Function tryDecode

CesiumGltfReader/src/decodeDataUrls.cpp:51–98

};

std::optional<DecodeResult> tryDecode(const std::string& uri) {
  constexpr std::string_view dataPrefix = "data:";
  constexpr size_t dataPrefixLength = dataPrefix.size();

  constexpr std::string_view base64Indicator = ";base64";
  constexpr size_t base64IndicatorLength = base64Indicator.size();

  if (uri.substr(0, dataPrefixLength) != dataPrefix) {
    return std::nullopt;
  }

  const size_t dataDelimeter = uri.find(',', dataPrefixLength);
  if (dataDelimeter == std::string::npos) {
    return std::nullopt;
  }

  bool isBase64Encoded = false;

  DecodeResult result;

  result.mimeType =
      uri.substr(dataPrefixLength, dataDelimeter - dataPrefixLength);
  if (result.mimeType.size() >= base64IndicatorLength &&
      result.mimeType.substr(
          result.mimeType.size() - base64IndicatorLength,
          base64IndicatorLength) == base64Indicator) {
    isBase64Encoded = true;
    result.mimeType = result.mimeType.substr(
        0,
        result.mimeType.size() - base64IndicatorLength);
  }

  const std::span<const std::byte> data(
      reinterpret_cast<const std::byte*>(uri.data()) + dataDelimeter + 1,
      uri.size() - dataDelimeter - 1);

  if (isBase64Encoded) {
    result.data = decodeBase64(data);
    if (result.data.empty() && !data.empty()) {
      // base64 decode failed.
      return std::nullopt;
    }
  } else {
    result.data = std::vector<std::byte>(data.begin(), data.end());
  }

  return result;
}
} // namespace

void decodeDataUrls(