Hello,
I posted this to m.p.d.languages.vb, but was told this is a better
place to ask (and I worded my question poorly there, so I think I
miss-communicated my question).

What I need to do is send a parameter from VB.net to an Unmanaged C dll
call, and that parameter on the C side is a pointer to unsigned char,
and is assumed to be allocated n bytes (which is also a parameter).
VB.net needs to be able to send an empty Byte() that will be filled by
the DLL. I have access to both the C and the VB.net, so can make
changes in all the appropriate places.

I have attempted to do with with a memcpy and byte by byte with pointer
arithmetic, but I get a stack overflow, or an unbalanced stack message.
Here are some relevant code snippets trying to express what it is I am
attempting:

Unmanaged C DLL code:

int _stdcall getBytes(unsigned char* vbBytes, int alloced, int* filled)
{
   int i;
   // Hard code for testing
   unsigned char cBytes[] = {
       0x03, 0x84, 0x44, 0xc1, 0x12, 0x61, 0xb5, 0x4A, 0x21, 0x00,
       0xe0, 0x7f, 0xff, 0x00, 0xcb, 0xa9, 0x33, 0x34, 0x7f, 0x4A,
       0x01, 0x7f, 0xff, 0x00, 0xca, 0x8f, 0x55, 0x7f, 0x39, 0x1c,
       0x4c, 0x23, 0x00, 0xcd, 0x00, 0xaf, 0xc3, 0xc8, 0x00, 0x30,
       0x0c, 0x50, 0x00, 0x10, 0x58, 0x03, 0xff, 0x00, 0x01, 0x30,
       0x03, 0xdc, 0xe4, 0x9f, 0x4b, 0xd2, 0x66, 0x04, 0x64, 0xc2,
       0x1f, 0x00 };

   if(alloced < 62)
       return 1;

/* This won't work either
   for(i = 0; i < alloced; i++)
       *(vbBytes++) = *(cBytes++);
   *filled = i;
*/
   memcpy(vbBytes, cBytes, alloced);
   *filled = alloced;

   return 0;
}

VB.net:
       Private Declare Auto Function getBytes Lib "example.dll" _
           (ByRef bytes As Byte(), ByVal alloced As Integer, ByVal
filled As Integer) As Integer

       Public Sub getState()
           Dim ba(75) As Byte
           Dim filled As Integer
           getBytes(ba, 74, filled)
           For Each b As Byte In ba
               Debug.Print(String.Format("0x{0:x2}", b))
           Next
       End Sub