Support load and save for classdef objects in MAT-files (bug #45833).

* libinterp/corefcn/load-save.cc (load_save_system::load): Update unwind_action
to include "clear_subsystem_handler".
(load_save_system::load_vars): Move unwind_action from load_vars to load.
(load_save_system::save_vars): Update unwind_action to include
"clear_subsystem_handler". Add new block to write MAT-file subsystem data after
all variables are saved.
* libinterp/corefcn/ls-mat5.cc (read_mat5_binary_file_header): Read subsystem
data from MAT-files into "subsystem_handler" object.
(read_mat5_binary_element): Read classdef objects as case
MAT_FILE_WORKSPACE_CLASS.
(save_mat5_element_length): Update to return element length for classdef
objects.
(save_mat5_binary_element): Update to save classdef objects to file stream.

* test/classdef-load-save/classdef-load-save-v6.tst,
test/classdef-load-save/classdef-load-save-v7.tst: New tests for load and save
with MAT-files in "-v6" and "-v7" file format.
* test/classdef-load-save/classdef-load-save-text.tst: Rename file.
* test/classdef-load-save/module.mk: Include new test files in build system.

Author: Nithin Lakshmisha

libinterp/corefcn/load-save.cc

@@ -393,9 +393,6 @@ load_save_system::load_vars (std::istream& stream,
 
   octave_idx_type count = 0;
 
-  octave::unwind_action
-  clear_obj_cache ([this] () { clear_mcos_object_cache (); });
-
   for (;;)
     {
       bool global = false;
@@ -684,8 +681,14 @@ load_save_system::save_vars (const string_vector& argv, int argv_idx,
   if (write_header_info)
     write_header (os, fmt);
 
+  create_subsystem_handler ();  // for MAT file formats
+
   octave::unwind_action
-  clear_obj_cache ([this] () { clear_mcos_object_cache (); });
+  clear_obj_cache ([this] ()
+    {
+      clear_mcos_object_cache ();
+      clear_subsystem_handler ();
+    });
 
   if (argv_idx == argc)
     {
@@ -735,6 +738,62 @@ load_save_system::save_vars (const string_vector& argv, int argv_idx,
             warning ("save: no such variable '%s'", argv[i].c_str ());
         }
     }
+
+  // write subsystem data
+  if (fmt.type() == MAT5_BINARY || fmt.type() == MAT7_BINARY)  // any other formats?
+    {
+      subsystem_handler *sh = get_subsystem_handler ();
+      sh->serialize_to_cell_array ();
+      // serialized data needs to be saved first to calculate nbytes during save
+
+      if (sh->has_serialized_data ())
+        {
+          // create new output stream for subsystem data
+          std::ostringstream subsys_stream;
+
+          const char *header;
+          if (mach_info::words_big_endian ())
+            header = "\x01\x00\x4d\x49\x00\x00\x00\x00";
+          else
+            header = "\x00\x01\x49\x4d\x00\x00\x00\x00";
+          subsys_stream.write (header, 8);
+
+          // create FileWrapper__ object to register as MAT_FILE_WORKSPACE_CLASS
+          octave::cdef_manager& cdm = octave::__get_cdef_manager__ ();
+          octave::cdef_class filewrapper_class
+            = cdm.make_class ("FileWrapper__", std::list<octave::cdef_class> ());
+          octave_value filewrapper_obj
+            = filewrapper_class.construct (octave_value_list (), true);
+
+          octave_scalar_map subsys_map;
+          subsys_map.assign ("MCOS", filewrapper_obj);
+          // TODO: include other type systems "java" and "handle"
+
+          std::string help;
+          do_save (subsys_stream, subsys_map, "", help, false, MAT5_BINARY,
+                   save_as_floats);
+          // don't use zlib compression on subsys_stream
+
+          // convert stream to uint8NDArray
+          // FIXME: How to optimize?
+          const std::string& stream_data = subsys_stream.str();
+          octave_idx_type data_size = stream_data.size ();
+          uint8NDArray subsys_data (dim_vector (1, data_size));
+          std::memcpy (subsys_data.rwdata(), stream_data.data(), data_size);
+
+          // save the uint8NDArray to original stream without variable name
+          octave_value subsys_value (subsys_data);
+          std::streampos subsys_offset = os.tellp ();
+          do_save (os, subsys_value, "", help, false, fmt, save_as_floats);
+
+          // update subsystem offset in MAT-file header
+          std::streampos current_pos = os.tellp ();
+          os.seekp (116);
+          uint64_t offset_val = static_cast<uint64_t> (subsys_offset);
+          os.write (reinterpret_cast<const char*> (&offset_val), 8);
+          os.seekp (current_pos);
+        }
+    }
 }
 
 void
@@ -1198,6 +1257,15 @@ load_save_system::load (const octave_value_list& args, int nargout)
   bool list_only = false;
   bool verbose = false;
 
+  create_subsystem_handler ();  // for MAT file formats
+
+  octave::unwind_action
+  clear_obj_cache ([this] ()
+    {
+      clear_mcos_object_cache ();
+      clear_subsystem_handler ();
+    });
+
   for (; i < argc; i++)
     {
       if (argv[i] == "-text" || argv[i] == "-t")