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 12namespace IPC { 13namespace 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. 27class 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_ 111