Function stringFormat

src/image_int.cpp:12–36

namespace Exiv2::Internal {
std::string stringFormat(const char* format, ...) {
  std::string result;
  std::vector<char> buffer;
  size_t need = std::strlen(format) * 8;  // initial guess
  int rc = -1;

  // vsnprintf writes at most size (2nd parameter) bytes (including \0)
  //           returns the number of bytes required for the formatted string excluding \0
  // the following loop goes through:
  // one iteration (if 'need' was large enough for the for formatted string)
  // or two iterations (after the first call to vsnprintf we know the required length)
  do {
    buffer.resize(need + 1);
    va_list args;            // variable arg list
    va_start(args, format);  // args start after format
    rc = vsnprintf(buffer.data(), buffer.size(), format, args);
    va_end(args);  // free the args
    if (rc > 0)
      need = static_cast<size_t>(rc);
  } while (buffer.size() <= need);

  if (rc > 0)
    result = std::string(buffer.data(), need);
  return result;
}

[[nodiscard]] std::string indent(size_t i) {
  return std::string(2 * i, ' ');