用流(stream)技术做下载

function dl(f,n)
 on error resume next
 Set S=CreateObject("Adodb.Stream")
 S.Mode=3
 S.Type=1
 S.Open
 S.LoadFromFile(f)
 if Err.Number>0 then
  Response.Status="404"
 else
  Response.ContentType="application/octet-stream"
  Response.AddHeader "Content-Disposition:","attachment; filename=" & n
  Range=Mid(Request.ServerVariables("HTTP_RANGE"),7)
  if Range="" then
   Response.BinaryWrite(S.Read)
  else
   S.position=Clng(Split(Range,"-")(0))
   Response.BinaryWrite(S.Read)
  End if
 end if
 Response.End
end function

函数使用示例：
call dl(Server.MapPath("../download/07.zip"),"07.zip")