PROPVARIANT  LKP82R

The PROPVARIANT structure is used in most of the methods of IPropertyStorage to define the type tag and the value of a property in a property set. There are five members. The first, the value type tag, and the last, the value of the property, are significant. The middle three are reserved for future use. The PROPVARIANT structure is defined as follows:

Note  The bool member in previous definitions of this structure has been renamed to boolVal, since some compilers now recognize bool as a keyword.

struct PROPVARIANT{ 

    VARTYPE        vt;          // value type tag

    WORD           wReserved1;

    WORD           wReserved2;

    WORD           wReserved3;

    union { 

    // none                     // VT_EMPTY, VT_NULL, VT_ILLEGAL

    unsigned char  bVal;        // VT_UI1

    short          iVal;        // VT_I2

    USHORT         uiVal;       // VT_UI2

    long           lVal;        // VT_I4

    ULONG          ulVal;       // VT_UI4

    LARGE_INTEGER  hVal;        // VT_I8

    ULARGE_INTEGER uhVal;       // VT_UI8

    float          fltVal;      // VT_R4

    double         dblVal;      // VT_R8

    CY             cyVal;       // VT_CY

    DATE           date;        // VT_DATE

    BSTR           bstrVal;     // VT_BSTR 

    VARIANT_BOOL   boolVal;        // VT_BOOL

    SCODE          scode;       // VT_ERROR

    FILETIME       filetime;    // VT_FILETIME

    LPSTR          pszVal;      // VT_LPSTR     // string in the current system Ansi code page

    LPWSTR         pwszVal;     // VT_LPWSTR    // string in Unicode

    CLSID*         puuid;       // VT_CLSID

    CLIPDATA*      pclipdata;   // VT_CF

    BLOB           blob;        // VT_BLOB, VT_BLOBOBJECT

    IStream*       pStream;     // VT_STREAM, VT_STREAMED_OBJECT

    IStorage*      pStorage;    // VT_STORAGE, VT_STORED_OBJECT

    CAUB           caub;         // VT_VECTOR | VT_UI1

    CAI            cai;          // VT_VECTOR | VT_I2

    CAUI           caui;         // VT_VECTOR | VT_UI2

    CAL            cal;          // VT_VECTOR | VT_I4

    CAUL           caul;         // VT_VECTOR | VT_UI4

    CAH            cah;          // VT_VECTOR | VT_I8

    CAUH           cauh;         // VT_VECTOR | VT_UI8

    CAFLT          caflt;        // VT_VECTOR | VT_R4

    CADBL          cadbl;        // VT_VECTOR | VT_R8

    CACY           cacy;         // VT_VECTOR | VT_CY

    CADATE         cadate;       // VT_VECTOR | VT_DATE

    CABSTR         cabstr;       // VT_VECTOR | VT_BSTR

    CABOOL         cabool;       // VT_VECTOR | VT_BOOL

    CASCODE        cascode;      // VT_VECTOR | VT_ERROR

    CALPSTR        calpstr;      // VT_VECTOR | VT_LPSTR

    CALPWSTR       calpwstr;     // VT_VECTOR | VT_LPWSTR

    CAFILETIME     cafiletime;   // VT_VECTOR | VT_FILETIME

    CACLSID        cauuid;       // VT_VECTOR | VT_CLSID

    CACLIPDATA     caclipdata;   // VT_VECTOR | VT_CF

    CAPROPVARIANT  capropvar;    // VT_VECTOR | VT_VARIANT

    }} PROPVARIANT

Remarks

PROPVARIANT is the fundamental data type by which property values are read and written through the IPropertyStorageKFYHMA interface.

The data type PROPVARIANT is related to the data type VARIANT, defined as part of Automation in OLE2 and defined in the Win32 SDK header file oleauto.h. Several definitions are reused from Automation, as follows:

typedef struct  tagCY { 

    unsigned long      Lo;

    long               Hi;

    } CY

typedef CY             CURRENCY;

typedef short          VARIANT_BOOL;

typedef unsigned short VARTYPE;

typedef double         DATE;

typedef OLECHAR*       BSTR;

typedef struct         tagCLIPDATA { 

    ULONG              cbSize;  //Includes sizeof(ulClipFmt)

    long               ulClipFmt;

    BYTE*              pClipData;

    } CLIPDATA

In addition, several new data types that define counted arrays of other data types are required. The data types of all counted arrays begin with the letters CA (such as CAUB) and have an ORed vt value. The counted array structure has the following form (where name is the specific name of the counted array):

#define TYPEDEF_CA(type, name)

    typedef struct tag ## name { \

        ULONG cElems;\

        type *pElems;\

        } name

Clipboard format identifiers, stored with the tag VT_CF, use one of five different representations (identified in the ulClipFmt member of the CLIPDATA structure):

Within a vector of values, each repetition of a value is to be aligned to 32-bit boundaries. The exception to this rule is scalar types which are less than 32 bits:  VT_UI1, VT_12, VT_U12, and VT_BOOL. Vectors of these values are packed.

Therefore, a value with type tag VT_I2 | VT_VECTOR would be a DWORD element count, followed by a sequence of packed 2-byte integers with no padding between them.

However, a value with type tag VT_LPSTR | VT_VECTOR would be a DWORD element count, followed by a sequence of (DWORD cch, char rgch[]) strings, each of which may be followed by null padding to round to a 32-bit boundary.