I was working on a component to allow a "multi-post upload"; I had to
set it down for the moment in order to take care of more urgent work,
but I intend to get back on it next week.
It is a fairly simple server side script but it does require a client
side component that I currently have coded as a VB Application and
needs to be recoded as a downloadable .net component (it would be even
if this was a java applet, for cross browser compatability)
It was working, and the basic design is in place, but it could use some
code review and exception handling. It is pretty simple and should
allow for arbitrary small posts, and abitrarly large uploads, limitted
only by disk availability.
If anyone uses this, or improves it, please let me know so I can
benefit from the code review.
Basic concept:
1. client creates a connection and gets a hash from server
2. client reads file and post "postSize" bytes - server side opens file
associated with hash, seek() to offset sent by client and writes the
data sent. -repeat
3. client sends a completed signal.
There could be some optimization if you kept the file open between
posts, but that brings up the
The files are:
gigaUploadClient.vb - a class that implements the client
UploadServlet.aspx
UploadServlet.aspx.vb - implements the server side storage
uploadTester.vb - The code behind a form demonstrating how to use the
client.
uploadTester.vb:
Public Class uploadTester
Private _uploader As gigaUploadClient
Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnSend.Click
btnSend.Enabled = False
Dim postSize As Integer
If Not Integer.TryParse(txtPostSizeKB.Text, postSize) Then
MessageBox.Show("<" + txtPostSizeKB.Text + "> is not a
valid integer!")
Return
End If
_uploader = New gigaUploadClient(txtFile.Text, txtUrl.Text,
postSize)
Dim upldThrd As New Threading.Thread(AddressOf
_uploader.SendFile)
upldThrd.Start()
End Sub
Private Sub btnUpdate_Click(ByVal sender As System.Object, ByVal e
As System.EventArgs) Handles btnUpdate.Click
lblProgress.Text = _uploader.GetProgress + " : " +
Math.Round(_uploader.GetProgressFraction * 100).ToString + "%"
btnSend.Enabled = Not _uploader.IsRunning()
End Sub
End Class
********************************************************************************************
UploadServlet.aspx:
<%@ Page Language="VB" AutoEventWireup="false"
CodeFile="UploadServlet.aspx.vb" Inherits="_UploadServlet" %>
********************************************************************************************
Imports System
Imports System.IO
Partial Class _UploadServlet
Inherits System.Web.UI.Page
Private savePath As String
Private Const readBlockSize As Integer = 10240
Public Sub New()
Dim settings As Configuration.AppSettingsReader = New
Configuration.AppSettingsReader()
Try
savePath = settings.GetValue("savePath", GetType(String))
Catch
savePath = "c:\temp\uploader"
End Try
Try
If Not Directory.Exists(savePath) Then
Directory.CreateDirectory(savePath)
End If
Catch ex As Exception
End Try
End Sub
Protected Sub Page_Load(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Load
ProcessUploadRequest()
End Sub
Private Sub restartUpload(ByVal fpath As String)
'/* Find the seek position */
Dim seekPos As Long = 0
Try
seekPos = Long.Parse(Request("offset"))
Catch nex As Exception
Response.Write("-1")
Return
End Try
Dim fout As FileStream
If seekPos > 0 Then
'* Open a RandomAccessFile so that we can seek on it.
fout = File.Create(fpath, FileMode.OpenOrCreate,
FileOptions.RandomAccess)
'this seek call takes significant time when the file is
big, so only do
'it if we get a seekposition which suggest a resume upload
fout.Seek(seekPos, IO.SeekOrigin.Begin)
'truncate the file to the restart position
fout.Close()
Response.Output.Write(seekPos.ToString)
Return
Else
Response.Write("-1")
Return
End If
End Sub
Private Sub SpoolFile(ByVal fpath As String)
Dim instr As Stream = Request.InputStream
If (Not Directory.Exists(Path.GetDirectoryName(fpath))) Then
Try
Directory.CreateDirectory(Path.GetDirectoryName(fpath))
Catch ex As Exception
End Try
End If
Dim fout As FileStream
If (File.Exists(fpath)) Then
fout = File.OpenWrite(fpath)
fout.Seek(0, SeekOrigin.End)
Else
fout = File.Create(fpath, FileMode.CreateNew)
End If
Dim b(readBlockSize) As Byte
Dim i As Integer
Do
i = Request.InputStream.Read(b, 0, readBlockSize)
fout.Write(b, 0, i)
Diagnostics.Debug.Print(Text.Encoding.ASCII.GetString(b, 0,
i))
Loop While (i = readBlockSize)
'Response.Write(fout.Length)
fout.Close()
End Sub
Public Sub ProcessUploadRequest()
Try
Response.ContentType = "text/html;charset=UTF-8"
Dim hash As String = Request("hash")
Dim cmd As String = Request("cmd")
Dim fname As String = Request("fname")
If "".Equals(fname) Or fname Is Nothing Then fname =
"downloadfile.dat"
Diagnostics.Debug.Print("cmd ::" + cmd)
Diagnostics.Debug.Print("fname ::" + fname)
If hash Is Nothing Then hash = "0" +
Guid.NewGuid().ToString + "1"
If ("").Equals(hash) Then hash = "0" +
Guid.NewGuid().ToString + "1"
Dim fpath As String = Path.Combine(Path.Combine(savePath,
hash), fname)
Diagnostics.Debug.Print("hash ::" + hash)
Select Case cmd
Case "getconnection"
Response.Output.Write(hash)
Response.Output.Close()
Return
Case "getstatus"
'this is and extra step for the current
configuration
'but it is useful if we want to implement a resume
upload.
'this is not currently implemented.
Diagnostics.Debug.Print("writing file to " + fpath)
If (File.Exists(fpath)) Then
'* The file exists on the server. A previous
upload has failed.
'* report back how many bytes have been written
Response.Output.Write(New
FileInfo(fpath).Length())
Else
'* report back that zero bytes have been
written
Response.Output.Write("0")
Response.Output.Close()
End If
Case "completeupload"
' this is where we could do any clean up or file
moving that we want
Response.Output.Write("Success. Bytes written: " +
FileLen(fpath).ToString)
Return
Case "restart"
restartUpload(fpath)
Response.Output.Close()
Return
Case "spoolfile"
'this is the case of spooling the file
If (hash Is Nothing) Then
Response.Output.Write("null hash, null cmd is
not valid")
End If
SpoolFile(fpath)
Response.Output.Close()
Return
End Select
Catch e As Exception
Response.Output.Write("failed")
Response.Output.Write(e.Message)
Diagnostics.Debug.Print(e.Message)
End Try
End Sub
End Class
***********************************************************************************************
Imports System
Imports System.IO
Imports System.Net
Public Class gigaUploadClient
Private _cli As WebClient
Private _hash As String
Private _fileSize As Long
Private _reader As IO.Stream
Private _uploadUrl As String
Private _sourceFile As String
Private _postSize As Long
Private _curPos As Long = 0
Private _lockObj As New Object
Private _isRunning As Boolean = False
Public Sub New(ByVal sourceFile As String, ByVal uploadUrl As
String, ByVal postSize As Integer)
_uploadUrl = uploadUrl
_sourceFile = sourceFile
_postSize = postSize
End Sub
Public Sub SendFile()
_isRunning = True
_cli = New WebClient()
_cli.QueryString.Add("cmd", "getconnection")
'cli.QueryString.Add("hash", "")
_hash = _cli.DownloadString(_uploadUrl)
'begin hack
'trim off any whitespace. think this was because I used a
WriteLine() on the servlet. duh!
_hash.TrimEnd(Constants.vbCrLf.ToCharArray)
If _hash.EndsWith(Constants.vbCrLf) Then
_hash = _hash.Substring(0, _hash.Length - 2)
End If
'end hack
Dim fileOffset As Long = getStatus()
If fileOffset > 0 Then
restartTransfer(fileOffset)
End If
spoolFile()
_isRunning = False
End Sub
Private Function getStatus() As Long
_cli.QueryString.Clear()
_cli.QueryString.Add("cmd", "getstatus")
_cli.QueryString.Add("hash", _hash)
_cli.QueryString.Add("fname", Path.GetFileName(_sourceFile))
Dim fileOffsetStr As String = _cli.DownloadString(_uploadUrl)
Dim fileOffset As Long
If Long.TryParse(fileOffsetStr, fileOffset) Then
Return fileOffset
Else
Return 0
End If
End Function
Private Sub restartTransfer(ByVal offset As Long)
_cli.QueryString.Clear()
_cli.QueryString.Add("cmd", "restart")
_cli.QueryString.Add("hash", _hash)
_cli.QueryString.Add("fname", Path.GetFileName(_sourceFile))
Dim fileOffsetStr As String = _cli.DownloadString(_uploadUrl)
SyncLock _lockObj
_curPos = offset
End SyncLock
End Sub
Private Sub confirmFileFinished()
_cli.QueryString.Clear()
_cli.QueryString.Add("cmd", "completeupload")
_cli.QueryString.Add("fname", Path.GetFileName(_sourceFile))
_cli.QueryString.Add("hash", _hash)
Dim resp As String = _cli.DownloadString(_uploadUrl)
End Sub
Private Sub spoolFile()
Dim out As IO.Stream
_fileSize = FileLen(_sourceFile)
Const readBufferSize As Integer = 4096
Dim b(readBufferSize) As Byte
Dim postSize As Integer = _postSize * 1024
Dim i As Integer
Dim bytesSpooled As Long = 0
_reader = File.OpenRead(_sourceFile)
If _curPos > 0 Then
_reader.Seek(_curPos, SeekOrigin.Begin)
End If
Do
_cli.QueryString.Clear()
_cli.QueryString.Add("cmd", "spoolfile")
_cli.QueryString.Add("hash", _hash)
_cli.QueryString.Add("fname",
Path.GetFileName(_sourceFile))
_cli.Headers.Add("Content-Type",
"application/octet-stream")
'don't write offset unless we need to resume an upload
'cli.QueryString.Add("offset", curPos.ToString)
out = _cli.OpenWrite(_uploadUrl)
Dim bytesSpooledThisPost As Integer = 0
Do
i = _reader.Read(b, 0, readBufferSize)
out.Write(b, 0, i)
bytesSpooledThisPost += i
bytesSpooled += i
SyncLock _lockObj
_curPos = bytesSpooled
End SyncLock
Loop While (i = readBufferSize And bytesSpooledThisPost <
postSize)
out.Close()
Loop While (i = readBufferSize) ' i will be less then
readBufferSize when we reach the end of the file
End Sub
Public Function GetProgressFraction() As Double
SyncLock _lockObj
Return _curPos / _fileSize
End SyncLock
End Function
Public Function GetProgress() As String
SyncLock _lockObj
Return Math.Round(_curPos / 1024).ToString + "kb of " +
Math.Round(_fileSize / 1024).ToString + "kb transfered"
End SyncLock
End Function
Public Function IsRunning() As Boolean
Return _isRunning
End Function
End Class
