[Mono-list] P/Invoke IntPtr versus byte[]

[Tim Rädisch]

Hi!

Following scenario (it's very absract, because the real programm would be 
needless complicated.

I want to acces the following C-methode by DllImport.

void multiDimArrayTest( const void* array ) {
 int i;
 unsigned char *mdarray = (unsigned char*)array;

 printf("%i %i\n", mdarray, array );

 printf ("size of array[x]: %i\n", sizeof(mdarray[0]) ) ;
 for( i=0; i<64*64*3; i++){
   if( mdarray[i] != 0 )
     printf( "==> array(%i) = %i\n",i, mdarray[i] );
 }
}


In C# I want to access the method with the following array
    byte[]  mdArray = new byte[64*64*3];
    mdArray[1982] = 1;
Every element is 0, except 1982.


Because it is a "const void*" I used the following DllImport statement
  [ DllImport(lib) ]
  static extern void multiDimArrayTest( byte[] elems );
and this methode call
  multiDimArrayTest( GCHandle.Alloc( mdArray, 
GCHandleType.Pinned).AddrOfPinnedObject() );

The output is:
size of array[x]: 1
==> array(0) = 120
==> array(1) = 207
==> array(2) = 4
==> array(3) = 8
==> array(13) = 48
==> array(1998) = 1
Except of 5 elements all are correct. But I don't know why elements 0,1,2,3 
and 13 are wrong.


If I use the following import and call
  [ DllImport(lib) ]
  static extern void multiDimArrayTest( byte[] elems );

  multiDimArrayTest( mdArray );
the output is
size of array[x]: 1
==> array(1982) = 1

and this one is correct.


But I don't want to hard code the type, because it is not ever a byte-array. 
Yes that is possible, it is C :D (not my C)



So, can someone explain me why IntPtr fails, and if there is another 
alternative?


Tim