Binaryworld - GetArrayInfo - Retreive number of dimensions and the SAFEARRAY memory ... [ VB -> Arrays ]

Type SAFEARRAYBOUND
  cElements As Long   ' # of elements in the array dimension
  lLbound   As Long   ' lower bounds of the array dimension
End Type

Type SAFEARRAY
  cDims    As Integer ' Count of dimensions in this array.
  fFeatures As Integer ' Flags used by the SAFEARRAY routines documented
               ' below.
  cbElements As Long   ' Size of an element of the array.
  cLocks   As Long   ' Number of times the array has been
               ' locked without corresponding unlock.
  pvData   As Long   ' Pointer to the data.
  rgsabound(1 To 60) As SAFEARRAYBOUND ' One bound for each dimension.
  ' An array can have max 60 dimensions, only the first cDims items will be
  ' used
  ' note that rgsabound elements are in reverse order,
  ' e.g. for a 2-dimensional
  ' array, rgsabound(1) holds info about columns, and rgsabound(2) about rows
End Type

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (dest As _
  Any, source As Any, ByVal bytes As Long)
Private Const VT_BYREF = &H4000&

' Fills a SAFEARRAY structure for the supplied array.
'
' The information contained in the SAFEARRAY structure allows
' the caller to identify the number of dimensions and the
' number of elements for each dimension (among other things).
' Element information for each dimension is stored in a
' one-based sub-array of SAFEARRAYBOUND structures (rgsabound).
'
' TheArray    The array to get information on.
' ArrayInfo    The output SAFEARRAY structure.
'
' RETURNS     The number of dimensions of the array
'          or zero if the array isn't dimensioned

Function GetArrayInfo(TheArray As Variant, ArrayInfo As SAFEARRAY) As Boolean
  Dim lp As Long     ' work pointer variable
  Dim VType As Integer ' the VARTYPE member of the VARIANT structure

  ' Exit if no array supplied
  If Not IsArray(TheArray) Then Exit Function

  With ArrayInfo
    ' Get the VARTYPE value from the first 2 bytes of the VARIANT structure
    CopyMemory VType, TheArray, 2

    ' Get the pointer to the array descriptor (SAFEARRAY structure)
    ' NOTE: A Variant's descriptor, padding & union take up 8 bytes.
    CopyMemory lp, ByVal VarPtr(TheArray) + 8, 4

    ' Test if lp is a pointer or a pointer to a pointer.
    If (VType And VT_BYREF) <> 0 Then
      ' Get real pointer to the array descriptor (SAFEARRAY structure)
      CopyMemory lp, ByVal lp, 4
    End If

    ' Fill the SAFEARRAY structure with the array info
    ' NOTE: The fixed part of the SAFEARRAY structure is 16 bytes.
    CopyMemory ArrayInfo.cDims, ByVal lp, 16

    ' Ensure the array has been dimensioned before getting SAFEARRAYBOUND
    ' Information
    If ArrayInfo.cDims > 0 Then
      ' Fill the SAFEARRAYBOUND structures with the array info
      CopyMemory .rgsabound(1), ByVal lp + 16, _
        ArrayInfo.cDims * Len(.rgsabound(1))

      ' So caller knows there is information available for the array in
      ' output SAFEARRAY
      GetArrayInfo = ArrayInfo.cDims
    End If

  End With

End Function