fill and try_fill: do byte swap per slice element, not per byte

Author: dhardy

src/lib.rs

@@ -501,11 +501,8 @@ pub trait Rng {
     /// 
     /// [`ErrorKind`]: enum.ErrorKind.html
     fn fill<T: AsByteSliceMut + ?Sized>(&mut self, dest: &mut T) where Self: Sized {
-        let slice = dest.as_byte_slice_mut();
-        self.fill_bytes(slice);
-        for mut x in slice {
-            x.to_le();
-        }
+        self.fill_bytes(dest.as_byte_slice_mut());
+        dest.to_le();
     }
 
     /// Fill `dest` entirely with random data.
@@ -535,11 +532,8 @@ pub trait Rng {
     /// 
     /// [`ErrorKind`]: enum.ErrorKind.html
     fn try_fill<T: AsByteSliceMut + ?Sized>(&mut self, dest: &mut T) -> Result<(), Error> where Self: Sized {
-        let slice = dest.as_byte_slice_mut();
-        self.try_fill_bytes(slice)?;
-        for mut x in slice {
-            x.to_le();
-        }
+        self.try_fill_bytes(dest.as_byte_slice_mut())?;
+        dest.to_le();
         Ok(())
     }
 
@@ -766,12 +760,17 @@ impl<R: ?Sized> Rng for Box<R> where R: Rng {
 pub trait AsByteSliceMut {
     /// Return a mutable reference to self as a byte slice
     fn as_byte_slice_mut<'a>(&'a mut self) -> &'a mut [u8];
+    
+    /// Call `to_le` on each element (i.e. byte-swap on Big Endian platforms).
+    fn to_le(&mut self);
 }
 
 impl AsByteSliceMut for [u8] {
     fn as_byte_slice_mut<'a>(&'a mut self) -> &'a mut [u8] {
         self
     }
+    
+    fn to_le(&mut self) {}
 }
 
 macro_rules! impl_as_byte_slice {
@@ -786,6 +785,12 @@ macro_rules! impl_as_byte_slice {
                     )
                 }
             }
+            
+            fn to_le(&mut self) {
+                for mut x in self {
+                    *x = x.to_le();
+                }
+            }
         }
     }
 }