Use ConnectionErrorObserver, not callbacks, for error handling.

blimp/net/blimp_connection.cc

 // 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.
 
 #include "blimp/net/blimp_connection.h"
 
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 14 matching lines @@
 class BlimpMessageSender : public BlimpMessageProcessor {
  public:
   explicit BlimpMessageSender(PacketWriter* writer);
   ~BlimpMessageSender() override;
 
   void set_error_observer(ConnectionErrorObserver* observer) {
     error_observer_ = observer;
   }
 
   // BlimpMessageProcessor implementation.
+  // |callback| receives net::OK on write success, or receives an error code
+  // otherwise.
   void ProcessMessage(std::unique_ptr<BlimpMessage> message,
                       const net::CompletionCallback& callback) override;
 
  private:
   void OnWritePacketComplete(int result);
 
   PacketWriter* writer_;
   ConnectionErrorObserver* error_observer_ = nullptr;
   scoped_refptr<net::IOBuffer> buffer_;
   net::CompletionCallback pending_process_msg_callback_;
@@ skipping 38 matching lines @@
   writer_->WritePacket(
       scoped_refptr<net::DrainableIOBuffer>(
           new net::DrainableIOBuffer(buffer_.get(), message->ByteSize())),
       base::Bind(&BlimpMessageSender::OnWritePacketComplete,
                  weak_factory_.GetWeakPtr()));
 }
 
 void BlimpMessageSender::OnWritePacketComplete(int result) {
   DVLOG(2) << "OnWritePacketComplete, result=" << result;
   DCHECK_NE(net::ERR_IO_PENDING, result);
-  base::ResetAndReturn(&pending_process_msg_callback_).Run(result);
+
+  // Create a stack-local copy of |pending_process_msg_callback_|, in case an
+  // observer deletes |this|.
+  net::CompletionCallback process_callback =
+      base::ResetAndReturn(&pending_process_msg_callback_);
+
   if (result != net::OK) {
     error_observer_->OnConnectionError(result);
   }
+
+  process_callback.Run(result);
 }
 
 BlimpConnection::BlimpConnection(std::unique_ptr<PacketReader> reader,
                                  std::unique_ptr<PacketWriter> writer)
     : reader_(std::move(reader)),
       message_pump_(new BlimpMessagePump(reader_.get())),
       writer_(std::move(writer)),
       outgoing_msg_processor_(new BlimpMessageSender(writer_.get())) {
   DCHECK(writer_);
+  DCHECK(reader_);
 
-  // Observe the connection errors received by any of this connection's network
-  // objects.
   message_pump_->set_error_observer(this);
   outgoing_msg_processor_->set_error_observer(this);
 }
 
 BlimpConnection::BlimpConnection() {}
 
 BlimpConnection::~BlimpConnection() {
   VLOG(1) << "BlimpConnection destroyed.";
 }
 
@@ skipping 18 matching lines @@
 
 void BlimpConnection::OnConnectionError(int error) {
   VLOG(1) << "OnConnectionError, error=" << error;
 
   // Propagate the error to all observers.
   FOR_EACH_OBSERVER(ConnectionErrorObserver, error_observers_,
                     OnConnectionError(error));
 }
 
 }  // namespace blimp