Resolving Variants





0/5 (0 vote)
Jul 17, 2001

66608

2
Dereferincing and resolving Variants and IDispatch
Introduction
I have created a recursive function to dereference a passed VARIANT
([in]) and
to resolve IDispatch
if the contained variable in the passed VARIANT
is of type VT_DISPATCH
.
I could use VariantCopy
and/or VariantCopyInd
, but I wanted to avoid copying arrays or other types that are not expected.
Please take a look at the my function ResolveVariant()
(sorry if it is long) and let me know if you find any problems. I have done some testing and I dont see any problems (including ref. counting).
HRESULT SomeClass::get_Item(VARIANT Index, VARIANT* pVar) { VARIANT varOut; VariantInit(&varOut); HRESULT hr = ResolveVariant(&Index, &varOut); if (!FAILED( hr ) { switch (varOut.vt) { case VT_BSTR: SomeCodeHere to prepare pVar; break; case VT_I4: SomeCodeHere to prepare pVar; break; default: break; } VariantClear(&varOut); } else return hr; } HRESULT ResolveVariant(VARIANT* pVarIn, VARIANT* pVarOut) { VARIANT* tmpVarIn = pVarIn; ULONG ByRef = 0; while(tmpVarIn->vt == (VT_BYREF | VT_VARIANT) ) tmpVarIn = tmpVarIn->pvarVal; if(tmpVarIn->vt & VT_BYREF) ByRef = VT_BYREF; switch(tmpVarIn->vt) { case (VT_I2): case (VT_BYREF|VT_I2): if(ByRef) { if(!tmpVarIn->piVal) return E_POINTER; pVarOut->iVal = *(tmpVarIn->piVal); } break; case (VT_I4): case (VT_BYREF|VT_I4): if(ByRef) { if(!tmpVarIn->plVal) return E_POINTER; pVarOut->lVal = *(tmpVarIn->plVal); } break; case (VT_BSTR): case (VT_BYREF|VT_BSTR): if(ByRef) { if(!tmpVarIn->pbstrVal) return E_POINTER; if(!*(tmpVarIn->pbstrVal) ) return E_POINTER; pVarOut->bstrVal = *(tmpVarIn->pbstrVal); } break; case (VT_DISPATCH): case (VT_BYREF|VT_DISPATCH): if(ByRef) { if(!tmpVarIn->ppdispVal) return E_POINTER; if(!*(tmpVarIn->ppdispVal) ) return E_POINTER; pVarOut->pdispVal = *(tmpVarIn->ppdispVal); } break; default: return DISP_E_TYPEMISMATCH; } if(ByRef) pVarOut->vt = (tmpVarIn->vt - ByRef); else *pVarOut = *tmpVarIn; if (pVarOut->vt == VT_DISPATCH) { VARIANT varResolved; DISPPARAMS dispParamsNoArgs = {NULL, NULL, 0, 0}; VariantInit(&varResolved); if ( SUCCEEDED pVarOut->pdispVal->Invoke(DISPID_VALUE, IID_NULL, LOCALE_SYSTEM_DEFAULT, DISPATCH_PROPERTYGET | DISPATCH_METHOD, &dispParamsNoArgs, &varResolved, NULL, NULL) ) ) { ResolveVariant(&varResolved, pVarOut); } else return E_FAIL; VariantClear(&varResolved); return S_OK; } else { HRESULT hr; VARIANT retVar; VariantInit(&retVar); hr = VariantCopy(&retVar, pVarOut); *pVarOut = retVar; return hr; } }