ProtocolMessage.h

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// Copyright 2014 GSI, Inc. All rights reserved.
//
//
//
#ifndef __DDS__ProtocolMessage__
#define __DDS__ProtocolMessage__
// DDS
#include "def.h"
// STD
#include <cstring>
#include <memory>
// BOOST
#include <boost/crc.hpp>

namespace dds
{
    namespace protocol_api
    {
        // a very simple protocol
        // |>>>>>>>>> HEADER <<<<|>>>>>>>>>>>>>>>> DATA <<<<<<<<<<<<<<<<<<|
        //
        // HEADER:
        // - HEADER CHECKSUM (2 bytes): uint16_t
        // - CMD (2 bytes): uint16_t
        // - LEN (4 bytes): uint32_t
        // - SENDER ID (8 bytes): uint64_t
        //
        // DATA
        // DATA BLOCK (size of LEN) unsigned char
        //
        //----------------------------------------------------------------------
        struct SMessageHeader
        {
            SMessageHeader()
                : m_crc(0)
                , m_cmd(0)
                , m_len(0)
                , m_ID(0)
            {
            }

            bool isValid() const
            {
                return (getChecksum() == m_crc);
            }
            uint16_t getChecksum() const
            {
                // Calculate header's checksum.
                // In order to do that, we of course should exclude m_crc from the calculation.
                unsigned char const* buf = reinterpret_cast<unsigned char const*>(this);
                boost::crc_16_type crc16;
                crc16.process_bytes(buf + sizeof(uint16_t), sizeof(SMessageHeader) - sizeof(uint16_t));

                return crc16.checksum();
            }

            void clear()
            {
                m_cmd = 0;
                m_len = 0;
            };

            // !!! IMPORTANT. The checksum member should be always on the top of the member's list !!!
            // we exclude it from checksum calculations.
            uint16_t m_crc;
            uint16_t m_cmd;
            uint32_t m_len;
            uint64_t m_ID;
        };

        //----------------------------------------------------------------------

        class CProtocolMessage
        {
          public:
            typedef dds::misc::BYTEVector_t dataContainer_t;
            typedef dataContainer_t::value_type data_t;
            typedef std::shared_ptr<CProtocolMessage> protocolMessagePtr_t;

            enum
            {
                cmd_sign_length = 2
            };
            enum
            {
                header_length = sizeof(SMessageHeader)
            };
            /*  enum
              {
                  max_body_length = 512
              };*/

          public:
            CProtocolMessage();

            CProtocolMessage(uint16_t _cmd, const dds::misc::BYTEVector_t& _data, uint64_t _ID);

          public:
            void encode(uint16_t _cmd, const dds::misc::BYTEVector_t& _data, uint64_t _ID)
            {
                _encode_message(_cmd, _data, _ID);
            }

            void clear();
            void resize(size_t _size); // FIXME: Used in tests to allocate memory for m_data.
            const data_t* data() const;
            data_t* data();
            size_t length() const;
            const data_t* body() const;
            data_t* body();
            size_t body_length() const;
            bool decode_header();
            const SMessageHeader& header() const;
            std::string toString() const;
            dataContainer_t bodyToContainer() const
            {
                dataContainer_t buf(body(), body() + body_length());
                return buf;
            }

          private:
            void _encode_message(uint16_t _cmd, const dataContainer_t& _data, uint64_t _ID);

          private:
            dataContainer_t m_data; 
            SMessageHeader m_header;
        };
    } // namespace protocol_api
} // namespace dds

#endif /* defined(__DDS__ProtocolMessage__) */