[bug #68091] Inefficient Integer Data Loading from MAT-Files

"Dmitri A. Sergatskov" <[email protected]> Wed, 29 Apr 2026 13:13:57 -0400 (EDT)
Newsgroups	gmane.comp.gnu.octave.bugs
Message-ID	<[email protected]>
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Follow-up Comment #19, bug #68091 (group octave):

I do not think you want to change signature, but you can try something like:

 template <typename T> struct mat5_underlying { using type = T; };
  template <typename T> struct mat5_underlying<octave_int<T>> { using type =
T; };

                                                         
  template <typename storageT, typename T>
  static void
                                                         
  read_mat5_integer_data_storage (std::istream& is, T *m,
                                  octave_idx_type count, bool swap)
                                                         
  {
    if (count <= 0)
                                                         
      return;     

    using underlyingT = typename mat5_underlying<T>::type;
                                                         
    static_assert (sizeof (T) == sizeof (underlyingT));
    static_assert (std::is_standard_layout_v<T>);
                                                         

                                                         
    std::streamsize n_bytes
      = sizeof (storageT) * static_cast<std::streamsize> (count);
                                                         
                  
    if constexpr (std::is_same_v<storageT, underlyingT>)
                                                         
      {
        auto *raw = reinterpret_cast<storageT *> (m);
                                                         
        is.read (reinterpret_cast<char *> (raw), n_bytes);
        if (swap)
                                                         
          swap_bytes<sizeof (storageT)> (raw, count);
      }
                                                         
    else          
      {
        OCTAVE_LOCAL_BUFFER (storageT, ptr, count);
        is.read (reinterpret_cast<char *> (ptr), n_bytes);
                                                         
        if (swap)
          swap_bytes<sizeof (storageT)> (ptr, count);
                                                         
        for (octave_idx_type i = 0; i < count; i++)
                                                         
          m[i] = ptr[i];
      }
                                                         
  }               


(I have not even tried to compile it.)

Dmitri.
-- 



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