PropVariantToDoubleVector function (propvarutil.h)

Extracts a vector of doubles from a PROPVARIANT structure.

Syntax

PSSTDAPI PropVariantToDoubleVector(
  [in]  REFPROPVARIANT propvar,
  [out] DOUBLE         *prgn,
  [in]  ULONG          crgn,
  [out] ULONG          *pcElem
);

Parameters

[in] propvar

Type: REFPROPVARIANT

Reference to a source PROPVARIANT structure.

[out] prgn

Type: DOUBLE*

Points to a buffer containing crgn DOUBLE values. When this function returns, the buffer has been initialized with pcElem double elements extracted from the source PROPVARIANT structure.

[in] crgn

Type: ULONG

Size in elements of the buffer pointed to by prgn.

[out] pcElem

Type: ULONG*

When this function returns, contains the count of double elements extracted from the source PROPVARIANT structure.

Return value

Type: HRESULT

If this function succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

This helper function is used in places where the calling application expects a PROPVARIANT to hold a double vector value with a fixed number of elements.

If the source PROPVARIANT has type VT_VECTOR | VT_R8 or VT_ARRAY | VT_R8, this helper function extracts up to crgn double values and places them into the buffer pointed to by prgn. If the PROPVARIANT contains more elements than will fit into the prgn buffer, this function returns an error and sets pcElem to 0.

Examples

// IPropertyStore *ppropstore;
// Assume variable ppropstore is initialized and valid
PROPVARIANT propvar = {0};
HRESULT hr = ppropstore->GetValue(PKEY_GPS_DestLongitude, &propvar);
if (SUCCEEDED(hr))
{
         // PKEY_GPS_DestLongitude is expected to produce a VT_VECTOR | VT_R8 with three values, or VT_EMPTY
         // PropVariantToDoubleVector will return an error for VT_EMPTY
         DOUBLE rgLongitude[3];
         ULONG cElem;
         hr = PropVariantToDoubleVector(propvar, &rgLongitude, ARRAYSIZE(rgLongitude), &cElem);
         if (SUCCEEDED(hr))
         {
                 if (cElem == ARRAYSIZE(rgLongitude))
                 {
                          // rgLongitude contains 3 doubles representing the degrees, minutes, and seconds of longitude
                 }
                 else
                 {
                          // The first cElem doubles from propvar are stored in the first 3 elements of rgLongitude
         }
         else
         {
                 // propvar either is VT_EMPTY, or contains something other than a vector of 3 doubles
         }
         PropVariantClear(&propvar);
}

Requirements

See also

InitPropVariantFromDoubleVector

PropVariantGetDoubleElem

PropVariantToDouble

PropVariantToDoubleVectorAlloc

VariantToDoubleArray