From 7b89bd7ccacd0908d7e22a5cf383c8cc147bc3d5 Mon Sep 17 00:00:00 2001
From: Amanieu d'Antras <amanieu@gmail.com>
Date: Fri, 31 Mar 2017 13:52:46 +0100
Subject: Add ptr::offset_to

---
 src/libcore/slice/mod.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

(limited to 'src/libcore/slice')

diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index af492b3c639..5a978ccc741 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -1502,9 +1502,10 @@ unsafe impl<'a, T> TrustedLen for IterMut<'a, T> {}
 // Return the arithmetic difference if `T` is zero size.
 #[inline(always)]
 fn ptrdistance<T>(start: *const T, end: *const T) -> usize {
-    let diff = (end as usize).wrapping_sub(start as usize);
-    let size = mem::size_of::<T>();
-    diff / (if size == 0 { 1 } else { size })
+    match start.offset_to(end) {
+        Some(x) => x as usize,
+        None => (end as usize).wrapping_sub(start as usize),
+    }
 }
 
 // Extension methods for raw pointers, used by the iterators
-- 
cgit 1.4.1-3-g733a5