// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef IPC_IPC_CHANNEL_READER_H_
#define IPC_IPC_CHANNEL_READER_H_
#include "base/basictypes.h"
#include "ipc/ipc_channel.h"
namespace IPC {
namespace internal {
// This class provides common pipe reading functionality for the
// platform-specific IPC channel implementations.
//
// It does the common input buffer management and message dispatch, while the
// platform-specific parts provide the pipe management through a virtual
// interface implemented on a per-platform basis.
//
// Note that there is no "writer" corresponding to this because the code for
// writing to the channel is much simpler and has very little common
// functionality that would benefit from being factored out. If we add
// something like that in the future, it would be more appropriate to add it
// here (and rename appropriately) rather than writing a different class.
class ChannelReader {
public:
explicit ChannelReader(Listener* listener);
virtual ~ChannelReader();
void set_listener(Listener* listener) { listener_ = listener; }
// Call to process messages received from the IPC connection and dispatch
// them. Returns false on channel error. True indicates that everything
// succeeded, although there may not have been any messages processed.
bool ProcessIncomingMessages();
// Handles asynchronously read data.
//
// Optionally call this after returning READ_PENDING from ReadData to
// indicate that buffer was filled with the given number of bytes of
// data. See ReadData for more.
bool AsyncReadComplete(int bytes_read);
// Returns true if the given message is internal to the IPC implementation,
// like the "hello" message sent on channel set-up.
bool IsInternalMessage(const Message& m) const;
// Returns true if the given message is an Hello message
// sent on channel set-up.
bool IsHelloMessage(const Message& m) const;
protected:
enum ReadState { READ_SUCCEEDED, READ_FAILED, READ_PENDING };
Listener* listener() const { return listener_; }
// Populates the given buffer with data from the pipe.
//
// Returns the state of the read. On READ_SUCCESS, the number of bytes
// read will be placed into |*bytes_read| (which can be less than the
// buffer size). On READ_FAILED, the channel will be closed.
//
// If the return value is READ_PENDING, it means that there was no data
// ready for reading. The implementation is then responsible for either
// calling AsyncReadComplete with the number of bytes read into the
// buffer, or ProcessIncomingMessages to try the read again (depending
// on whether the platform's async I/O is "try again" or "write
// asynchronously into your buffer").
virtual ReadState ReadData(char* buffer, int buffer_len, int* bytes_read) = 0;
// Loads the required file desciptors into the given message. Returns true
// on success. False means a fatal channel error.
//
// This will read from the input_fds_ and read more handles from the FD
// pipe if necessary.
virtual bool WillDispatchInputMessage(Message* msg) = 0;
// Performs post-dispatch checks. Called when all input buffers are empty,
// though there could be more data ready to be read from the OS.
virtual bool DidEmptyInputBuffers() = 0;
// Handles internal messages, like the hello message sent on channel startup.
virtual void HandleInternalMessage(const Message& msg) = 0;
private:
// Takes the given data received from the IPC channel and dispatches any
// fully completed messages.
//
// Returns true on success. False means channel error.
bool DispatchInputData(const char* input_data, int input_data_len);
Listener* listener_;
// We read from the pipe into this buffer. Managed by DispatchInputData, do
// not access directly outside that function.
char input_buf_[Channel::kReadBufferSize];
// Large messages that span multiple pipe buffers, get built-up using
// this buffer.
std::string input_overflow_buf_;
DISALLOW_COPY_AND_ASSIGN(ChannelReader);
};
} // namespace internal
} // namespace IPC
#endif // IPC_IPC_CHANNEL_READER_H_