Function ParseTomlFile

Common/ParameterFileParser/itkParameterFileParser.cxx:354–427

Parses the specified TOML file, and returns its key-value pairs as an elastix ParameterMap.

// Parses the specified TOML file, and returns its key-value pairs as an elastix ParameterMap.
auto
ParseTomlFile(const std::string & fileName)
{
  ParameterFileParser::ParameterMapType parameterMap;

  const auto fileContents = [&fileName] {
    std::ifstream inputFileStream(fileName);
    return std::string(std::istreambuf_iterator<char>(inputFileStream), std::istreambuf_iterator<char>());
  }();

  // Retrieves an elastix parameter value from the specified TOML node.
  const auto getParameterValue = [&fileContents, &fileName](const toml::node & tomlNode) -> std::string {
    // When the TOML node holds a string, just use it as it was produced by the TOML parser. (The TOML parser removes
    // surrounding double-quotes from string values.)
    if (const auto * const result = tomlNode.as_string())
    {
      return result->get();
    }

    const auto convertTomlValueToString = [](const auto & tomlValue) {
      return elx::Conversion::ToString(tomlValue.get());
    };

    if (const auto * const result = tomlNode.as_boolean())
    {
      return convertTomlValueToString(*result);
    }
    if (const auto * const result = tomlNode.as_integer())
    {
      return convertTomlValueToString(*result);
    }
    if (const auto * const result = tomlNode.as_floating_point())
    {
      return convertTomlValueToString(*result);
    }

    const toml::source_position sourceRegionBegin = tomlNode.source().begin;
    itkGenericExceptionMacro("Unsupported TOML value type `" << tomlNode.type() << "` in \"" << fileName << "\" "
                                                             << sourceRegionBegin << ", at the following line:\n\""
                                                             << GetLine(fileContents, sourceRegionBegin.line) << "\"");
  };

  try
  {
    for (const auto & [tomlKey, tomlNode] : toml::parse(fileContents))
    {
      const auto parameterName = tomlKey.str();
      auto &     parameterValues = parameterMap[std::string(parameterName)];

      if (const auto tomlArray = tomlNode.as_array())
      {
        // An elastix parameter that may have multiple values.
        for (const toml::node & tomlArrayElement : *tomlArray)
        {
          parameterValues.push_back(getParameterValue(tomlArrayElement));
        }
      }
      else