From 678f6382b86646269c535a616aa7a8cc0e6d5ab4 Mon Sep 17 00:00:00 2001
From: Sven Marnach <sven@marnach.net>
Date: Thu, 4 Oct 2018 20:03:43 +0200
Subject: [PATCH] io: implement prepare_uninitialized_buffer for Take and Chain
 (#678)

---
 tokio-io/src/async_write.rs | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/tokio-io/src/async_write.rs b/tokio-io/src/async_write.rs
index 245bea7e5..6fcf418a0 100644
--- a/tokio-io/src/async_write.rs
+++ b/tokio-io/src/async_write.rs
@@ -172,17 +172,22 @@ impl AsyncWrite for std_io::Sink {
     }
 }
 
-// TODO: Implement `prepare_uninitialized_buffer` for `io::Take`.
-// This is blocked on rust-lang/rust#27269
 impl<T: AsyncRead> AsyncRead for std_io::Take<T> {
+    unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
+        self.get_ref().prepare_uninitialized_buffer(buf)
+    }
 }
 
-// TODO: Implement `prepare_uninitialized_buffer` when upstream exposes inner
-// parts
 impl<T, U> AsyncRead for std_io::Chain<T, U>
     where T: AsyncRead,
           U: AsyncRead,
 {
+    unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
+        let (t, u) = self.get_ref();
+        // We don't need to execute the second initializer if the first one
+        // already zeroed the buffer out.
+        t.prepare_uninitialized_buffer(buf) || u.prepare_uninitialized_buffer(buf)
+    }
 }
 
 impl<T: AsyncWrite> AsyncWrite for std_io::BufWriter<T> {