source: src/Fragmentation/Automation/Connection.hpp@ 81c96b6

/*
 * Connection.hpp
 *
 *  Created on: Oct 21, 2011
 *      Author: heber
 */

#ifndef CONNECTION_HPP_
#define CONNECTION_HPP_

// include config.h
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <boost/archive/text_iarchive.hpp>
#include <boost/archive/text_oarchive.hpp>

#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/tuple/tuple.hpp>
#include <iomanip>
#include <string>
#include <sstream>
#include <vector>

#include "CodePatterns/Log.hpp"

/** The Connection class provides serialization primitives on top of a socket.
 * Each message sent using this class consists of:
 * @li An 8-byte header containing the length of the serialized data in
 * hexadecimal.
 * @li The serialized data.
 */
class Connection
{
public:
  /// Constructor.
  Connection(boost::asio::io_service& io_service)
    : socket_(io_service)
  {
  }

  /// Get the underlying socket. Used for making a Connection or for accepting
  /// an incoming Connection.
  boost::asio::ip::tcp::socket& socket()
  {
    return socket_;
  }

  typedef std::vector<boost::asio::const_buffer> buffers_t;

  /** Prepare data for write operation.
   *
   * The dara is prepared in two blocks: header and data.
   *
   * @param t data to place into buffers
   * @param vector of buffers
   * @return true - data placed in buffer, false - some mismatch, data not placed
   */
  template <typename T>
  bool prepare_write(const T& t, buffers_t &buffers)
  {
    // Serialize the data first so we know how large it is.
    std::ostringstream archive_stream;
    boost::archive::text_oarchive archive(archive_stream);
    archive << t;
    outbound_data_ = archive_stream.str();

    // Format the header.
    std::ostringstream header_stream;
    header_stream << std::setw(header_length)
      << std::hex << outbound_data_.size();
    if (!header_stream || header_stream.str().size() != header_length)
      return false;
    outbound_header_ = header_stream.str();

    // Write the serialized data to the socket. We use "gather-write" to send
    // both the header and the data in a single write operation.
    buffers.push_back(boost::asio::buffer(outbound_header_));
    buffers.push_back(boost::asio::buffer(outbound_data_));
    return true;
  }

  /// Asynchronously write a data structure to the socket.
  template <typename T, typename Handler>
  void async_write(const T& t, Handler handler)
  {
    buffers_t buffers;
    if (!prepare_write(t, buffers)) {
      // Something went wrong, inform the caller.
      boost::system::error_code error(boost::asio::error::invalid_argument);
      socket_.get_io_service().post(boost::bind(handler, error));
      return;
    }
    boost::asio::async_write(socket_, buffers, handler);
  }

  /// Synchronously write a data structure to the socket.
  template <typename T>
  void sync_write(const T& t)
  {
    buffers_t buffers;
    if (prepare_write(t, buffers)) {
      boost::asio::write(socket_, buffers);
    } else {
      ELOG(2, "sync_write failed, data could not be placed in buffers.");
    }
  }

  /// Asynchronously read a data structure from the socket.
  template <typename T, typename Handler>
  void async_read(T& t, Handler handler)
  {
    // Issue a read operation to read exactly the number of bytes in a header.
    void (Connection::*f)(
        const boost::system::error_code&,
        T&, boost::tuple<Handler>)
      = &Connection::handle_read_header<T, Handler>;
    boost::asio::async_read(socket_, boost::asio::buffer(inbound_header_),
        boost::bind(f,
          this, boost::asio::placeholders::error, boost::ref(t),
          boost::make_tuple(handler)));
  }

  /// Synchronously read a data structure from the socket.
  template <typename T, typename Handler>
  void sync_read(T& t, Handler handler)
  {
    // Issue a read operation to read exactly the number of bytes in a header.
    void (Connection::*f)(
        const boost::system::error_code&,
        T&, boost::tuple<Handler>)
      = &Connection::handle_read_header<T, Handler>;
    boost::asio::read(socket_, boost::asio::buffer(inbound_header_));
  }

  /// Handle a completed read of a message header. The handler is passed using
  /// a tuple since boost::bind seems to have trouble binding a function object
  /// created using boost::bind as a parameter.
  template <typename T, typename Handler>
  void handle_read_header(const boost::system::error_code& e,
      T& t, boost::tuple<Handler> handler)
  {
    if (e)
    {
      boost::get<0>(handler)(e);
    }
    else
    {
      // Determine the length of the serialized data.
      std::istringstream is(std::string(inbound_header_, header_length));
      std::size_t inbound_data_size = 0;
      if (!(is >> std::hex >> inbound_data_size))
      {
        // Header doesn't seem to be valid. Inform the caller.
        boost::system::error_code error(boost::asio::error::invalid_argument);
        boost::get<0>(handler)(error);
        return;
      }

      // Start an asynchronous call to receive the data.
      inbound_data_.resize(inbound_data_size);
      void (Connection::*f)(
          const boost::system::error_code&,
          T&, boost::tuple<Handler>)
        = &Connection::handle_read_data<T, Handler>;
      boost::asio::async_read(socket_, boost::asio::buffer(inbound_data_),
        boost::bind(f, this,
          boost::asio::placeholders::error, boost::ref(t), handler));
    }
  }

  /// Handle a completed read of message data.
  template <typename T, typename Handler>
  void handle_read_data(const boost::system::error_code& e,
      T& t, boost::tuple<Handler> handler)
  {
    if (e)
    {
      boost::get<0>(handler)(e);
    }
    else
    {
      // Extract the data structure from the data just received.
      try
      {
        std::string archive_data(&inbound_data_[0], inbound_data_.size());
        std::istringstream archive_stream(archive_data);
        boost::archive::text_iarchive archive(archive_stream);
        archive >> t;
      }
      catch (std::exception& e)
      {
        // Unable to decode data.
        boost::system::error_code error(boost::asio::error::invalid_argument);
        boost::get<0>(handler)(error);
        return;
      }

      // Inform caller that data has been received ok.
      boost::get<0>(handler)(e);
    }
  }

private:
  /// The underlying socket.
  boost::asio::ip::tcp::socket socket_;

  /// The size of a fixed length header.
  enum { header_length = 8 };

  /// Holds an outbound header.
  std::string outbound_header_;

  /// Holds the outbound data.
  std::string outbound_data_;

  /// Holds an inbound header.
  char inbound_header_[header_length];

  /// Holds the inbound data.
  std::vector<char> inbound_data_;
};

typedef boost::shared_ptr<Connection> connection_ptr;

#endif /* CONNECTION_HPP_ */