VB.NET多线程文件读写

现在，流行的下载工具都使用了多线程的方式，这样比单线程下载快了很多。

 

不过那些通常都不是用VB.NET写的，网上可以找到的这方面的资料也比较少。自己琢磨了几天，同时也借助于网友的帮助，解决了这个问题。

 

下边上代码。

 

Imports System.IO
Imports System.Threading
Imports System.Text
Public Class Form1
    Private p As String = "" '文件路径
    Private fLength As Integer
    Private fl As Integer = 102400 '定义缓冲区大小
    Private fStart As Integer = 0 '定义读取起始位置
    Private m As Integer = 1
    Private fCount As Integer = 0 '分块数
    Private cInte As Integer = 0 '当前块

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        OpenFileDialog1.ShowDialog()
        TextBox1.Text = OpenFileDialog1.FileName
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        p = TextBox1.Text
        Dim a As New FileInfo(p)
        fLength = a.Length
        fStart = 0
        Dim u As Thread
        fStart = -fl
        Dim c, d As Double
        c = Int(fLength / fl)
        d = fLength / fl
        If c < d Then
            fCount = c + 1
        Else
            fCount = d
        End If
        For i As Integer = 1 To ThreadCount.Text
            u = New Thread(AddressOf Work)
            u.IsBackground = True
            u.Name = i
            u.Start()
        Next
    End Sub

    Sub Work()
        SyncLock Thread.CurrentThread
            Do While Not cInte >= fCount
                fStart += fl
                cInte += 1
                ReadData(fStart, fl, cInte)
            Loop
            If cInte = fCount Then
                Dim temppath As String = "E:\1\"
                '========合并文件=========
                Dim pm As New System.Diagnostics.Process()
                pm.StartInfo.FileName = "cmd.exe"
                pm.StartInfo.UseShellExecute = False
                pm.StartInfo.CreateNoWindow = True
                pm.StartInfo.RedirectStandardInput = True
                pm.StartInfo.RedirectStandardOutput = True
                pm.Start()
                Dim temp As String = ""
                Dim fEx As New FileInfo(p)

                For i As Integer = 1 To fCount
                    If temp = "" Then
                        temp = "E:\1\" & fEx.Name.Replace(fEx.Extension, "." & i & fEx.Extension)
                    Else
                        temp = temp & " + " & "E:\1\" & fEx.Name.Replace(fEx.Extension, "." & i & fEx.Extension)
                    End If
                Next
                'MsgBox(temp)
                pm.StandardInput.WriteLine("copy /b " & temp & " " & temppath & "OK.txt")
                pm.StandardInput.WriteLine("exit")
                pm.WaitForExit()
            End If
        End SyncLock
    End Sub

    '读取指定位置的内容
    Sub ReadData(ByVal Start As Integer, ByVal l As Integer, ByVal cuinte As Integer)
        Dim u As New FileStream(p, FileMode.Open, FileAccess.Read)

        Dim sBy(l - 1) As Byte
        u.Seek(Start, SeekOrigin.Begin)
        u.Read(sBy, 0, sBy.Length)
        u.Close()
        u.Dispose()
        writeData(cuinte, sBy)
    End Sub


    '写文件
    Sub writeData(ByVal cuinte As Integer, ByVal data As byte())
        Try
             Dim fEx As New FileInfo(p)
             Dim TEMP As String = "c:\" & fEx.Name.Replace(fEx.Extension, "." & cuinte & fEx.Extension)
 Dim u As New FileStream(TEMP, FileMode.OpenOrCreate, FileAccess.Write)
 Dim Bw As New System.IO.BinaryWriter(u)
 Bw.Write(data)
 u.Close()
 u.Dispose()
 Bw.Close() 

        Catch ex As Exception
            Err.Clear()
            Exit Sub
        End Try
    End Sub


    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        End
    End Sub

 

在写上边代码的时候，碰到了一个文件拆分后再合并后，文件被损坏的问题，详见：http://topic.csdn.net/u/20100716/11/4addfa0d-db8e-4604-9e7b-f2e14958a59e.html

 

在此也感谢各位网友的帮助