sizeof VARIANT data in C++

Perhaps another expert will offer another opinion, but I believe MS left this type of function out of the VariantXXX methods because the OS is responsible for the memory of the various members...  By that I mean, to allocate a bstr, your supposed to use the SysAllocString, to allocate a safe array, you must use the SafeArrayCreate and so on.

You may get a break and have somebody know of an existing method for doing this.

This sounds pretty plausible, unfortunately.

Ok, let me see if I understand - essentially I'll need to write a method that determines the type from VARTYPE vt, then explicitly calls sizeof for the appropriate type. I've already done this, and it looks something like:

int SizeofVariantData( const _variant_t&  var )
{
    switch( var.vt )
    {
      case VT_EMPTY:
      {
            return 0;
            break;
      }
      case VT_I2:
      {
            return( sizeof( V_I2( &var ) ) );
            break;
      }
      case VT_I4:
      {
            return( sizeof( V_I4( &var ) ) );
            break;
      }
      case VT_R4:
      {
            return( sizeof( (double)V_R4( &var ) ) );
            break;
      }
      case VT_R8:
      {
            return( sizeof( V_R8(&var) ) );
            break;
      }
      case VT_CY:
      {
            return( sizeof( double ) );
            break;
      }
      case VT_DATE:
      {
            return 8;
            break;
      }
      case VT_BSTR:
      {
            return( _bstr_t( V_BSTR( &var ) ).length() );
            break;
      }
      case VT_BOOL:
      {
            return( sizeof( V_BOOL( &var ) ) );
            break;
      }
      case VT_UI1:
      {
            return( sizeof( (unsigned short)V_UI1( &var ) ) );
            break;
      }
      case VT_DECIMAL:
      {
            return( sizeof( double ) );
            break;
      }
      default:
      {
            ATLTRACE( _T("TYPE NOT RECOGNIZED") );
            ATLASSERT( FALSE );
            return -1;
      }
    }
}

I really wish I could find a more general approach - this relies on my knowledge of data type sizes, which I don't necessarily have.

Or am I way off?

1. sorry, i don't read you Q attentionally, and lost
word "encapsulated data".
2. you solution is good: in some places can write shorter:
case VT_ERROR: return sizeof(SCODE); but it is not
  important.
3. No in C++(or i don't know) general metod to find
  sizeof of struct's member in such case.
  I test in all my books and find nothing!
Best regards, Alex

OK, thanks for all the effort!