From 06a8d59ded67dfaa589112ceb8a8e031bc575249 Mon Sep 17 00:00:00 2001
From: Colin Sherratt <colin.sherratt@gmail.com>
Date: Mon, 30 Dec 2013 19:17:35 -0500
Subject: Add a copy-on-write container.

---
 src/libstd/sync/arc.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'src/libstd/sync')

diff --git a/src/libstd/sync/arc.rs b/src/libstd/sync/arc.rs
index 7b94a3acc2b..5c452018b9b 100644
--- a/src/libstd/sync/arc.rs
+++ b/src/libstd/sync/arc.rs
@@ -94,6 +94,14 @@ impl<T: Send> UnsafeArc<T> {
             return &(*self.data).data as *T;
         }
     }
+
+    /// checks if this is the only reference to the arc protected data
+    #[inline]
+    pub fn is_owned(&self) -> bool {
+        unsafe {
+            (*self.data).count.load(Relaxed) == 1
+        }
+    }
 }
 
 impl<T: Send> Clone for UnsafeArc<T> {
-- 
cgit 1.4.1-3-g733a5