Mark `MutBuf::mut_buf` as unsafe

`MutBuf::mut_buf` allows access to uninitialized memory.

src/buf/byte.rs

@@ -321,7 +321,7 @@ impl MutBuf for MutByteBuf {
         self.buf.advance(cnt)
     }
 
-    fn mut_bytes<'a>(&'a mut self) -> &'a mut [u8] {
+    unsafe fn mut_bytes<'a>(&'a mut self) -> &'a mut [u8] {
         let pos = self.buf.pos();
         let lim = self.buf.lim();
         &mut self.buf.mem.bytes_mut()[pos..lim]

src/buf/mod.rs

@@ -102,7 +102,9 @@ pub trait MutBuf : Sized {
 
     /// Returns a mutable slice starting at the current MutBuf position and of
     /// length between 0 and `MutBuf::remaining()`.
-    fn mut_bytes<'a>(&'a mut self) -> &'a mut [u8];
+    ///
+    /// The returned byte slice may represent uninitialized memory.
+    unsafe fn mut_bytes<'a>(&'a mut self) -> &'a mut [u8];
 
     /// Write bytes from the given slice into the `MutBuf` and advance the
     /// cursor by the number of bytes written.
@@ -268,7 +270,7 @@ impl<'a, R: io::Read+'a> Source for &'a mut R {
         let mut cnt = 0;
 
         while buf.has_remaining() {
-            let i = try!(self.read(buf.mut_bytes()));
+            let i = try!(self.read(unsafe { buf.mut_bytes() }));
 
             if i == 0 {
                 break;
@@ -349,7 +351,7 @@ impl MutBuf for Vec<u8> {
         }
     }
 
-    fn mut_bytes(&mut self) -> &mut [u8] {
+    unsafe fn mut_bytes(&mut self) -> &mut [u8] {
         use std::slice;
 
         if self.capacity() == self.len() {
@@ -359,10 +361,8 @@ impl MutBuf for Vec<u8> {
         let cap = self.capacity();
         let len = self.len();
 
-        unsafe {
-            let ptr = self.as_mut_ptr();
-            &mut slice::from_raw_parts_mut(ptr, cap)[len..]
-        }
+        let ptr = self.as_mut_ptr();
+        &mut slice::from_raw_parts_mut(ptr, cap)[len..]
     }
 }
 

src/buf/ring.rs

@@ -196,7 +196,7 @@ impl MutBuf for RingBuf {
         self.advance_writer(cnt)
     }
 
-    fn mut_bytes(&mut self) -> &mut [u8] {
+    unsafe fn mut_bytes(&mut self) -> &mut [u8] {
         if self.cap == 0 {
             return self.ptr.bytes_mut();
         }

src/buf/slice.rs

@@ -53,7 +53,7 @@ impl<'a> MutBuf for MutSliceBuf<'a> {
         self.pos += cnt;
     }
 
-    fn mut_bytes<'b>(&'b mut self) -> &'b mut [u8] {
+    unsafe fn mut_bytes<'b>(&'b mut self) -> &'b mut [u8] {
         &mut self.bytes[self.pos..]
     }
 }

src/str/bytes.rs

@@ -208,17 +208,15 @@ impl<'a> Source for &'a Bytes {
         while src.has_remaining() && dst.has_remaining() {
             let l;
 
-            {
+            unsafe {
                 let s = src.bytes();
                 let d = dst.mut_bytes();
                 l = cmp::min(s.len(), d.len());
 
-                unsafe {
-                    ptr::copy_nonoverlapping(
-                        s.as_ptr(),
-                        d.as_mut_ptr(),
-                        l);
-                }
+                ptr::copy_nonoverlapping(
+                    s.as_ptr(),
+                    d.as_mut_ptr(),
+                    l);
             }
 
             src.advance(l);

test/test_buf.rs

@@ -30,7 +30,10 @@ pub fn test_vec_as_mut_buf() {
     let mut buf = vec![];
 
     assert_eq!(buf.remaining(), usize::MAX);
-    assert_eq!(buf.mut_bytes().len(), 64);
+
+    unsafe {
+        assert_eq!(buf.mut_bytes().len(), 64);
+    }
 
     buf.write(&b"zomg"[..]).unwrap();