ipc/ipc_channel_reader.h

   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
  11 namespace IPC {
  12 namespace 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.
  26 class 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 the "hello" message sent on channel
  46   // set-up.
  47   bool IsHelloMessage(const Message& m) const;
  48
  49  protected:
  50   enum ReadState { READ_SUCCEEDED, READ_FAILED, READ_PENDING };
  51
  52   Listener* listener() const { return listener_; }
  53
  54   // Populates the given buffer with data from the pipe.
  55   //
  56   // Returns the state of the read. On READ_SUCCESS, the number of bytes
  57   // read will be placed into |*bytes_read| (which can be less than the
  58   // buffer size). On READ_FAILED, the channel will be closed.
  59   //
  60   // If the return value is READ_PENDING, it means that there was no data
  61   // ready for reading. The implementation is then responsible for either
  62   // calling AsyncReadComplete with the number of bytes read into the
  63   // buffer, or ProcessIncomingMessages to try the read again (depending
  64   // on whether the platform's async I/O is "try again" or "write
  65   // asynchronously into your buffer").
  66   virtual ReadState ReadData(char* buffer, int buffer_len, int* bytes_read) = 0;
  67
  68   // Loads the required file desciptors into the given message. Returns true
  69   // on success. False means a fatal channel error.
  70   //
  71   // This will read from the input_fds_ and read more handles from the FD
  72   // pipe if necessary.
  73   virtual bool WillDispatchInputMessage(Message* msg) = 0;
  74
  75   // Performs post-dispatch checks. Called when all input buffers are empty,
  76   // though there could be more data ready to be read from the OS.
  77   virtual bool DidEmptyInputBuffers() = 0;
  78
  79   // Handles the first message sent over the pipe which contains setup info.
  80   virtual void HandleHelloMessage(const Message& msg) = 0;
  81
  82  private:
  83   // Takes the given data received from the IPC channel and dispatches any
  84   // fully completed messages.
  85   //
  86   // Returns true on success. False means channel error.
  87   bool DispatchInputData(const char* input_data, int input_data_len);
  88
  89   Listener* listener_;
  90
  91   // We read from the pipe into this buffer. Managed by DispatchInputData, do
  92   // not access directly outside that function.
  93   char input_buf_[Channel::kReadBufferSize];
  94
  95   // Large messages that span multiple pipe buffers, get built-up using
  96   // this buffer.
  97   std::string input_overflow_buf_;
  98
  99   DISALLOW_COPY_AND_ASSIGN(ChannelReader);
 100 };
 101
 102 }  // namespace internal
 103 }  // namespace IPC
 104
 105 #endif  // IPC_IPC_CHANNEL_READER_H_