PROPVARIANT

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 IPropertyStorage 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.

QuickInfo

  Windows NT: Use version 4.0 or later.
  Windows: Use Windows 95 or later. Available as a redistributable for Windows 95.
  Windows CE: Unsupported.
  Header: Declared in objidl.h.