4 files changed, 276 insertions, 0 deletions
diff --git a/third_party/rust/objc/src/rc/autorelease.rs b/third_party/rust/objc/src/rc/autorelease.rs
new file mode 100644
index 0000000000..ad7a5e2847
--- /dev/null
+++ b/third_party/rust/objc/src/rc/autorelease.rs
@@ -0,0 +1,30 @@
+use std::os::raw::c_void;
+use runtime::{objc_autoreleasePoolPush, objc_autoreleasePoolPop};
+
+// we use a struct to ensure that objc_autoreleasePoolPop during unwinding.
+struct AutoReleaseHelper {
+    context: *mut c_void,
+}
+
+impl AutoReleaseHelper {
+    unsafe fn new() -> Self {
+        AutoReleaseHelper { context: objc_autoreleasePoolPush() }
+    }
+}
+
+impl Drop for AutoReleaseHelper {
+    fn drop(&mut self) {
+        unsafe { objc_autoreleasePoolPop(self.context) }
+    }
+}
+
+/**
+Execute `f` in the context of a new autorelease pool. The pool is drained
+after the execution of `f` completes.
+
+This corresponds to `@autoreleasepool` blocks in Objective-C and Swift.
+*/
+pub fn autoreleasepool<T, F: FnOnce() -> T>(f: F) -> T {
+    let _context = unsafe { AutoReleaseHelper::new() };
+    f()
+}
diff --git a/third_party/rust/objc/src/rc/mod.rs b/third_party/rust/objc/src/rc/mod.rs
new file mode 100644
index 0000000000..f6d26f7a1b
--- /dev/null
+++ b/third_party/rust/objc/src/rc/mod.rs
@@ -0,0 +1,123 @@
+/*!
+Utilities for reference counting Objective-C objects.
+
+The utilities of the `rc` module provide ARC-like semantics for working with
+Objective-C's reference counted objects in Rust.
+A `StrongPtr` retains an object and releases the object when dropped.
+A `WeakPtr` will not retain the object, but can be upgraded to a `StrongPtr`
+and safely fails if the object has been deallocated.
+
+These utilities are not intended to provide a fully safe interface, but can be
+useful when writing higher-level Rust wrappers for Objective-C code.
+
+For more information on Objective-C's reference counting, see Apple's documentation:
+<https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/MemoryMgmt/Articles/MemoryMgmt.html>
+
+# Example
+
+``` no_run
+# #[macro_use] extern crate objc;
+# use objc::rc::{autoreleasepool, StrongPtr};
+# fn main() {
+// StrongPtr will release the object when dropped
+let obj = unsafe {
+    StrongPtr::new(msg_send![class!(NSObject), new])
+};
+
+// Cloning retains the object an additional time
+let cloned = obj.clone();
+autoreleasepool(|| {
+    // Autorelease consumes the StrongPtr, but won't
+    // actually release until the end of an autoreleasepool
+    cloned.autorelease();
+});
+
+// Weak references won't retain the object
+let weak = obj.weak();
+drop(obj);
+assert!(weak.load().is_null());
+# }
+```
+*/
+
+mod strong;
+mod weak;
+mod autorelease;
+
+pub use self::strong::StrongPtr;
+pub use self::weak::WeakPtr;
+pub use self::autorelease::autoreleasepool;
+
+// These tests use NSObject, which isn't present for GNUstep
+#[cfg(all(test, any(target_os = "macos", target_os = "ios")))]
+mod tests {
+    use runtime::Object;
+    use super::StrongPtr;
+    use super::autoreleasepool;
+
+    #[test]
+    fn test_strong_clone() {
+        fn retain_count(obj: *mut Object) -> usize {
+            unsafe { msg_send![obj, retainCount] }
+        }
+
+        let obj = unsafe {
+            StrongPtr::new(msg_send![class!(NSObject), new])
+        };
+        assert!(retain_count(*obj) == 1);
+
+        let cloned = obj.clone();
+        assert!(retain_count(*cloned) == 2);
+        assert!(retain_count(*obj) == 2);
+
+        drop(obj);
+        assert!(retain_count(*cloned) == 1);
+    }
+
+    #[test]
+    fn test_weak() {
+        let obj = unsafe {
+            StrongPtr::new(msg_send![class!(NSObject), new])
+        };
+        let weak = obj.weak();
+
+        let strong = weak.load();
+        assert!(*strong == *obj);
+        drop(strong);
+
+        drop(obj);
+        assert!(weak.load().is_null());
+    }
+
+    #[test]
+    fn test_weak_copy() {
+        let obj = unsafe {
+            StrongPtr::new(msg_send![class!(NSObject), new])
+        };
+        let weak = obj.weak();
+
+        let weak2 = weak.clone();
+        let strong = weak2.load();
+        assert!(*strong == *obj);
+    }
+
+    #[test]
+    fn test_autorelease() {
+        let obj = unsafe {
+            StrongPtr::new(msg_send![class!(NSObject), new])
+        };
+
+        fn retain_count(obj: *mut Object) -> usize {
+            unsafe { msg_send![obj, retainCount] }
+        }
+        let cloned = obj.clone();
+
+        autoreleasepool(|| {
+                        obj.autorelease();
+                        assert!(retain_count(*cloned) == 2);
+        });
+
+        // make sure that the autoreleased value has been released
+        assert!(retain_count(*cloned) == 1);
+    }
+}
diff --git a/third_party/rust/objc/src/rc/strong.rs b/third_party/rust/objc/src/rc/strong.rs
new file mode 100644
index 0000000000..a61881b6ff
--- /dev/null
+++ b/third_party/rust/objc/src/rc/strong.rs
@@ -0,0 +1,73 @@
+use std::fmt;
+use std::mem;
+use std::ops::Deref;
+
+use runtime::{Object, self};
+use super::WeakPtr;
+
+/// A pointer that strongly references an object, ensuring it won't be deallocated.
+pub struct StrongPtr(*mut Object);
+
+impl StrongPtr {
+    /// Constructs a `StrongPtr` to a newly created object that already has a
+    /// +1 retain count. This will not retain the object.
+    /// When dropped, the object will be released.
+    /// Unsafe because the caller must ensure the given object pointer is valid.
+    pub unsafe fn new(ptr: *mut Object) -> Self {
+        StrongPtr(ptr)
+    }
+
+    /// Retains the given object and constructs a `StrongPtr` to it.
+    /// When dropped, the object will be released.
+    /// Unsafe because the caller must ensure the given object pointer is valid.
+    pub unsafe fn retain(ptr: *mut Object) -> Self {
+        StrongPtr(runtime::objc_retain(ptr))
+    }
+
+    /// Autoreleases self, meaning that the object is not immediately released,
+    /// but will be when the autorelease pool is drained. A pointer to the
+    /// object is returned, but its validity is no longer ensured.
+    pub fn autorelease(self) -> *mut Object {
+        let ptr = self.0;
+        mem::forget(self);
+        unsafe {
+            runtime::objc_autorelease(ptr);
+        }
+        ptr
+    }
+
+    /// Returns a `WeakPtr` to self.
+    pub fn weak(&self) -> WeakPtr {
+        unsafe { WeakPtr::new(self.0) }
+    }
+}
+
+impl Drop for StrongPtr {
+    fn drop(&mut self) {
+        unsafe {
+            runtime::objc_release(self.0);
+        }
+    }
+}
+
+impl Clone for StrongPtr {
+    fn clone(&self) -> StrongPtr {
+        unsafe {
+            StrongPtr::retain(self.0)
+        }
+    }
+}
+
+impl Deref for StrongPtr {
+    type Target = *mut Object;
+
+    fn deref(&self) -> &*mut Object {
+        &self.0
+    }
+}
+
+impl fmt::Pointer for StrongPtr {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Pointer::fmt(&self.0, f)
+    }
+}
diff --git a/third_party/rust/objc/src/rc/weak.rs b/third_party/rust/objc/src/rc/weak.rs
new file mode 100644
index 0000000000..289bd8dedb
--- /dev/null
+++ b/third_party/rust/objc/src/rc/weak.rs
@@ -0,0 +1,50 @@
+use std::cell::UnsafeCell;
+use std::ptr;
+
+use runtime::{Object, self};
+use super::StrongPtr;
+
+// Our pointer must have the same address even if we are moved, so Box it.
+// Although loading the WeakPtr may modify the pointer, it is thread safe,
+// so we must use an UnsafeCell to get a *mut without self being mutable.
+
+/// A pointer that weakly references an object, allowing to safely check
+/// whether it has been deallocated.
+pub struct WeakPtr(Box<UnsafeCell<*mut Object>>);
+
+impl WeakPtr {
+    /// Constructs a `WeakPtr` to the given object.
+    /// Unsafe because the caller must ensure the given object pointer is valid.
+    pub unsafe fn new(obj: *mut Object) -> Self {
+        let ptr = Box::new(UnsafeCell::new(ptr::null_mut()));
+        runtime::objc_initWeak(ptr.get(), obj);
+        WeakPtr(ptr)
+    }
+
+    /// Loads the object self points to, returning a `StrongPtr`.
+    /// If the object has been deallocated, the returned pointer will be null.
+    pub fn load(&self) -> StrongPtr {
+        unsafe {
+            let ptr = runtime::objc_loadWeakRetained(self.0.get());
+            StrongPtr::new(ptr)
+        }
+    }
+}
+
+impl Drop for WeakPtr {
+    fn drop(&mut self) {
+        unsafe {
+            runtime::objc_destroyWeak(self.0.get());
+        }
+    }
+}
+
+impl Clone for WeakPtr {
+    fn clone(&self) -> Self {
+        let ptr = Box::new(UnsafeCell::new(ptr::null_mut()));
+        unsafe {
+            runtime::objc_copyWeak(ptr.get(), self.0.get());
+        }
+        WeakPtr(ptr)
+    }
+}