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