Option Explicit
'**********************************************************************
'* S2L8.bas - (Section 2, Lesson 8) SEEKING THROUGH MESSAGES
'*            This is the RTDX Host Client for Section 2, Lesson 8
'*
'* This example receives integer values 1-10 from the target, then uses
'* the Seek() method to read the values in reverse order.
'**********************************************************************

Const Success = &H0                     ' Method call is valid
Const Failure = &H80004005              ' Method call failed
Const ENoDataAvailable = &H8003001E     ' No data was available.
                                        ' However, more data may be
                                        ' available in the future.
Const EEndOfLogFile = &H80030002        ' No data was available
                                        ' The end of the log file has
                                        ' been reached.


Sub main()
    
    Dim rtdx As Object
    Dim data As Integer
    Dim status As Long
    Dim nummsgs As Long
    Dim i As Long

    On Error GoTo Error_Handler

    ' Create an instance of the RTDX COM object
    Set rtdx = CreateObject("RTDX")

    ' Open channel ochan for reading
    status = rtdx.Open("ochan", "R")

    If status <> Success Then
        Debug.Print "Opening of channel ochan failed"
        GoTo Error_Handler
    End If

    '******************************************************************
    ' Insert code from Step #3 here - to get the total number of
    '                                 messages received by the host
    '******************************************************************
    status = rtdx.GetNumMsgs(nummsgs)
    
    If status <> Success Then
        Debug.Print "GetNumMsgs returned failure"
        GoTo Error_Handler
    End If
  
    ' Read data from beginning to end
    Debug.Print "Reading data from beginning to end"
    For i = 1 To nummsgs
        ' Read a 16-bit integer from the target
        status = rtdx.ReadI2(data)
        Select Case (status)
            Case Success
                Debug.Print "Value " & _
                            data & _
                            " was received from the target"
            Case ENoDataAvailable
                Debug.Print "No data is currently available"
            Case Failure
                Debug.Print "ReadI2 returned failure"
                Exit For
            Case Else
                Debug.Print "Unknown return code"
                Exit For
        End Select
    Next i

    '******************************************************************
    ' Insert code from Step #4 here - to rewind the log of data
    '******************************************************************
    status = rtdx.Rewind()
    
    If status <> Success Then
        Debug.Print "Rewind returned failure"
        GoTo Error_Handler
    End If

    ' Read data from end to beginning
    Debug.Print Chr(10) & "Reading data from end to beginning"
    For i = nummsgs To 1 Step -1

        '**************************************************************
        ' Insert code from Step #5 here - to Seek to a specific message
        '**************************************************************
        status = rtdx.Seek(i)
        
        If status <> Success Then
            Debug.Print "Seek returned failure"
            GoTo Error_Handler
        End If

        ' Read a 16-bit integer from the target
        status = rtdx.ReadI2(data)
        Select Case (status)
            Case Is = Success
                Debug.Print "Value " & _
                            data & _
                            " was received from the target"
            Case Is = ENoDataAvailable
                Debug.Print "No data is currently available"
            Case Is = Failure
                Debug.Print "ReadI2 returned failure"
                Exit For
            Case Else
                Debug.Print "Unknown return code"
                Exit For
        End Select
    Next i

    ' Close the channel
    status = rtdx.Close()

    ' Release the reference to the RTDX COM object
    Set rtdx = Nothing
    
    Exit Sub

Error_Handler:
Debug.Print "Error in COM method call"
Set rtdx = Nothing

End Sub