Performance problem stripping blanks

[Capoerista]

Hi All,

I've inherited support of a VB application which is having performance problems processing large text files. I have narrowed down the problem to the for loop section. The aim is to read in an rtf file, then output a copy of the file with rightmost blanks stripped.

The routine is

Function TrimTrailingBlankLines(Indat As String) As String
Dim Res As String
        Dim lins, ln, Lin

    Debug.Print "TrimTrailing... split"

        lins = Split(Trim(Indat), vbCrLf)
        
    Debug.Print "TrimTrailing... for"
        
        For ln = UBound(lins) To 0 Step -1
            Lin = lins(ln)
            If Trim(left(Lin, 4)) = "____"
            Then
                Lin = Space(Len(Lin))
            End If
            If Len(Res) = 0 Then
                If Trim(Lin) <> "" Then
                    Res = Lin
                End If
            Else
                Res = Lin & vbCrLf & Res
            End If
        Next
    Debug.Print "... TrimTrailing"

    TrimTrailingBlankLines = Res
End Function

For context the code that calls this routine is

  Debug.Print "Read form frmEmail_2_OTC"
   Load frmEmail_2_OTC
   Set TS = fso.OpenTextFile(INPUT_FILE, ForReading)
   frmEmail_2_OTC.rtfTemp.TextRTF = TS.ReadAll
   TS.Close
  Debug.Print "close form"
   NewIn = fso.GetParentFolderName(INPUT_FILE) & "\OrigRTF_" & fso.GetFileName(INPUT_FILE)
   If fso.FileExists(NewIn) Then
       Kill NewIn
   End If
        
   Name INPUT_FILE As NewIn
        
   'Name Run_File as
   Set TS = fso.OpenTextFile(INPUT_FILE, ForWriting, True)
        
  Debug.Print "Trim Blanks"
   TS.Write TrimTrailingBlankLines(Trim(frmEmail_2_OTC.rtfTemp.Text)) & vbCrLf
    TS.Close
   Debug.Print "End Trim Blanks"

The input file is approx 3Mb and takes about 20 mins on a 2Ghz PC with 256Mb memory to get through this routine. Is the main problem doing a len on an increasingly large string? Any pointers on possible improvements would be greatly appreciated.

Cheers

Ade

P.S. I'm not sure why the loop is going backwards through the array.

 

[Swi]

To strip trailing spaces on a string you can use RTrim:

Ex. -

MsgBox Len(RTrim$(" Test "))

This will give a result of 6.

Swi

 

[Swi]

The other bit of code that looks like it is hogging memory is Res = Lin & vbCrLf & Res.

Appending strings in VB is very slow.

Swi

 

[bjd4jc]

Is this something that could be done with a regular expression? I am very new to them so I don't have any idea what it would look like...