Function out

include/fmt/base.h:1923–1957

// A buffer that writes to an output iterator when flushed.
template <typename OutputIt, typename T, typename Traits = buffer_traits>
class iterator_buffer : public Traits, public buffer<T> {
 private:
  OutputIt out_;
  enum { buffer_size = 256 };
  T data_[buffer_size];

  static FMT_CONSTEXPR void grow(buffer<T>& buf, size_t) {
    if (buf.size() == buffer_size) static_cast<iterator_buffer&>(buf).flush();
  }

  void flush() {
    auto size = this->size();
    this->clear();
    const T* begin = data_;
    const T* end = begin + this->limit(size);
    out_ = copy<T>(begin, end, out_);
  }

 public:
  explicit iterator_buffer(OutputIt out, size_t n = buffer_size)
      : Traits(n), buffer<T>(grow, data_, 0, buffer_size), out_(out) {}
  iterator_buffer(iterator_buffer&& other) noexcept
      : Traits(other),
        buffer<T>(grow, data_, 0, buffer_size),
        out_(other.out_) {}
  ~iterator_buffer() {
    // Don't crash if flush fails during unwinding.
    FMT_TRY { flush(); }
    FMT_CATCH(...) {}
  }

  auto out() -> OutputIt {
    flush();
    return out_;
  }
  auto count() const -> size_t { return Traits::count() + this->size(); }
};