ligier_helper.cpp

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#include "ligier_helper.hpp"

#include <stdexcept>

#include <stdint.h>
#include <cstring>

#include <arpa/inet.h>

/**
 * \author cpellegrino
 */

namespace ligier {

std::size_t prepare_tag(
    char* buffer
  , std::size_t max_size
  , std::string const& tag
) {
  static std::string const header = "_Subscri";
  static std::string const mode = " w ";
  static std::string const trailer = "_Always";

  uint32_t const tagsize = ntohl(3 + tag.size());

  std::size_t const total_size
      = header.size()
      + sizeof(tagsize)
      + 4
      + mode.size()
      + tag.size()
      + trailer.size()
      + 9;

  if (total_size > max_size) {
    throw std::runtime_error("buffer too small");
  }

  std::memset(buffer, '\0', total_size);

  std::memcpy(buffer, header.c_str(), header.size());
  buffer += header.size();
  std::memcpy(buffer, &tagsize, sizeof(tagsize));
  buffer += sizeof(tagsize);
  buffer += 4;
  std::memcpy(buffer, mode.c_str(), mode.size());
  buffer += mode.size();
  std::memcpy(buffer, tag.c_str(), tag.size());
  buffer += tag.size();
  std::memcpy(buffer, trailer.c_str(), trailer.size());

  return total_size;
}

std::size_t read_data_size(char const* const buffer)
{
  uint32_t const& message_size = *static_cast<uint32_t const* const>(
      static_cast<void const* const>(buffer + 8)
  );

  return ntohl(message_size);
}

} // ns ligier