Change BufMut methods that expose maybe-uninitialized bytes (#305)

- The return type of `BufMut::bytes_mut` is now
  `&mut [MaybeUninit<u8>]`.
- The argument type of `BufMut::bytes_vectored_mut` is now
  `&mut [bytes::buf::IoSliceMut]`.
- `bytes::buf::IoSliceMut` is a `repr(transparent)` wrapper around an
  `std::io::IoSliceMut`, but does not expose the inner bytes with a safe
  API, since they might be uninitialized.
- `BufMut::bytesMut` and `BufMut::bytes_vectored_mut` are no longer
  `unsafe fn`, since the types encapsulate the unsafety instead.

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/test_bytes.rs b/tests/test_bytes.rs
index 212189e..9fa8019 100644
--- a/tests/test_bytes.rs
+++ b/tests/test_bytes.rs
@@ -465,6 +465,16 @@ fn extend_from_slice_mut() {
 }
 
 #[test]
+fn extend_mut_without_size_hint() {
+    let mut bytes = BytesMut::with_capacity(0);
+    let mut long_iter = LONG.iter();
+
+    // Use iter::from_fn since it doesn't know a size_hint
+    bytes.extend(std::iter::from_fn(|| long_iter.next()));
+    assert_eq!(*bytes, LONG[..]);
+}
+
+#[test]
 fn from_static() {
     let mut a = Bytes::from_static(b"ab");
     let b = a.split_off(1);