Function append

include/fmt/base.h:1823–1841

  /// Appends data to the end of the buffer.
  template <typename U>
  FMT_CONSTEXPR20 void append(const U* begin, const U* end) {
    static_assert(std::is_same<T, U>() || std::is_same<U, char>(), "");
    while (begin != end) {
      auto size = size_;
      auto free_cap = capacity_ - size;
      auto count = to_unsigned(end - begin);
      if (free_cap < count) {
        grow_(*this, size + count);
        size = size_;
        free_cap = capacity_ - size;
        count = count < free_cap ? count : free_cap;
      }
      // A loop is faster than memcpy on small sizes.
      T* out = ptr_ + size;
      for (size_t i = 0; i < count; ++i) out[i] = static_cast<T>(begin[i]);
      size_ += count;
      begin += count;
    }
  }

  template <typename Idx> FMT_CONSTEXPR auto operator[](Idx index) -> T& {
    return ptr_[index];