New undocumented mat-file format!!!!

[David Bateman]

While struggling to reverse engineer matlab's undocumented function
handle saving/loading code, I noticed the statement below in matlab's
release notes

<quote>
New MAT-File Format Based on HDF5

In Version 7.3 (R2006b), you can save MAT-files in a format based on
HDF5. Unlike earlier MAT-file formats, the HDF5-based format is capable
of saving variables that occupy more than 2 GB of storage, including
large arrays created on 64-bit systems.

To save a MAT-file in the HDF5-based format, use the -v7.3 option to the
MATLAB save function or the "w7.3" mode argument to the C or Fortran
matOpen function. The default MAT-file format is the same as that in
Version 7.2 (R2006a).
</quote>

This certainly going to turn around and bite us in the future, though as
its not the default format at the moment we should be ok for a little
long. We'll certainly be incompatible with their HDF5 format, though at
this point I can't find any documentation on exactly what this format is.

In any case this is just a heads up of an up coming issue.

D.