根据字符串分隔大文件并插入回车

Question

VB新手。但一个朋友建议我用它来做我想做的事情。我有一个巨大的文本文件，我想在一个特定的字符串后插入回车。

除了下面的混乱，我该如何修改它来读取一个文件，然后一旦我们看到文本"ext"插入一个新的换行。我期望输入文件中的某一行产生大量回车。

目前，我已经设法模拟下面一起读取输入文件，直到行结束，并再次将其写入另一个文件。

Module Module1
Sub Main()
    Try
        ' Create an instance of StreamReader to read from a file. 
        ' The using statement also closes the StreamReader. 
        Using sr As StreamReader = New StreamReader("C:My Documentsinput.txt")
            Dim line As String
            ' Read and display lines from the file until the end of  
            ' the file is reached. 
            Using sw As StreamWriter = New StreamWriter("C:My Documentsoutput.txt")
                Do Until sr.EndOfStream
                    line = sr.ReadLine()
                    sw.WriteLine(line)
                    Console.WriteLine("done")
                Loop
            End Using
        End Using
    Catch e As Exception
        ' Let the user know what went wrong.
        Console.WriteLine("The file could not be read:")
        Console.WriteLine(e.Message)
    End Try
    Console.ReadKey()
End Sub

以下注释所做的更改…由于内存限制，在500mb的文件中失败:

    Sub Main()
    Try
        ' Create an instance of StreamReader to read from a file. 
        ' The using statement also closes the StreamReader. 
        Using sr As StreamReader = New StreamReader("C:My Documentsinput.txt")
            Dim line As String
            Dim term As String = "</ext>"
            ' Read and display lines from the file until the end of  
            ' the file is reached. 
            Using sw As StreamWriter = New StreamWriter("C:My Documentsoutput.txt")
                Do Until sr.EndOfStream
                    line = sr.ReadLine()
                    line = line.Replace(term, term + Environment.NewLine)
                    sw.WriteLine(line)
                    Console.WriteLine("done")
                Loop
            End Using
        End Using

Answer 1

由于你的行很长，你必须:

• 一次读/写一个字符
• 保存最后x个字符

• 如果最后x个字符等于你的术语，写一个新的行

  Dim term As String = "</ext>"
  Dim lastChars As String = "".PadRight(term.Length)
  Using sw As StreamWriter = New StreamWriter("C:My Documentsoutput.txt")
      Using sr As New System.IO.StreamReader("C:My Documentsinput.txt")
          While Not sr.EndOfStream
              Dim buffer(1) As Char
              sr.Read(buffer, 0, 1)
              lastChars &= buffer(0)
              lastChars = lastChars.Remove(0, 1)
              sw.Write(buffer(0))
              If lastChars = term Then
                  sw.Write(Environment.NewLine)
              End If
          End While
      End Using
  End Using
  

注意:这对Unicode文件不起作用。这里假设每个字符是一个字节