delphi 判断目录是否可写

FUNCTION WritableDir(CONST Dir : STRING) : BOOLEAN;
  VAR
    FIL : FILE;
    N   : STRING;
    I   : Cardinal;

  BEGIN
    REPEAT
      N:=IncludeTrailingPathDelimiter(Dir);
      FOR I:=1 TO 250-LENGTH(N) DO N:=N+CHAR(RANDOM(26)+65)
    UNTIL NOT FileExists(N);
    Result:=TRUE;
    TRY
      AssignFile(FIL,N);
      REWRITE(FIL,1)
    EXCEPT
      Result:=FALSE
    END;
    IF Result THEN BEGIN
      CloseFile(FIL); 
      ERASE(FIL)
    END
  END;

http://blog.csdn.net/genispan/article/details/10004487