Splitting a large file into smaller files

[wild_bill]

We had a process that split large files into smaller files be reading and writing line by line. This fixed the out of memory exceptions we were having, but it took hours to complete. I rewrote this method, so it is way faster, and doesn't cause memory exceptions.

Private Function SplitFile( _
    ByVal inputFileName As String, ByVal outputFileName As String, ByVal numberOfFiles As Integer) _
    As List(Of String)
        Dim returnList As New List(Of String)
        Try
            Dim outputFileExtension As String = IO.Path.GetExtension(outputFileName)
            outputFileName = outputFileName.Replace(outputFileExtension, "")
            Dim sr As New IO.StreamReader(inputFileName)
            Dim fileLength As Long = sr.BaseStream.Length
            Dim baseBufferSize As Integer = CInt(fileLength \ numberOfFiles)
            Dim finished As Boolean = False
            Dim fileCount As Integer = 1
            Do Until finished
                Dim bufferSize As Integer = baseBufferSize
                Dim originalPosition As Long = sr.BaseStream.Position
                'find line first line feed after the base buffer length
                sr.BaseStream.Position += bufferSize
                If sr.BaseStream.Position < fileLength Then
                    Do Until sr.Read = 10
                        bufferSize += 1
                    Loop
                    bufferSize += 1
                Else
                    bufferSize = CInt(fileLength - originalPosition)
                    finished = True
                End If
                'write the chunk of data to a buffer in memory
                sr.BaseStream.Position = originalPosition
                Dim buffer(bufferSize - 1) As Byte
                sr.BaseStream.Read(buffer, 0, bufferSize)
                'write the chunk of data to a file
                Dim outputPath As String = outputFileName & fileCount.ToString & outputFileExtension
                returnList.Add(outputPath)
                My.Computer.FileSystem.WriteAllBytes( _
                outputPath, buffer, False)
                fileCount += 1
            Loop
        Catch ex As Exception
            Console.Write(ex.ToString)
        End Try
        Return returnList
    End Function