subscription.h

// Copyright 2009-2018 Toby Schneider (http://gobysoft.org/index.wt/people/toby)
//                     GobySoft, LLC (2013-)
//                     Massachusetts Institute of Technology (2007-2014)
//                     Community contributors (see AUTHORS file)
//
//
// This file is part of the Goby Underwater Autonomy Project Libraries
// ("The Goby Libraries").
//
// The Goby Libraries are free software: you can redistribute them and/or modify
// them under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 2.1 of the License, or
// (at your option) any later version.
//
// The Goby Libraries are distributed in the hope that they will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with Goby.  If not, see <http://www.gnu.org/licenses/>.

#ifndef SUBSCRIPTION20110412H
#define SUBSCRIPTION20110412H

#include <boost/function.hpp>
#include <boost/shared_ptr.hpp>
#include <google/protobuf/descriptor.h>
#include <google/protobuf/dynamic_message.h>

namespace goby
{
namespace pb
{
// forms a non-template base for the Subscription class, allowing us
// use a common pointer type.
class SubscriptionBase
{
  public:
    virtual void post(const std::string& body) = 0;
    virtual const google::protobuf::Message& newest() const = 0;
    virtual const std::string& type_name() const = 0;
    virtual const std::string& group() const = 0;
    virtual bool has_valid_handler() const = 0;
};

// forms the concept of a subscription to a given Google Protocol Buffers
// type ProtoBufMessage
// An instantiation of this is created for each call to ApplicationBase::subscribe()
template <typename ProtoBufMessage> class Subscription : public SubscriptionBase
{
  public:
    typedef boost::function<void(const ProtoBufMessage&)> HandlerType;

    Subscription(HandlerType& handler, const std::string& type_name, const std::string& group = "")
        : handler_(handler), type_name_(type_name), group_(group)
    {
    }

    // handle an incoming message (serialized using the google::protobuf
    // library calls)
    void post(const std::string& body)
    {
        newest_msg_.ParseFromString(body);
        if (handler_)
            handler_(newest_msg_);
    }

    // getters
    const google::protobuf::Message& newest() const { return newest_msg_; }
    const std::string& type_name() const { return type_name_; }
    const std::string& group() const { return group_; }
    bool has_valid_handler() const { return handler_; }

  private:
    HandlerType handler_;
    ProtoBufMessage newest_msg_;
    const std::string type_name_;
    const std::string group_;
};
} // namespace pb
} // namespace goby

#endif