Type Indicators

After the table of Property Identifiers/Offset Pairs comes the actual properties. Each property is stored as a DWORD type, followed by the data value.

Type indicators and their associated values are described in the PROPVARIANT structure reference page.

All Type/Value pairs must begin on a 32-bit boundary. Thus, values may be followed with null bytes to align the subsequent pair on a 32-bit boundary. Given a count of bytes, the following code will calculate how many bytes are needed to align on a 32-bit boundary:

cbAdd = (((cbCurrent + 3) >> 2) << 2) - cbCurrent ;

Within a vector of values, each repetition of a simple scalar value smaller than 32 bits must align with its natural alignment rather than with a 32-bit alignment. In practice, this is only significant for types VT_UI1, VTUI2, VT_I2, and VT_BOOL (which have one- or two-byte natural alignment). All other types have four-byte natural alignment. Some types (VT_R8, etc.) actually have 8-byte natural alignment, but are stored as if they have 4-byte alignment. Therefore, a property value with type indicator VT_I2 | VT_VECTOR would be:

    A DWORD element count, followed by

    A sequence of packed two-byte integers with no padding between them.

Note that any 32-bit counts or property types that are stored as a part of a vector property element must also be 32-bit aligned.

A property value of type identifier VT_LPSTR | VT_VECTOR would be:

    A DWORD element count (DWORD cElems), followed by

    A sequence of strings (char rgch[]), each of which is preceded by a length count DWORD and may be followed by null padding to round to a 32-bit boundary.