3 files changed, 18 insertions, 0 deletions
diff --git a/src/libstd/sys/redox/os_str.rs b/src/libstd/sys/redox/os_str.rs
index 474d59eed83..c2bba07f68c 100644
--- a/src/libstd/sys/redox/os_str.rs
+++ b/src/libstd/sys/redox/os_str.rs
@@ -104,6 +104,12 @@ impl Buf {
     pub fn into_box(self) -> Box<Slice> {
         unsafe { mem::transmute(self.inner.into_boxed_slice()) }
     }
+
+    #[inline]
+    pub fn from_box(boxed: Box<Slice>) -> Buf {
+        let inner: Box<[u8]> = unsafe { mem::transmute(boxed) };
+        Buf { inner: inner.into_vec() }
+    }
 }
 
 impl Slice {
diff --git a/src/libstd/sys/unix/os_str.rs b/src/libstd/sys/unix/os_str.rs
index c27599ec020..f5b942d3343 100644
--- a/src/libstd/sys/unix/os_str.rs
+++ b/src/libstd/sys/unix/os_str.rs
@@ -104,6 +104,12 @@ impl Buf {
     pub fn into_box(self) -> Box<Slice> {
         unsafe { mem::transmute(self.inner.into_boxed_slice()) }
     }
+
+    #[inline]
+    pub fn from_box(boxed: Box<Slice>) -> Buf {
+        let inner: Box<[u8]> = unsafe { mem::transmute(boxed) };
+        Buf { inner: inner.into_vec() }
+    }
 }
 
 impl Slice {
diff --git a/src/libstd/sys/windows/os_str.rs b/src/libstd/sys/windows/os_str.rs
index b02b06e1ef2..f401e7b35c8 100644
--- a/src/libstd/sys/windows/os_str.rs
+++ b/src/libstd/sys/windows/os_str.rs
@@ -97,6 +97,12 @@ impl Buf {
     pub fn into_box(self) -> Box<Slice> {
         unsafe { mem::transmute(self.inner.into_box()) }
     }
+
+    #[inline]
+    pub fn from_box(boxed: Box<Slice>) -> Buf {
+        let inner: Box<Wtf8> = unsafe { mem::transmute(boxed) };
+        Buf { inner: Wtf8Buf::from_box(inner) }
+    }
 }
 
 impl Slice {