chore(request-response): remove deprecated items

Related: https://github.com/libp2p/rust-libp2p/issues/3647.

Pull-Request: #3703.

protocols/request-response/src/codec.rs

@@ -0,0 +1,80 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+pub use libp2p_core::ProtocolName;
+
+use async_trait::async_trait;
+use futures::prelude::*;
+use std::io;
+
+/// A `Codec` defines the request and response types
+/// for a request-response [`Behaviour`](crate::Behaviour) protocol or
+/// protocol family and how they are encoded / decoded on an I/O stream.
+#[async_trait]
+pub trait Codec {
+    /// The type of protocol(s) or protocol versions being negotiated.
+    type Protocol: ProtocolName + Send + Clone;
+    /// The type of inbound and outbound requests.
+    type Request: Send;
+    /// The type of inbound and outbound responses.
+    type Response: Send;
+
+    /// Reads a request from the given I/O stream according to the
+    /// negotiated protocol.
+    async fn read_request<T>(
+        &mut self,
+        protocol: &Self::Protocol,
+        io: &mut T,
+    ) -> io::Result<Self::Request>
+    where
+        T: AsyncRead + Unpin + Send;
+
+    /// Reads a response from the given I/O stream according to the
+    /// negotiated protocol.
+    async fn read_response<T>(
+        &mut self,
+        protocol: &Self::Protocol,
+        io: &mut T,
+    ) -> io::Result<Self::Response>
+    where
+        T: AsyncRead + Unpin + Send;
+
+    /// Writes a request to the given I/O stream according to the
+    /// negotiated protocol.
+    async fn write_request<T>(
+        &mut self,
+        protocol: &Self::Protocol,
+        io: &mut T,
+        req: Self::Request,
+    ) -> io::Result<()>
+    where
+        T: AsyncWrite + Unpin + Send;
+
+    /// Writes a response to the given I/O stream according to the
+    /// negotiated protocol.
+    async fn write_response<T>(
+        &mut self,
+        protocol: &Self::Protocol,
+        io: &mut T,
+        res: Self::Response,
+    ) -> io::Result<()>
+    where
+        T: AsyncWrite + Unpin + Send;
+}