1//
2// Copyright (C) 2015 The Android Open Source Project
3//
4// Licensed under the Apache License, Version 2.0 (the "License");
5// you may not use this file except in compliance with the License.
6// You may obtain a copy of the License at
7//
8//      http://www.apache.org/licenses/LICENSE-2.0
9//
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15//
16
17#ifndef TRUNKS_BACKGROUND_COMMAND_TRANSCEIVER_H_
18#define TRUNKS_BACKGROUND_COMMAND_TRANSCEIVER_H_
19
20#include "trunks/command_transceiver.h"
21
22#include <string>
23
24#include <base/memory/ref_counted.h>
25#include <base/memory/weak_ptr.h>
26#include <base/sequenced_task_runner.h>
27
28#include "trunks/trunks_export.h"
29
30namespace trunks {
31
32// Sends commands to another CommandTransceiver on a background thread. Response
33// callbacks are called on the original calling thread.
34// Example:
35//   base::Thread background_thread("my thread");
36//   ...
37//   BackgroundCommandTransceiver background_transceiver(
38//       next_transceiver,
39//       background_thread.message_loop_proxy());
40//   ...
41//   background_transceiver.SendCommand(my_command, MyCallback);
42class TRUNKS_EXPORT BackgroundCommandTransceiver : public CommandTransceiver {
43 public:
44  // All commands will be forwarded to |next_transceiver| on |task_runner|,
45  // regardless of whether the synchronous or asynchronous method is used. This
46  // class will hold a reference count to |task_runner|. If |task_runner| is
47  // nullptr, all commands will be forwarded on the current thread. This class
48  // does not take ownership of |next_transceiver|; it must remain valid for
49  // the lifetime of the object.
50  explicit BackgroundCommandTransceiver(
51      CommandTransceiver* next_transceiver,
52      const scoped_refptr<base::SequencedTaskRunner>& task_runner);
53  ~BackgroundCommandTransceiver() override;
54
55  // CommandTranceiver methods.
56  void SendCommand(const std::string& command,
57                   const ResponseCallback& callback) override;
58  std::string SendCommandAndWait(const std::string& command) override;
59
60 private:
61  // Sends a |command| to the |next_transceiver_| and invokes a |callback| with
62  // the command response.
63  void SendCommandTask(const std::string& command,
64                       const ResponseCallback& callback);
65
66  base::WeakPtr<BackgroundCommandTransceiver> GetWeakPtr() {
67    return weak_factory_.GetWeakPtr();
68  }
69
70  CommandTransceiver* next_transceiver_;
71  scoped_refptr<base::SequencedTaskRunner> task_runner_;
72
73  // Declared last so weak pointers are invalidated first on destruction.
74  base::WeakPtrFactory<BackgroundCommandTransceiver> weak_factory_;
75
76  DISALLOW_COPY_AND_ASSIGN(BackgroundCommandTransceiver);
77};
78
79}  // namespace trunks
80
81#endif  // TRUNKS_BACKGROUND_COMMAND_TRANSCEIVER_H_
82