XProfan

string furi(string s){

    return "file:///"+translate$(translate$(s,"\\","/"),"//","/")

}

Proc fURI

    Parameters s$
    Declare x%

    If Left$(Lower$(s$),5) = "file:"

        x% = 5 : While Mid$(s$,x% + 1,1) = "/" : Inc x% : EndWhile
        s$ = Right$(s$,Len(s$) - x%)

    EndIf

    Return "file:///"+translate$(translate$(s$,"\\","/"),"//","/")

EndProc

cls
print fURI("file:///c:/pfad/datei.txt")
print fURI("c:/pfad/datei.txt")
waitkey
end