Question

I am a COM object written in ATL that is used from a C++ application, and I want to pass an array of BYTEs between the two. My experience of COM/IDL so far is limited to passing simple types (BSTRs, LONGs, etc.).

Is there a relatively easy way to have the COM object pass an array to the caller? For example, I want to pass a raw image (TIFF) instead of messing with temporary files.

Answer 1

Try passing a safearray variant to the COM Object. Something like this to put a BYTE array inside a safearray variant….

bool ArrayToVariant(CArray<BYTE, BYTE>& array, VARIANT& vtResult) { SAFEARRAY FAR*  psarray; SAFEARRAYBOUND sabounds[1];   sabounds[0].lLbound=0; sabounds[0].cElements = (ULONG)array.GetSize();  long nLbound;  psarray = SafeArrayCreate(VT_UI1, 1, sabounds); if(psarray == NULL)     return false;  for(nLbound = 0; nLbound < (long)sabounds[0].cElements ; nLbound++){     if(FAILED(SafeArrayPutElement(psarray, &nLbound, &array[nLbound]))){         SafeArrayDestroy(psarray);         return false;     } }  VariantFree(vtResult); vtResult.vt = VT_ARRAY|VT_UI1; vtResult.parray = psarray; return true; }