Does any one know of a faster method to do String.Split()?

Question

I am reading each line of a CSV file and need to get the individual values in each column. So right now I am just using:

values = line.Split(delimiter);
         


        

Answer 1

This is my solution:

Public Shared Function FastSplit(inputString As String, separator As String) As String()
        Dim kwds(1) As String
        Dim k = 0
        Dim tmp As String = ""

        For l = 1 To inputString.Length - 1
            tmp = Mid(inputString, l, 1)
            If tmp = separator Then k += 1 : tmp = "" : ReDim Preserve kwds(k + 1)
            kwds(k) &= tmp
        Next

        Return kwds
End Function

Here is a version with benchmarking:

Public Shared Function FastSplit(inputString As String, separator As String) As String()
        Dim sw As New Stopwatch
        sw.Start()
        Dim kwds(1) As String
        Dim k = 0
        Dim tmp As String = ""

        For l = 1 To inputString.Length - 1
            tmp = Mid(inputString, l, 1)
            If tmp = separator Then k += 1 : tmp = "" : ReDim Preserve kwds(k + 1)
            kwds(k) &= tmp
        Next
        sw.Stop()
        Dim fsTime As Long = sw.ElapsedTicks

        sw.Start()
        Dim strings() As String = inputString.Split(separator)
        sw.Stop()

        Debug.Print("FastSplit took " + fsTime.ToString + " whereas split took " + sw.ElapsedTicks.ToString)

        Return kwds
End Function

Here are some results on relatively small strings but with varying sizes, up to 8kb blocks. (times are in ticks)

FastSplit took 8 whereas split took 10

FastSplit took 214 whereas split took 216

FastSplit took 10 whereas split took 12

FastSplit took 8 whereas split took 9

FastSplit took 8 whereas split took 10

FastSplit took 10 whereas split took 12

FastSplit took 7 whereas split took 9

FastSplit took 6 whereas split took 8

FastSplit took 5 whereas split took 7

FastSplit took 10 whereas split took 13

FastSplit took 9 whereas split took 232

FastSplit took 7 whereas split took 8

FastSplit took 8 whereas split took 9

FastSplit took 8 whereas split took 10

FastSplit took 215 whereas split took 217

FastSplit took 10 whereas split took 231

FastSplit took 8 whereas split took 10

FastSplit took 8 whereas split took 10

FastSplit took 7 whereas split took 9

FastSplit took 8 whereas split took 10

FastSplit took 10 whereas split took 1405

FastSplit took 9 whereas split took 11

FastSplit took 8 whereas split took 10

Also, I know someone will discourage my use of ReDim Preserve instead of using a list... The reason is, the list really didn't provide any speed difference in my benchmarks so I went back to the "simple" way.