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Jason Stipes · Guest

I'd like to transmit an arbitrary data structure through a standard COM
interface as a standard type. I need a way to convert the struct to a
SAFEARRAY, Variant or BSTR. Essentially I want to take the block of memory
and put it into one of these data types so that I can directly get the data
out at the other end. So far BSTR has been a failure and using memcpy
hasn't worked. Has anyone done this before?

Thanks,

Jason

BigStew · Guest

A few years ago I wrote a little test app to do just this.
A COM server passes a struct to the client using a VARIANT.
Code cut/paste from Builder 5 project.

// Server code
#include <safearry.h>
////////////////////////////////////////////////////////////////////////////
/
// TTestDCOMImpl

struct numstruct
{
int num1;
int num2;
int num3;
};

STDMETHODIMP TTestDCOMImpl::GetNums(TVariant* Nums)
{
numstruct n;

n.num1 = 101;
n.num2 = 202;
n.num3 = 303;

TSafeArrayDim1 dim(sizeof(numstruct));
TSafeArrayChar1 sa(dim);

for(int i=0; i<sizeof(numstruct); ++i)
sa[i] = ((char*)(&n))[i];
*Nums = sa.Detach();
return S_OK;
}

// Client code
struct numstruct
{
int num1;
int num2;
int num3;
};

void __fastcall TForm1::DisplayNums()
{
TVariant nums = Server->GetNums();
TSafeArrayChar1 sa = LPSAFEARRAY(nums);

numstruct n;
for(int i=0; i<sizeof(numstruct); ++i)
((char*)(&n))[i] = sa[i];
AnsiString s;
s = "Server says ";
s += IntToStr(n.num1);
s += ", ";
s += IntToStr(n.num2);
s += ", ";
s += IntToStr(n.num3);
s += ".";
Label1->Caption = s;
}

HTH

Stew

"Jason Stipes" <jason.stipes (AT) jhuapl (DOT) edu> wrote

Jason Stipes · Guest

Thanks, that did the trick.

-Jason

"BigStew" <Big_Stew (AT) talk21 (DOT) com> wrote