Create new class "CastTransport", which encapsulates the message read and write event loops.

extensions/browser/api/cast_channel/cast_transport.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef EXTENSIONS_BROWSER_API_CAST_CHANNEL_CAST_TRANSPORT_H_
+#define EXTENSIONS_BROWSER_API_CAST_CHANNEL_CAST_TRANSPORT_H_
+
+#include <queue>
+#include <string>
+
+#include "base/memory/ref_counted.h"
+#include "base/threading/thread_checker.h"
+#include "extensions/common/api/cast_channel.h"
+#include "net/base/completion_callback.h"
+
+namespace net {
+class DrainableIOBuffer;
+class IPEndPoint;
+class IOBuffer;
+class DrainableIOBuffer;
+class GrowableIOBuffer;
+}  // namespace net
+
+namespace extensions {
+namespace core_api {
+namespace cast_channel {
+class CastMessage;
+struct LastErrors;
+class Logger;
+class MessageFramer;
+
+// TODO(kmarshall): Migrate CastSocket to new interface.
+// Skeletal placeholder for a future implementation of CastSocket.
+// New to this interface are read/write calls that operate on simple buffers.
+// Methods that operate on CastMessage/MessageInfo objects will be removed.
+class CastSocketInterface {
+ public:
+  CastSocketInterface() {}
+  virtual ~CastSocketInterface() {}
+
+  virtual int Write(net::IOBuffer* buffer,
+                    size_t size,
+                    const net::CompletionCallback& callback) = 0;
+  virtual int Read(net::IOBuffer* buf,
+                   int buf_len,
+                   const net::CompletionCallback& callback) = 0;
+  virtual void CloseWithError(ChannelError error) = 0;
+  virtual const net::IPEndPoint& ip_endpoint() const = 0;
+  virtual ChannelAuthType channel_auth() const = 0;
+  virtual int id() const = 0;
+};
+
+// Manager class for reading and writing messages to/from a CastSocket.
+class CastTransport {
+ public:
+  // Object to be informed of incoming messages and errors.
+  class Delegate {
+   public:
+    // An error occurred on the channel. |last_errors| contains the last errors
+    // logged for the channel from the implementation.
+    virtual void OnError(const CastSocketInterface* socket,
+                         ChannelError error_state,
+                         const LastErrors& last_errors) = 0;
+    // A message was received on the channel.
+    virtual void OnMessage(const CastSocketInterface* socket,
+                           const CastMessage& message) = 0;
+
+   protected:
+    virtual ~Delegate() {}
+  };
+
+  CastTransport(CastSocketInterface* socket,
+                Delegate* read_delegate,
+                scoped_refptr<Logger> logger);
+  virtual ~CastTransport();
+
+  // Sends a CastMessage to |socket_|.
+  // |message|: The message to send.
+  // |callback|: Callback to be invoked when the write operation has finished.
+  void SendMessage(const CastMessage& message,
+                   const net::CompletionCallback& callback);
+
+  // Starts reading messages from |socket_|.
+  void StartReadLoop();
+
+  // Internal write states.
+  enum WriteState {
+    WRITE_STATE_NONE,
+    WRITE_STATE_WRITE,
+    WRITE_STATE_WRITE_COMPLETE,
+    WRITE_STATE_DO_CALLBACK,
+    WRITE_STATE_ERROR,
+  };
+
+  // Internal read states.
+  enum ReadState {
+    READ_STATE_NONE,
+    READ_STATE_READ,
+    READ_STATE_READ_COMPLETE,
+    READ_STATE_DO_CALLBACK,
+    READ_STATE_ERROR,
+  };
+
+ private:
+  // Holds a message to be written to the socket. |callback| is invoked when the
+  // message is fully written or an error occurrs.
+  struct WriteRequest {
+    explicit WriteRequest(const std::string& namespace_,
+                          const std::string& payload,
+                          const net::CompletionCallback& callback);
+    ~WriteRequest();
+
+    // Namespace of the serialized message.
+    std::string message_namespace;
+    // Write completion callback, invoked when the operation has completed or
+    // failed.
+    net::CompletionCallback callback;
+    // Buffer with outgoing data.
+    scoped_refptr<net::DrainableIOBuffer> io_buffer;
+  };
+
+  // Terminates all in-flight write callbacks with error code ERR_FAILED.
+  void FlushWriteQueue();
+
+  // Main method that performs write flow state transitions.
+  void OnWriteResult(int result);
+
+  // Each of the below Do* method is executed in the corresponding
+  // write state. For example when write state is WRITE_STATE_WRITE_COMPLETE
+  // DowriteComplete is called, and so on.
+  int DoWrite();
+  int DoWriteComplete(int result);
+  int DoWriteCallback();
+  int DoWriteError(int result);
+
+  // Main method that performs write flow state transitions.
+  void OnReadResult(int result);
+
+  // Each of the below Do* method is executed in the corresponding
+  // write state. For example when write state is READ_STATE_READ_COMPLETE
+  // DoReadComplete is called, and so on.
+  int DoRead();
+  int DoReadComplete(int result);
+  int DoReadCallback();
+  int DoReadError(int result);
+
+  void SetReadState(ReadState read_state);
+  void SetWriteState(WriteState write_state);
+  void SetErrorState(ChannelError error_state);
+
+  // Queue of pending writes. The message at the front of the queue is the one
+  // being written.
+  std::queue<WriteRequest> write_queue_;
+
+  // Buffer used for read operations. Reused for every read.
+  scoped_refptr<net::GrowableIOBuffer> read_buffer_;
+
+  // Constructs and parses the wire representation of message frames.
+  scoped_ptr<MessageFramer> framer_;
+
+  // Last message received on the socket.
+  scoped_ptr<CastMessage> current_message_;
+
+  // Socket used for I/O operations.
+  CastSocketInterface* socket_;

[miu, 2014/09/15 19:08:36]

Should be:

  CastSocketInterface* const socket_;

...since this pointer is injected at construction time, is never changed, and
correct behavior of the implementation requires it never be changed.  Looks like
|read_delegate_| could be const too.

Fun/interesting read: http://gamesfromwithin.com/the-const-nazi

[Kevin M, 2014/09/16 21:23:10]

Done.

[miu, 2014/09/16 21:39:53]

?  Doesn't seem to be in patch set 5.

[Kevin M, 2014/09/16 21:45:59]

Didn't catch that git cl upload failed (oops, bad include order.) OK, now PTAL.

+
+  // Methods for communicating message receipt and error status to client code.
+  Delegate* read_delegate_;
+
+  // Write flow state machine state.
+  WriteState write_state_;
+
+  // Read flow state machine state.
+  ReadState read_state_;
+
+  // Most recent error that occurred during read or write operation, if any.
+  ChannelError error_state_;
+
+  scoped_refptr<Logger> logger_;
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(CastTransport);
+};
+}  // namespace cast_channel
+}  // namespace core_api
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_API_CAST_CHANNEL_CAST_TRANSPORT_H_