Refactor Ownership and WeakId into their own files

Author: madsmtm

objc2/src/rc/id.rs

@@ -1,43 +1,16 @@
 use alloc::borrow;
-use alloc::boxed::Box;
-use core::cell::UnsafeCell;
 use core::fmt;
 use core::hash;
 use core::iter::FusedIterator;
 use core::marker::PhantomData;
 use core::mem::ManuallyDrop;
 use core::ops::{Deref, DerefMut};
-use core::ptr;
 use core::ptr::NonNull;
 
 use super::AutoreleasePool;
+use super::{Owned, Ownership, Shared};
 use crate::Message;
 
-/// A type used to mark that a struct owns the object(s) it contains,
-/// so it has the sole references to them.
-pub enum Owned {}
-
-/// A type used to mark that the object(s) a struct contains are shared,
-/// so there may be other references to them.
-pub enum Shared {}
-
-mod private {
-    pub trait Sealed {}
-
-    impl Sealed for super::Owned {}
-    impl Sealed for super::Shared {}
-}
-
-/// A type that marks what type of ownership a struct has over the object(s)
-/// it contains; specifically, either [`Owned`] or [`Shared`].
-///
-/// This trait is sealed and not meant to be implemented outside of the this
-/// crate.
-pub trait Ownership: private::Sealed + 'static {}
-
-impl Ownership for Owned {}
-impl Ownership for Shared {}
-
 /// An pointer for Objective-C reference counted objects.
 ///
 /// [`Id`] strongly references or "retains" the given object `T`, and
@@ -539,148 +512,18 @@ impl<T, O: Ownership> Unpin for Id<T, O> {}
 /// A convenient alias for a shared [`Id`].
 pub type ShareId<T> = Id<T, Shared>;
 
-/// A pointer type for a weak reference to an Objective-C reference counted
-/// object.
-///
-/// Allows breaking reference cycles and safely checking whether the object
-/// has been deallocated.
-#[repr(transparent)]
-pub struct WeakId<T> {
-    /// We give the runtime the address to this box, so that it can modify it
-    /// even if the `WeakId` is moved.
-    ///
-    /// Loading may modify the pointer through a shared reference, so we use
-    /// an UnsafeCell to get a *mut without self being mutable.
-    inner: Box<UnsafeCell<*mut T>>,
-    /// TODO: Variance and dropck
-    item: PhantomData<T>,
-}
-
-impl<T: Message> WeakId<T> {
-    /// Construct a new [`WeakId`] referencing the given shared [`Id`].
-    #[doc(alias = "objc_initWeak")]
-    pub fn new(obj: &Id<T, Shared>) -> Self {
-        // Note that taking `&Id<T, Owned>` would not be safe since that would
-        // allow loading an `Id<T, Shared>` later on.
-
-        // SAFETY: `obj` is valid
-        unsafe { Self::new_inner(&**obj as *const T as *mut T) }
-    }
-
-    /// # Safety
-    ///
-    /// The object must be valid or null.
-    unsafe fn new_inner(obj: *mut T) -> Self {
-        let inner = Box::new(UnsafeCell::new(ptr::null_mut()));
-        // SAFETY: `ptr` will never move, and the caller verifies `obj`
-        objc2_sys::objc_initWeak(inner.get() as _, obj as _);
-        Self {
-            inner,
-            item: PhantomData,
-        }
-    }
-
-    /// Load a shared (and retained) [`Id`] if the object still exists.
-    ///
-    /// Returns [`None`] if the object has been deallocated.
-    #[doc(alias = "upgrade")]
-    #[doc(alias = "objc_loadWeak")]
-    #[doc(alias = "objc_loadWeakRetained")]
-    #[inline]
-    pub fn load(&self) -> Option<Id<T, Shared>> {
-        let ptr: *mut *mut objc2_sys::objc_object = self.inner.get() as _;
-        let obj = unsafe { objc2_sys::objc_loadWeakRetained(ptr) } as *mut T;
-        NonNull::new(obj).map(|obj| unsafe { Id::new(obj) })
-    }
-}
-
-impl<T> Drop for WeakId<T> {
-    /// Drops the `WeakId` pointer.
-    #[doc(alias = "objc_destroyWeak")]
-    fn drop(&mut self) {
-        unsafe {
-            objc2_sys::objc_destroyWeak(self.inner.get() as _);
-        }
-    }
-}
-
-impl<T> Clone for WeakId<T> {
-    /// Makes a clone of the `WeakId` that points to the same object.
-    #[doc(alias = "objc_copyWeak")]
-    fn clone(&self) -> Self {
-        let ptr = Box::new(UnsafeCell::new(ptr::null_mut()));
-        unsafe {
-            objc2_sys::objc_copyWeak(ptr.get() as _, self.inner.get() as _);
-        }
-        Self {
-            inner: ptr,
-            item: PhantomData,
-        }
-    }
-}
-
-impl<T: Message> Default for WeakId<T> {
-    /// Constructs a new `WeakId<T>` that doesn't reference any object.
-    ///
-    /// Calling [`Self::load`] on the return value always gives [`None`].
-    fn default() -> Self {
-        // SAFETY: The pointer is null
-        unsafe { Self::new_inner(ptr::null_mut()) }
-    }
-}
-
-/// This implementation follows the same reasoning as `Id<T, Shared>`.
-unsafe impl<T: Sync + Send> Sync for WeakId<T> {}
-
-/// This implementation follows the same reasoning as `Id<T, Shared>`.
-unsafe impl<T: Sync + Send> Send for WeakId<T> {}
-
-// Unsure about the Debug bound on T, see std::sync::Weak
-impl<T: fmt::Debug> fmt::Debug for WeakId<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "(WeakId)")
-    }
-}
-
-// Underneath this is just a `Box`
-impl<T> Unpin for WeakId<T> {}
-
 #[cfg(test)]
 mod tests {
-    use core::mem::size_of;
     use core::ptr::NonNull;
 
-    use super::{Id, Owned, ShareId, Shared, WeakId};
+    use super::{Id, Shared};
     use crate::runtime::Object;
     use crate::{class, msg_send};
 
     fn retain_count(obj: &Object) -> usize {
         unsafe { msg_send![obj, retainCount] }
     }
 
-    pub struct TestType {
-        _data: [u8; 0], // TODO: `UnsafeCell`?
-    }
-
-    #[test]
-    fn test_size_of() {
-        assert_eq!(size_of::<Id<TestType, Owned>>(), size_of::<&TestType>());
-        assert_eq!(size_of::<Id<TestType, Shared>>(), size_of::<&TestType>());
-        assert_eq!(
-            size_of::<Option<Id<TestType, Owned>>>(),
-            size_of::<&TestType>()
-        );
-        assert_eq!(
-            size_of::<Option<Id<TestType, Shared>>>(),
-            size_of::<&TestType>()
-        );
-
-        assert_eq!(
-            size_of::<Option<WeakId<TestType>>>(),
-            size_of::<*const ()>()
-        );
-    }
-
     #[test]
     fn test_clone() {
         let cls = class!(NSObject);
@@ -701,31 +544,4 @@ mod tests {
         drop(obj);
         assert!(retain_count(&cloned) == 1);
     }
-
-    #[test]
-    fn test_weak() {
-        let cls = class!(NSObject);
-        let obj: ShareId<Object> = unsafe {
-            let obj: *mut Object = msg_send![cls, alloc];
-            let obj: *mut Object = msg_send![obj, init];
-            Id::new(NonNull::new_unchecked(obj))
-        };
-
-        let weak = WeakId::new(&obj);
-        let strong = weak.load().unwrap();
-        let strong_ptr: *const Object = &*strong;
-        let obj_ptr: *const Object = &*obj;
-        assert!(strong_ptr == obj_ptr);
-        drop(strong);
-
-        drop(obj);
-        assert!(weak.load().is_none());
-    }
-
-    #[test]
-    fn test_weak_default() {
-        let weak: WeakId<Object> = WeakId::default();
-        assert!(weak.load().is_none());
-        drop(weak);
-    }
 }

objc2/src/rc/mod.rs

@@ -60,21 +60,51 @@
 
 mod autorelease;
 mod id;
+mod ownership;
 mod strong;
 mod weak;
+mod weak_id;
 
 pub use self::autorelease::{autoreleasepool, AutoreleasePool, AutoreleaseSafe};
-pub use self::id::{Id, Owned, Ownership, ShareId, Shared, WeakId};
+pub use self::id::{Id, ShareId};
+pub use self::ownership::{Owned, Ownership, Shared};
 pub use self::strong::StrongPtr;
 pub use self::weak::WeakPtr;
+pub use self::weak_id::WeakId;
 
 // These tests use NSObject, which isn't present for GNUstep
 #[cfg(all(test, target_vendor = "apple"))]
 mod tests {
+    use core::mem::size_of;
+
     use super::autoreleasepool;
     use super::StrongPtr;
+    use super::{Id, Owned, Shared, WeakId};
     use crate::runtime::Object;
 
+    pub struct TestType {
+        _data: [u8; 0], // TODO: `UnsafeCell`?
+    }
+
+    #[test]
+    fn test_size_of() {
+        assert_eq!(size_of::<Id<TestType, Owned>>(), size_of::<&TestType>());
+        assert_eq!(size_of::<Id<TestType, Shared>>(), size_of::<&TestType>());
+        assert_eq!(
+            size_of::<Option<Id<TestType, Owned>>>(),
+            size_of::<&TestType>()
+        );
+        assert_eq!(
+            size_of::<Option<Id<TestType, Shared>>>(),
+            size_of::<&TestType>()
+        );
+
+        assert_eq!(
+            size_of::<Option<WeakId<TestType>>>(),
+            size_of::<*const ()>()
+        );
+    }
+
     #[test]
     fn test_strong_clone() {
         fn retain_count(obj: *mut Object) -> usize {

objc2/src/rc/ownership.rs

@@ -0,0 +1,24 @@
+/// A type used to mark that a struct owns the object(s) it contains,
+/// so it has the sole references to them.
+pub enum Owned {}
+
+/// A type used to mark that the object(s) a struct contains are shared,
+/// so there may be other references to them.
+pub enum Shared {}
+
+mod private {
+    pub trait Sealed {}
+
+    impl Sealed for super::Owned {}
+    impl Sealed for super::Shared {}
+}
+
+/// A type that marks what type of ownership a struct has over the object(s)
+/// it contains; specifically, either [`Owned`] or [`Shared`].
+///
+/// This trait is sealed and not meant to be implemented outside of the this
+/// crate.
+pub trait Ownership: private::Sealed + 'static {}
+
+impl Ownership for Owned {}
+impl Ownership for Shared {}