OpenLCP/protocol/esta/rdm/message.h

/*
  message.h

  Copyright (c) 2021 Kevin Matz (kevin.matz@gmail.com)

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
#pragma once

#include <cstdint>
#include <memory>
#include <vector>

#include "rdm.h"
#include "uid.h"

namespace RDM {

struct Message;                             //!< \cite RDM 6 Message Structure

using MsgPtr = std::shared_ptr<Message>;    //!< Managed RDM Message pointer.

/**
 * @brief \cite RDM 6.2 Packet Format
 *
 * \cite RDM All RDM packets shall use the following message structure, with the exception
 * of the Discovery Unique Branch response message.
 */
struct Message
{
  explicit Message();

  UID destination;        //!< \cite RDM 6.2.4 Destination UID
  UID source;             //!< \cite RDM 6.2.5 Source UID
  uint8_t tn;             //!< \cite RDM 6.2.6 Transaction Number (TN)
  union {
    uint8_t portID;       //!< \cite RDM 6.2.7.1 Port ID for Controller Generated Messages
    uint8_t responseType; //!< \cite RDM 6.2.7.2 Response Type for Responder Generated Messages
  };
  uint8_t messageCount;   //!< \cite RDM 6.2.8 Message Count
  uint16_t subDevice;     //!< \cite RDM 6.2.9 Sub-Device Field

  /// \cite RDM Table 6-4 shows the format of the Message Data Block portion
  /// of the data packet from Table 6-2.
  struct DataBlock {
    uint8_t cc;                             //!< \cite RDM 6.2.10.1 Command Class (CC)
    PID     pid;                            //!< \cite RDM 6.2.10.2 Parameter ID (PID)
    uint8_t pdl() const {return pd.size();} //!< \cite RDM 6.2.10.3 Parameter Data Length (PDL) @return
    std::vector<uint8_t> pd;                //!< \cite RDM 6.2.10.4 Parameter Data (PD)
  } mdb;                                    //!< \cite RDM 6.2.10 Message Data Block (MDB)

  uint16_t checksum() const;    //!< \cite RDM 6.2.11 Checksum

  union {
    uint8_t failure_mode;
    struct {
      bool short_message   : 1; //!< undersized buffer
      bool length_mismatch : 1; //!< message longer than adervertised
      bool checksum_fail   : 1; //!< message did not match checksum
      bool incorrect_sc    : 1; //!< invalid StartCode
      bool incorrect_sub_sc: 1; //!< invalid sub-StartCode
      bool do_not_send     : 1; //!< message does not require transmission
    };
  };

  void read(const std::vector<uint8_t> &buffer);
  void write(std::vector<uint8_t> &buffer) const;
  void nak(uint16_t reason);

private:
  void writeDiscBranch(std::vector<uint8_t> &buffer) const;

public: // templates
  /**
   * @brief Big-Endian Read from std::vector
   * @param buffer
   * @param index
   * @return
   *
   * > \cite RDM 6.1 Byte Ordering
   * > All multi-byte data shall be transmitted in Big-Endian order.
   */
  template<typename T>
  static T readType(const std::vector<uint8_t> &buffer, const size_t index)
  {
    if (buffer.size() < sizeof(T))
      return 0;
    T val = 0;
    auto data = reinterpret_cast<uint8_t*>(&val);
    for (int i = 0; i < sizeof(T); i++)
        data[sizeof(T)-1-i] = buffer[index + i];
    return val;
  }

  /**
   * @brief Big-Endian Write to std::vector
   * @param buffer
   * @param val
   *
   * > \cite RDM 6.1 Byte Ordering
   * > All multi-byte data shall be transmitted in Big-Endian order.
   */
  template<typename T>
  static void writeType(std::vector<uint8_t> &buffer, const T &val)
  {
    auto data = reinterpret_cast<const uint8_t*>(&val);
    for (int i = 0; i < sizeof(T); i++)
      buffer.push_back(data[sizeof(T)-1-i]);
  }

  /**
   * @brief Endian-correct appending of Parameter Data
   * @param val
   */
  template<typename T>
  void appendParameterData(const T &val)
  {
    Message::writeType<T>(mdb.pd, val);
  }

private: // templates
  /**
   * @brief addSum_
   * @param sum
   * @param val
   */
  template<typename T>
  static void addSum_(uint16_t &sum, const T &val)
  {
    uint8_t byte;
    uint16_t carry;
    auto data = reinterpret_cast<const uint8_t*>(&val);
    for (int i = sizeof(T);  --i >= 0; )
    {
      byte = data[i];
      while (byte != 0)
      {
        carry = sum & byte;
        sum = sum ^ byte;
        byte = carry << 1;
      }
    }
  }

}; // struct Message

} // namespace RDM