RtlCompareMemory Help please[RESOLVED]

[Adrian26]

Hi all, Please could someone tell me how i use the RtlCompareMemory api to compare 2 2d arrays.

Thanks in advance...

[penagate]

I'm sure you have a more imaginative example in mind, but here:

(Note, this is very ugly, and could be optimised by storing LBound/UBound values. Even better, use zero-based dimensions exclusively, that will be much faster overall).

Private Declare Function RtlCompareMemory Lib "ntdll" ( _
    ByRef Source1 As Any, _
    ByRef Source2 As Any, _
    ByVal Length As Long _
) As Long
'
 
Private Sub Command1_Click()
    Dim array1(3, 6) As Long
    Dim array2(3, 6) As Long
 
    array1(2, 4) = 50
    array2(2, 4) = 50
 
    ' Usage to compare two 2D arrays:
    Dim size1 As Long, size2 As Long
 
    size1 = (UBound(array1, 1) - LBound(array1, 1)) * _
            (UBound(array1, 2) - LBound(array1, 2)) * _
            LenB(array1(LBound(array1, 1), LBound(array1, 2)))
 
    size2 = (UBound(array2, 1) - LBound(array2, 1)) * _
            (UBound(array2, 2) - LBound(array2, 2)) * _
            LenB(array2(LBound(array2, 1), LBound(array2, 2)))
 
    If (size1 = size2) Then
        If (RtlCompareMemory(ByVal VarPtr(array1(LBound(array1, 1), LBound(array1, 2))), _
                             ByVal VarPtr(array2(LBound(array2, 1), LBound(array2, 2))), _
                             size1) = size1) _
        Then
            MsgBox "Arrays are equal"
        Else
            MsgBox "Arrays are not equal"
        End If
    Else
        MsgBox "Arrays have different dimensions"
    End If
End Sub

[penagate]

If you do use zero-based dimensions, it is a hell of a lot neater.

Dim size1 As Long, size2 As Long
 
    size1 = UBound(array1, 1) * UBound(array1, 2) * LenB(array1(0, 0))
    size2 = UBound(array2, 1) * UBound(array2, 2) * LenB(array2(0, 0))
    
    If (size1 = size2) Then
        If (RtlCompareMemory(ByVal VarPtr(array1(0, 0)), _
                             ByVal VarPtr(array2(0, 0)), _
                             size1) = size1) _
        Then
            MsgBox "Arrays are equal"
        Else
            MsgBox "Arrays are not equal"
        End If
    Else
        MsgBox "Arrays have different dimensions"
    End If

[moeur]

Penagate,
You and Joacim like varptr don't you?

If RtlCompareMemory(array1(0, 0), array2(0, 0), size1) = size1 then

[penagate]

VarPtr() does my dishes.

[Adrian26]

Excellent! works like a dream many thanks...

One last question though, the way you work out the array sizes can i use the same method for the copyMemory api, again the arrays are 2d.

Cheers...

[penagate]

Yes you can.

[Adrian26]

Now that was a fast reply, thanks once again.

[penagate]

No problem!

[Merri]

If interested, there is a guide in the FAQ section on how to use one dimensional arrays instead of multidimensional