output> {
+		self.try_lock_ref()
+	}
+
+	fn unlock(guard: Self::Output) {
+		drop(guard);
+	}
+}
+
+unsafe impl<'a, A: Lockable<'a>, B: Lockable<'a>> Lockable<'a> for (A, B) {
+	type Output = (A::Output, B::Output);
+
+	unsafe fn lock(&'a self) -> Self::Output {
+		loop {
+			let lock1 = self.0.lock();
+			match self.1.try_lock() {
+				Some(lock2) => return (lock1, lock2),
+				None => A::unlock(lock1),
+			}
+		}
+	}
+
+	unsafe fn try_lock(&'a self) -> Option<Self::Output> {
+		self.0.try_lock().and_then(|guard1| {
+			if let Some(guard2) = self.1.try_lock() {
+				Some((guard1, guard2))
+			} else {
+				A::unlock(guard1);
+				None
+			}
+		})
+	}
+
+	fn unlock(guard: Self::Output) {
+		A::unlock(guard.0);
+		B::unlock(guard.1);
+	}
+}
+
+unsafe impl<'a, T: Lockable<'a>, const N: usize> Lockable<'a> for [T; N] {
+	type Output = [T::Output; N];
+
+	unsafe fn lock(&'a self) -> Self::Output {
+		loop {
+			if let Some(guard) = self.try_lock() {
+				return guard;
+			}
+		}
+	}
+
+	unsafe fn try_lock(&'a self) -> Option<Self::Output> {
+		unsafe fn unlock_partial<'a, T: Lockable<'a>, const N: usize>(
+			guards: [MaybeUninit<T::Output>; N],
+			upto: usize,
+		) {
+			for (i, guard) in guards.into_iter().enumerate() {
+				if i == upto {
+					break;
+				}
+				T::unlock(guard.assume_init());
+			}
+		}
+
+		let mut outputs = MaybeUninit::<[MaybeUninit<T::Output>; N]>::uninit().assume_init();
+		for i in 0..N {
+			if let Some(guard) = self[i].try_lock() {
+				outputs[i].write(guard)
+			} else {
+				unlock_partial::<T, N>(outputs, i);
+				return None;
+			};
+		}
+
+		Some(outputs.map(|mu| mu.assume_init()))
+	}
+
+	fn unlock(guard: Self::Output) {
+		guard.map(T::unlock);
+	}
+}