asp中自定义文件下载

可以用流下载(耗内存，少用)或直接转到该文件.

<%

Const USE_STREAM = 0 '0.不用流(Ad***.Stream)下载 1.用流下载
Const ALLOW_FILE_EXT = "rar,zip,chm,doc,xls,swf,mp3,gif,jpg,jpeg,png,bmp" '允许下载的文件的扩展名，防止源代码被下载

Dim sDownFilePath '下载文件路径
sDownFilePath = Trim(Request("FilePath"))
'或者根据传过来的文件ID从数据库中获取文件路径

'如果 sDownFilePath 为绝对路径，一定要将 sDownFilePath 转换为相对 本文件的相对路径

'sDownFilePath = "fo***.swf"

Call DownloadFile(sDownFilePath)

Function DownloadFile(s_DownFilePath)
    '判断有没传递文件名
    If IsNull(s_DownFilePath) = True Or Trim(s_DownFilePath) = "" Then
        OutputErr "错误：先确定要下载的文件，下载失败"
    End If

    '判断扩展名是否合法
    Dim s_FileExt
    s_FileExt = Mid(s_DownFilePath, InstrRev(s_DownFilePath, ".")+1)
    If InStr("," & ALLOW_FILE_EXT & ",", "," & s_FileExt & ",") <= 0 Then
        OutputErr "错误：文件类型（" & s_FileExt & "）不允许被下载，下载失败"
    End If
   
    s_DownFilePath = Replace(s_DownFilePath, "", "/")

    '为了安全，某些目录禁止下载文件，在这里处理
    '
   
    '检测服务器是否支持fso
    Dim o_Fso
    On Error Resume Next
    Set o_Fso = Se***r.CreateObject("Sc***ting.FileSystemObject")
    If Er***umber <> 0 Then
        Er***lear
        OutputErr "错误：服务器不支持fso组件，下载失败"
    End If

    '取得文件名，文件大小
    Dim s_FileMapPath
    Dim o_File, s_FileName, n_FileLength
    s_FileMapPath = Se***r.MapPath(s_DownFilePath)
    If (o_***.FileExists(s_FileMapPath)) = True Then
        Set o_File = o_***.GetFile(s_FileMapPath)
        s_FileName = o_***e.Name
        n_FileLength = o_***e.Size
        o_***e.Close
    Else
        OutputErr "错误：文件不存在，下载失败"
    End If
    Set o_Fso = Nothing

    '判断是否下载的文件大小超过限制
    '   
   
    '如果不是用流下载，直接转到该文件
    If USE_STREAM = 0 Then
        Re***nse.Redirect sDownFilePath
        Re***nse.end
    End If

    '检测服务器是否支持Ad***.Stream
    On Error Resume Next
    Set o_Stream = Se***r.CreateObject("Ad***.Stream")
    If Er***umber <> 0 Then
        Er***lear
        OutputErr "错误：服务器不支持Ad***.Stream组件，下载失败"
    End If

    o_***eam.Tyep = 1
    o_***eam.Open
    o_***eam.LoadFromFile s_FileMapPath

    Re***nse.Buffer = True
    Re***nse.Clear
    Re***nse.AddHeader "Content-Disposition", "attachment; filename=" & s_FileName
    Re***nse.AddHeader "Content-Length", n_FileLength
    Re***nse.CharSet = "UTF-8"
    Re***nse.ContentType = "application/octet-stream"
    Re***nse.BinaryWrite o_***eam.Read
    Re***nse.Flush

    o_***eam.Close
    Set o_Stream = Nothing

End Function

Sub OutputErr(s_ErrMsg)
    Re***nse.Write "" & s_ErrMsg & ""
    Re***nse.End
End Sub

%>

http://www.cnblogs.com/jiny-z/archive/2006/08/29/489102.html