Make PacketReader/PacketWriter interfaces async-only.

blimp/net/blimp_message_pump.h

 // Copyright 2015 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 BLIMP_NET_BLIMP_MESSAGE_PUMP_H_
 #define BLIMP_NET_BLIMP_MESSAGE_PUMP_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "blimp/net/blimp_net_export.h"
 #include "net/base/completion_callback.h"
 
 namespace net {
 class GrowableIOBuffer;
 }
 
 namespace blimp {
 
 class BlimpMessageProcessor;
 class ConnectionErrorObserver;
 class PacketReader;
 
 // Reads and deserializes incoming packets from |reader_|, and forwards parsed
 // BlimpMessages to |processor_|. When |processor_| is ready to take the next
 // message, the BlimpMessagePump reads the next packet.
 class BLIMP_NET_EXPORT BlimpMessagePump {
  public:
-  // Caller ensures |reader| outlive this object.
+  // Caller ensures that |reader| outlives this object.
   explicit BlimpMessagePump(PacketReader* reader);
 
   ~BlimpMessagePump();
 
-  // Sets the processor which will take blimp messages.
-  // Can be set multiple times, but previously set processors are discarded.
+  // Sets the processor which will take BlimpMessages. Can only be set once.
   // Caller retains the ownership of |processor|.
   void SetMessageProcessor(BlimpMessageProcessor* processor);
 
   void set_error_observer(ConnectionErrorObserver* observer) {
     error_observer_ = observer;
   }
 
  private:
   // Read next packet from |reader_|.
   void ReadNextPacket();
 
   // Callback when next packet is ready in |buffer_|.
   void OnReadPacketComplete(int result);
 
-  // Callback when |processor_| finishes processing a blimp message.
+  // Callback when |processor_| finishes processing a BlimpMessage.
   void OnProcessMessageComplete(int result);
 
   PacketReader* reader_;
   ConnectionErrorObserver* error_observer_;
   BlimpMessageProcessor* processor_;
   scoped_refptr<net::GrowableIOBuffer> buffer_;
-  net::CancelableCompletionCallback read_packet_callback_;
+
+  // Cancelled in the event that the connection is destroyed (along with
+  // |this|) while a inflight callback is held by |processor_|.
   net::CancelableCompletionCallback process_msg_callback_;
 
+  // Cancelled to guard against |this| being called back from a completed read
+  // operation.
+  net::CancelableCompletionCallback read_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(BlimpMessagePump);
 };
 
 }  // namespace blimp
 
 #endif  // BLIMP_NET_BLIMP_MESSAGE_PUMP_H_