function StrReplace(str, oldPattern, newPattern: string; flags: TReplaceFlags): string;
var
  i, p, c, l, z, q: Integer;
  s, o: string;
  f: Boolean;
begin
  l := Length(str);
  z := Length(oldPattern);
  if ((l > 0) and (z > 0) and (oldPattern <> newPattern)) then
  begin
    Result := '';
    s := str;
    o := oldPattern;
    if (rfIgnoreCase in flags) then
    begin
      s := LowerCase(s);
      o := LowerCase(o);
    end;
    i := 1;
    c := 0;
    case (rfReplaceAll in flags) of
      True:
      begin
        q := i;
        repeat
          for p := 1 to z do
          begin
            f := (s[((i + p) - 1)] = o[p]);
            if not f then
              Break;
          end;
          if f then
          begin
            if (c > 0) then
              Result := (Result + Copy(str, q, c));
            Result := (Result + newPattern);
            i := ((i + z) - 1);
            q := (i + 1);
            c := 0;
          end else
            c := (c + 1);
          i := (i + 1);
        until (i > l);
        if (c > 0) then
          Result := (Result + Copy(str, q, c));
      end;
      False:
      begin
        repeat
          for p := 1 to z do
          begin
            f := (s[((i + p) - 1)] = o[p]);
            if not f then
              Break;
          end;
          i := (i + 1);
        until (f or (i > l));
        case f of
          True:
          begin
            i := (i - 1);
            if (i > 1) then
              Result := (Result + Copy(str, 1, (i - 1)));
            Result := (Result + newPattern);
            i := (i + z);
            if not (i > l) then
              Result := (Result + Copy(str, i, ((l - i) + 1)));
          end;
          False: Result := str;
        end;
      end;
    end;
  end else
    Result := str;
end;