求救老司机，为什么会写两遍

代码如下：
Dim biData,PostData,Size,filename
biData="":PostData="":Size=""
Size=Request.TotalBytes
if Size>0 then
//PostData=Request.BinaryRead(Size)
PostData=sTb(Request.BinaryRead(Size))
Response.Write(PostData)
Function sTb(vin)
Const adTypeText = 2
Dim BytesStream,StringReturn
Set BytesStream = Server.CreateObject("ADODB.Stream")
With BytesStream
.Type = adTypeText
.Open
.WriteText vin
.Position = 0
.Charset = "utf-8"
.Position = 2
StringReturn = .ReadText
End With
BytesStream.WriteText StringReturn
BytesStream.SaveToFile("F:\Code\daima\vbWeb\1.txt")
BytesStream.Close
Set BytesStream = Nothing
sTb = StringReturn
End Function
end if
%>