1 files changed, 160 insertions, 0 deletions
diff --git a/src/libcore/pin.rs b/src/libcore/pin.rs
new file mode 100644
index 00000000000..e9001f86b35
--- /dev/null
+++ b/src/libcore/pin.rs
@@ -0,0 +1,160 @@
+//! Types which pin data to its location in memory
+//!
+//! See the [standard library module] for more information.
+//!
+//! [standard library module]: ../../std/pin/index.html
+
+#![unstable(feature = "pin", issue = "49150")]
+
+use fmt;
+use future::{Future, UnsafeFutureObj};
+use marker::{Sized, Unpin, Unsize};
+use task::{Context, Poll};
+use ops::{Deref, DerefMut, CoerceUnsized};
+
+/// A pinned reference.
+///
+/// This type is similar to a mutable reference, except that it pins its value,
+/// which prevents it from moving out of the reference, unless it implements [`Unpin`].
+///
+/// See the [`pin` module] documentation for furthur explanation on pinning.
+///
+/// [`Unpin`]: ../../std/marker/trait.Unpin.html
+/// [`pin` module]: ../../std/pin/index.html
+#[unstable(feature = "pin", issue = "49150")]
+#[fundamental]
+pub struct PinMut<'a, T: ?Sized + 'a> {
+    inner: &'a mut T,
+}
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: ?Sized + Unpin> PinMut<'a, T> {
+    /// Construct a new `PinMut` around a reference to some data of a type that
+    /// implements `Unpin`.
+    #[unstable(feature = "pin", issue = "49150")]
+    pub fn new(reference: &'a mut T) -> PinMut<'a, T> {
+        PinMut { inner: reference }
+    }
+
+    /// Get a mutable reference to the data inside of this `PinMut`.
+    #[unstable(feature = "pin", issue = "49150")]
+    pub fn get_mut(this: PinMut<'a, T>) -> &'a mut T {
+        this.inner
+    }
+}
+
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: ?Sized> PinMut<'a, T> {
+    /// Construct a new `PinMut` around a reference to some data of a type that
+    /// may or may not implement `Unpin`.
+    ///
+    /// This constructor is unsafe because we do not know what will happen with
+    /// that data after the lifetime of the reference ends. If you cannot guarantee that the
+    /// data will never move again, calling this constructor is invalid.
+    #[unstable(feature = "pin", issue = "49150")]
+    pub unsafe fn new_unchecked(reference: &'a mut T) -> PinMut<'a, T> {
+        PinMut { inner: reference }
+    }
+
+    /// Reborrow a `PinMut` for a shorter lifetime.
+    ///
+    /// For example, `PinMut::get_mut(x.reborrow())` (unsafely) returns a
+    /// short-lived mutable reference reborrowing from `x`.
+    #[unstable(feature = "pin", issue = "49150")]
+    pub fn reborrow<'b>(&'b mut self) -> PinMut<'b, T> {
+        PinMut { inner: self.inner }
+    }
+
+    /// Get a mutable reference to the data inside of this `PinMut`.
+    ///
+    /// This function is unsafe. You must guarantee that you will never move
+    /// the data out of the mutable reference you receive when you call this
+    /// function.
+    #[unstable(feature = "pin", issue = "49150")]
+    pub unsafe fn get_mut_unchecked(this: PinMut<'a, T>) -> &'a mut T {
+        this.inner
+    }
+
+    /// Construct a new pin by mapping the interior value.
+    ///
+    /// For example, if you  wanted to get a `PinMut` of a field of something,
+    /// you could use this to get access to that field in one line of code.
+    ///
+    /// This function is unsafe. You must guarantee that the data you return
+    /// will not move so long as the argument value does not move (for example,
+    /// because it is one of the fields of that value), and also that you do
+    /// not move out of the argument you receive to the interior function.
+    #[unstable(feature = "pin", issue = "49150")]
+    pub unsafe fn map_unchecked<U, F>(this: PinMut<'a, T>, f: F) -> PinMut<'a, U> where
+        F: FnOnce(&mut T) -> &mut U
+    {
+        PinMut { inner: f(this.inner) }
+    }
+
+    /// Assign a new value to the memory behind the pinned reference.
+    #[unstable(feature = "pin", issue = "49150")]
+    pub fn set(this: PinMut<'a, T>, value: T)
+        where T: Sized,
+    {
+        *this.inner = value;
+    }
+}
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: ?Sized> Deref for PinMut<'a, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &*self.inner
+    }
+}
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: ?Sized + Unpin> DerefMut for PinMut<'a, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        self.inner
+    }
+}
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: fmt::Debug + ?Sized> fmt::Debug for PinMut<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: fmt::Display + ?Sized> fmt::Display for PinMut<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&**self, f)
+    }
+}
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: ?Sized> fmt::Pointer for PinMut<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Pointer::fmt(&(&*self.inner as *const T), f)
+    }
+}
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<PinMut<'a, U>> for PinMut<'a, T> {}
+
+#[unstable(feature = "pin", issue = "49150")]
+impl<'a, T: ?Sized> Unpin for PinMut<'a, T> {}
+
+#[unstable(feature = "futures_api", issue = "50547")]
+unsafe impl<'a, T, F> UnsafeFutureObj<'a, T> for PinMut<'a, F>
+    where F: Future<Output = T> + 'a
+{
+    fn into_raw(self) -> *mut () {
+        unsafe { PinMut::get_mut_unchecked(self) as *mut F as *mut () }
+    }
+
+    unsafe fn poll(ptr: *mut (), cx: &mut Context) -> Poll<T> {
+        PinMut::new_unchecked(&mut *(ptr as *mut F)).poll(cx)
+    }
+
+    unsafe fn drop(_ptr: *mut ()) {}
+}