Fix incorrect prepare_uninitialized_buffer

Cargo.toml

@@ -24,6 +24,7 @@ webpki = "0.21"
 [features]
 early-data = []
 dangerous_configuration = ["rustls/dangerous_configuration"]
+unstable = []
 
 [dev-dependencies]
 tokio = { version = "0.2.0", features = ["macros", "net", "io-util", "rt-core", "time"] }

src/client.rs

@@ -69,8 +69,9 @@ impl<IO> AsyncRead for TlsStream<IO>
 where
     IO: AsyncRead + AsyncWrite + Unpin,
 {
+    #[cfg(feature = "unstable")]
     unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [std::mem::MaybeUninit<u8>]) -> bool {
-        self.io.prepare_uninitialized_buffer(buf)
+        false
     }
 
     fn poll_read(self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut [u8]) -> Poll<io::Result<usize>> {

src/server.rs

@@ -67,8 +67,12 @@ impl<IO> AsyncRead for TlsStream<IO>
 where
     IO: AsyncRead + AsyncWrite + Unpin,
 {
+    #[cfg(feature = "unstable")]
     unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [std::mem::MaybeUninit<u8>]) -> bool {
-        self.io.prepare_uninitialized_buffer(buf)
+        // TODO
+        //
+        // https://doc.rust-lang.org/nightly/std/io/trait.Read.html#method.initializer
+        false
     }
 
     fn poll_read(self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut [u8]) -> Poll<io::Result<usize>> {