1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef IPC_IPC_CHANNEL_READER_H_
6#define IPC_IPC_CHANNEL_READER_H_
7
8#include "base/basictypes.h"
9#include "ipc/ipc_channel.h"
10
11namespace IPC {
12namespace internal {
13
14// This class provides common pipe reading functionality for the
15// platform-specific IPC channel implementations.
16//
17// It does the common input buffer management and message dispatch, while the
18// platform-specific parts provide the pipe management through a virtual
19// interface implemented on a per-platform basis.
20//
21// Note that there is no "writer" corresponding to this because the code for
22// writing to the channel is much simpler and has very little common
23// functionality that would benefit from being factored out. If we add
24// something like that in the future, it would be more appropriate to add it
25// here (and rename appropriately) rather than writing a different class.
26class ChannelReader {
27 public:
28  explicit ChannelReader(Listener* listener);
29  virtual ~ChannelReader();
30
31  void set_listener(Listener* listener) { listener_ = listener; }
32
33  // Call to process messages received from the IPC connection and dispatch
34  // them. Returns false on channel error. True indicates that everything
35  // succeeded, although there may not have been any messages processed.
36  bool ProcessIncomingMessages();
37
38  // Handles asynchronously read data.
39  //
40  // Optionally call this after returning READ_PENDING from ReadData to
41  // indicate that buffer was filled with the given number of bytes of
42  // data. See ReadData for more.
43  bool AsyncReadComplete(int bytes_read);
44
45  // Returns true if the given message is internal to the IPC implementation,
46  // like the "hello" message sent on channel set-up.
47  bool IsInternalMessage(const Message& m) const;
48
49  // Returns true if the given message is an Hello message
50  // sent on channel set-up.
51  bool IsHelloMessage(const Message& m) const;
52
53 protected:
54  enum ReadState { READ_SUCCEEDED, READ_FAILED, READ_PENDING };
55
56  Listener* listener() const { return listener_; }
57
58  // Populates the given buffer with data from the pipe.
59  //
60  // Returns the state of the read. On READ_SUCCESS, the number of bytes
61  // read will be placed into |*bytes_read| (which can be less than the
62  // buffer size). On READ_FAILED, the channel will be closed.
63  //
64  // If the return value is READ_PENDING, it means that there was no data
65  // ready for reading. The implementation is then responsible for either
66  // calling AsyncReadComplete with the number of bytes read into the
67  // buffer, or ProcessIncomingMessages to try the read again (depending
68  // on whether the platform's async I/O is "try again" or "write
69  // asynchronously into your buffer").
70  virtual ReadState ReadData(char* buffer, int buffer_len, int* bytes_read) = 0;
71
72  // Loads the required file desciptors into the given message. Returns true
73  // on success. False means a fatal channel error.
74  //
75  // This will read from the input_fds_ and read more handles from the FD
76  // pipe if necessary.
77  virtual bool WillDispatchInputMessage(Message* msg) = 0;
78
79  // Performs post-dispatch checks. Called when all input buffers are empty,
80  // though there could be more data ready to be read from the OS.
81  virtual bool DidEmptyInputBuffers() = 0;
82
83  // Handles internal messages, like the hello message sent on channel startup.
84  virtual void HandleInternalMessage(const Message& msg) = 0;
85
86 private:
87  // Takes the given data received from the IPC channel and dispatches any
88  // fully completed messages.
89  //
90  // Returns true on success. False means channel error.
91  bool DispatchInputData(const char* input_data, int input_data_len);
92
93  Listener* listener_;
94
95  // We read from the pipe into this buffer. Managed by DispatchInputData, do
96  // not access directly outside that function.
97  char input_buf_[Channel::kReadBufferSize];
98
99  // Large messages that span multiple pipe buffers, get built-up using
100  // this buffer.
101  std::string input_overflow_buf_;
102
103  DISALLOW_COPY_AND_ASSIGN(ChannelReader);
104};
105
106}  // namespace internal
107}  // namespace IPC
108
109#endif  // IPC_IPC_CHANNEL_READER_H_
110