How unpack a charNDArray using pvm library?

[John W. Eaton]

On 28-Feb-2007, Riccardo Corradini wrote:

| DEFUN_DLD(pvm_pkcharMAT,args,, "This function emulates the C function 
pvm_pkbyte of pvm3 library, but packs any char matrixes with any dimensions \n")
| {
| 
| 
| 
|   octave_value_list retval;
|   double nargin = args.length ();
| 
|   if (nargin != 2)
|     {
|       error ("expecting 2 input arguments");
|       return retval;
|     }
| 
|   const charNDArray tarray = args(0).char_array_value();
|   int nitem = tarray.capacity();
|   char *p  = const_cast<char*>( tarray.data() );

I dont' think you should be using const_cast here.  Octave is not
designed for you to be modifying arguments passed to functions.  If
you need to do that, you need to make a copy, and return the copy to
the caller.  To do that, write

  charNDArray tarray = args(0).char_array_value ();
  char *p = tarray.fortran_vec ();

Or, if it is just that 

|     int info2 = pvm_pkbyte (p, nitem, stride);

has the wrong declaration for the first arg (char* instead of const
char*), and it really doesn't ever modify the contents of the vector,
then maybe you should fix the declaration of pvm_pkbyte?

| // Could I use an octave_local_buffer macro if so .. how?
|   charNDArray   oar (dv);
|   if( (n != oar.capacity()) )
|     {
|       error ("errors with dims");
|       return retval;
|     }
| 
|   char *preal   = const_cast<char*>( oar.data() );

Again, I dont' think you want a const_cast here.  Use

  char *preal = oar.fortran_vec ();

|     int info1 = pvm_upkbyte (preal, n, stride);
|   retval(0) = static_cast<int>(info1);

It looks like the type of info1 is already an int, so why do you use a
cast here?

|   return octave_value_list(retval);

The variable retval is already an octave_value_list, so you can just
write

  return retval;

jwe