Question

我有这段代码来读取大文件并使用 buffer 以字节为单位写入它们，我想读取特定大小。例如，我有一个大小为 100 kb 的文件。我只想读取最后 30kb 并将它们保存到一个新文件中。我也不完全理解这个阅读器是如何工作的，但我想使用它所以它不能加载内存中的所有文件。

 Sub readthis(filein As String, fileout As Of String, startingposition as integer)
        Dim bytesRead As Integer
        Dim buffer(4096) As Byte
        Using inFile As New IO.FileStream(filein, FileMode.Open)
            Using outFile As New IO.FileStream(fileout, FileMode.Append, FileAccess.Write)
                Do
                    bytesRead = inFile.Read(buffer, 0, buffer.Length)
                    If bytesRead > 0 Then
                        outFile.Write(buffer, 0, bytesRead)
                    End If
                Loop While bytesRead > 0
            End Using
        End Using
    End Sub

Answer 1

试试这个：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    readthis("d:\log\tmp1.txt", "d:\log\tmp2.txt", 30)

End Sub

Sub readthis(filein As String, fileout As String, numlastbytes As Integer)

    Dim fs As New IO.FileStream(filein, FileMode.Open, FileAccess.Read)
    fs.Seek(-numlastbytes, SeekOrigin.End)
    Dim bytearray(numlastbytes) As Byte
    Dim numbytesread As Integer = fs.Read(bytearray, 0, numlastbytes)
    fs.Close()
    My.Computer.FileSystem.WriteAllBytes(fileout, bytearray, False)

End Sub

读取一个大文件，从一个字节位置开始写到一个新文件，vb.net

1 个答案: