From a5e8bbf32b32ed7d3b06149fdfa0977c0ec0a22e Mon Sep 17 00:00:00 2001
From: Charlie Fan <changchu@synopsys.com>
Date: Fri, 10 Feb 2017 16:38:59 +0800
Subject: [PATCH] Add `swap` method for `Cell`

---
 src/libcore/cell.rs | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
index ab44342ebf02..d130b0279a20 100644
--- a/src/libcore/cell.rs
+++ b/src/libcore/cell.rs
@@ -186,6 +186,7 @@ use fmt::{self, Debug, Display};
 use marker::Unsize;
 use mem;
 use ops::{Deref, DerefMut, CoerceUnsized};
+use ptr;
 
 /// A mutable memory location.
 ///
@@ -387,6 +388,32 @@ impl<T> Cell<T> {
         drop(old);
     }
 
+    /// Swaps the values of two Cells.
+    /// Difference with `std::mem::swap` is that this function doesn't require `&mut` reference.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(move_cell)]
+    /// use std::cell::Cell;
+    ///
+    /// let c1 = Cell::new(5i32);
+    /// let c2 = Cell::new(10i32);
+    /// c1.swap(&c2);
+    /// assert_eq!(10, c1.get());
+    /// assert_eq!(5, c2.get());
+    /// ```
+    #[inline]
+    #[unstable(feature = "move_cell", issue = "39264")]
+    pub fn swap(&self, other: &Self) {
+        if ptr::eq(self, other) {
+            return;
+        }
+        unsafe {
+            ptr::swap(self.value.get(), other.value.get());
+        }
+    }
+
     /// Replaces the contained value.
     ///
     /// # Examples