能帮我解释一下吗.谢谢

Function Drawbar(drvpath)
         dim fso,drvpathroot,d,size,totalsize,barsize
         set fso=server.createobject("scripting.filesystemobject")
         drvpathroot=server.mappath("images")
         drvpathroot=left(drvpathroot,(instrrev(drvpathroot,"\")-1))
         set d=fso.getfolder(drvpathroot)
         totalsize=d.size
         
         drvpath=server.mappath(drvpath)         
         set d=fso.getfolder(drvpath)
         size=d.size
         
         barsize=cint((size/totalsize)*150)
         Drawbar=barsize
     End Function