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diff --git a/third_party/rust/tokio-io/src/async_read.rs b/third_party/rust/tokio-io/src/async_read.rs
new file mode 100644
index 0000000000..3c2c3bab09
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+++ b/third_party/rust/tokio-io/src/async_read.rs
@@ -0,0 +1,168 @@
+use std::io as std_io;
+use bytes::BufMut;
+use futures::{Async, Poll};
+
+use {framed, split, AsyncWrite};
+#[allow(deprecated)]
+use codec::{Decoder, Encoder, Framed};
+use split::{ReadHalf, WriteHalf};
+
+/// Read bytes asynchronously.
+///
+/// This trait inherits from `std::io::Read` and indicates that an I/O object is
+/// **non-blocking**. All non-blocking I/O objects must return an error when
+/// bytes are unavailable instead of blocking the current thread.
+///
+/// Specifically, this means that the `read` function will return one of the
+/// following:
+///
+/// * `Ok(n)` means that `n` bytes of data was immediately read and placed into
+///   the output buffer, where `n` == 0 implies that EOF has been reached.
+///
+/// * `Err(e) if e.kind() == ErrorKind::WouldBlock` means that no data was read
+///   into the buffer provided. The I/O object is not currently readable but may
+///   become readable in the future. Most importantly, **the current future's
+///   task is scheduled to get unparked when the object is readable**. This
+///   means that like `Future::poll` you'll receive a notification when the I/O
+///   object is readable again.
+///
+/// * `Err(e)` for other errors are standard I/O errors coming from the
+///   underlying object.
+///
+/// This trait importantly means that the `read` method only works in the
+/// context of a future's task. The object may panic if used outside of a task.
+pub trait AsyncRead: std_io::Read {
+    /// Prepares an uninitialized buffer to be safe to pass to `read`. Returns
+    /// `true` if the supplied buffer was zeroed out.
+    ///
+    /// While it would be highly unusual, implementations of [`io::Read`] are
+    /// able to read data from the buffer passed as an argument. Because of
+    /// this, the buffer passed to [`io::Read`] must be initialized memory. In
+    /// situations where large numbers of buffers are used, constantly having to
+    /// zero out buffers can be expensive.
+    ///
+    /// This function does any necessary work to prepare an uninitialized buffer
+    /// to be safe to pass to `read`. If `read` guarantees to never attempt read
+    /// data out of the supplied buffer, then `prepare_uninitialized_buffer`
+    /// doesn't need to do any work.
+    ///
+    /// If this function returns `true`, then the memory has been zeroed out.
+    /// This allows implementations of `AsyncRead` which are composed of
+    /// multiple sub implementations to efficiently implement
+    /// `prepare_uninitialized_buffer`.
+    ///
+    /// This function isn't actually `unsafe` to call but `unsafe` to implement.
+    /// The implementor must ensure that either the whole `buf` has been zeroed
+    /// or `read_buf()` overwrites the buffer without reading it and returns
+    /// correct value.
+    ///
+    /// This function is called from [`read_buf`].
+    ///
+    /// [`io::Read`]: https://doc.rust-lang.org/std/io/trait.Read.html
+    /// [`read_buf`]: #method.read_buf
+    unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
+        for i in 0..buf.len() {
+            buf[i] = 0;
+        }
+
+        true
+    }
+
+    /// Attempt to read from the `AsyncRead` into `buf`.
+    ///
+    /// On success, returns `Ok(Async::Ready(num_bytes_read))`.
+    ///
+    /// If no data is available for reading, the method returns
+    /// `Ok(Async::Pending)` and arranges for the current task (via
+    /// `cx.waker()`) to receive a notification when the object becomes
+    /// readable or is closed.
+    fn poll_read(&mut self, buf: &mut [u8]) -> Poll<usize, std_io::Error> {
+        match self.read(buf) {
+            Ok(t) => Ok(Async::Ready(t)),
+            Err(ref e) if e.kind() == std_io::ErrorKind::WouldBlock => {
+                return Ok(Async::NotReady)
+            }
+            Err(e) => return Err(e.into()),
+        }
+    }
+
+    /// Pull some bytes from this source into the specified `Buf`, returning
+    /// how many bytes were read.
+    ///
+    /// The `buf` provided will have bytes read into it and the internal cursor
+    /// will be advanced if any bytes were read. Note that this method typically
+    /// will not reallocate the buffer provided.
+    fn read_buf<B: BufMut>(&mut self, buf: &mut B) -> Poll<usize, std_io::Error>
+        where Self: Sized,
+    {
+        if !buf.has_remaining_mut() {
+            return Ok(Async::Ready(0));
+        }
+
+        unsafe {
+            let n = {
+                let b = buf.bytes_mut();
+
+                self.prepare_uninitialized_buffer(b);
+
+                try_ready!(self.poll_read(b))
+            };
+
+            buf.advance_mut(n);
+            Ok(Async::Ready(n))
+        }
+    }
+
+    /// Provides a `Stream` and `Sink` interface for reading and writing to this
+    /// `Io` object, using `Decode` and `Encode` to read and write the raw data.
+    ///
+    /// Raw I/O objects work with byte sequences, but higher-level code usually
+    /// wants to batch these into meaningful chunks, called "frames". This
+    /// method layers framing on top of an I/O object, by using the `Codec`
+    /// traits to handle encoding and decoding of messages frames. Note that
+    /// the incoming and outgoing frame types may be distinct.
+    ///
+    /// This function returns a *single* object that is both `Stream` and
+    /// `Sink`; grouping this into a single object is often useful for layering
+    /// things like gzip or TLS, which require both read and write access to the
+    /// underlying object.
+    ///
+    /// If you want to work more directly with the streams and sink, consider
+    /// calling `split` on the `Framed` returned by this method, which will
+    /// break them into separate objects, allowing them to interact more easily.
+    #[deprecated(since = "0.1.7", note = "Use tokio_codec::Decoder::framed instead")]
+    #[allow(deprecated)]
+    fn framed<T: Encoder + Decoder>(self, codec: T) -> Framed<Self, T>
+        where Self: AsyncWrite + Sized,
+    {
+        framed::framed(self, codec)
+    }
+
+    /// Helper method for splitting this read/write object into two halves.
+    ///
+    /// The two halves returned implement the `Read` and `Write` traits,
+    /// respectively.
+    fn split(self) -> (ReadHalf<Self>, WriteHalf<Self>)
+        where Self: AsyncWrite + Sized,
+    {
+        split::split(self)
+    }
+}
+
+impl<T: ?Sized + AsyncRead> AsyncRead for Box<T> {
+    unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
+        (**self).prepare_uninitialized_buffer(buf)
+    }
+}
+
+impl<'a, T: ?Sized + AsyncRead> AsyncRead for &'a mut T {
+    unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
+        (**self).prepare_uninitialized_buffer(buf)
+    }
+}
+
+impl<'a> AsyncRead for &'a [u8] {
+    unsafe fn prepare_uninitialized_buffer(&self, _buf: &mut [u8]) -> bool {
+        false
+    }
+}