PropVariantToUInt64 function (propvarutil.h)

Extracts a UInt64 value from a PROPVARIANT structure. If no value can be extracted, then a default value is assigned.

Syntax

PSSTDAPI PropVariantToUInt64(
  [in]  REFPROPVARIANT propvarIn,
  [out] ULONGLONG      *pullRet
);

Parameters

[in] propvarIn

Type: REFPROPVARIANT

Reference to a source PROPVARIANT structure.

[out] pullRet

Type: ULONGLONG*

When this function returns, contains the extracted property value if one exists; otherwise, 0.

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 ULONGLONG value. For instance, an application obtaining values from a property store can use this to safely extract the ULONGLONG value for UInt64 properties.

If the source PROPVARIANT has type VT_UI8, this helper function extracts the ULONGLONG value. Otherwise, it attempts to convert the value in the PROPVARIANT structure into a ULONGLONG. If a conversion is not possible, PropVariantToUInt64 will return a failure code and set pullRet to 0. See PropVariantChangeType for a list of possible conversions. Of note, VT_EMPTY is successfully converted to 0.

Examples

The following example, to be included as part of a larger program, demonstrates how to use PropVariantToUInt64 to access a ULONGLONG value in a PROPVARIANT.

// IPropertyStore *ppropstore;

// Assume variable ppropstore is initialized and valid

PROPVARIANT propvar = {0};

HRESULT hr = ppropstore->GetValue(PKEY_Size, &propvar);

if (SUCCEEDED(hr))

{

     // PKEY_Size is expected to produce a VT_UI8 or VT_EMPTY value.

     // PropVariantToUInt64 will convert VT_EMPTY to 0.

     ULONGLONG ullSize;

     hr = PropVariantToUInt64(propvar, &ullSize);

     if (SUCCEEDED(hr))

     {

             // ullSize is now valid

     }

     else

     {

             // ullSize is always 0

     }

     PropVariantClear(&propvar);

}

Requirements

See also

InitPropVariantFromUInt64

PropVariantChangeType

PropVariantToUInt64Vector

VariantToUInt64