[Oberon] Removing unnecessary and embedded RETURNs.

[joerg.straube at iaeth.ch]

Peter

The idea with the state machine is good.
One remark:
I don’t understand you remark “ReadText is external to this byte padding”
In my point of view in the ELSE part of state 3 you would have to strip the stuffed period.
In other words: you would have to reposition and copy the Files.Write(R, ch); to almost all your cases

br
Jörg

Von: Oberon <oberon-bounces at lists.inf.ethz.ch> im Auftrag von peter at easthope.ca <peter at easthope.ca>
Datum: Sonntag, 12. November 2023 um 15:58
An: oberon at lists.inf.ethz.ch <oberon at lists.inf.ethz.ch>
Betreff: Re: [Oberon] Removing unnecessary and embedded RETURNs.
This is my alternative Mail.ReadText with no RETURN.  ReportError was
helpful in debugging; probably can be deleted now.

Apology for the verbose comments.  Added to help a non-expert
understand the non-obvious activity.  =8~)

I wonder whether this use of CASE is good practise.  Observations?

Thanks,                   ... P.L.

        PROCEDURE ReportError(c: CHAR);
        BEGIN
                Texts.WriteString(W, "Mail.ReadText(): LF absent at CASE "); Texts.Write(W, c);
                Texts.Write(W, "."); Texts.WriteLn(W);
                Texts.Append(Oberon.Log, W.buf); HALT(6)
        END ReportError;

        (* According to Post Office Protocol, the end of a message body is
                marked by character sequence CR LF "." CR LF.
                A message line can begin with a period.  To distinguish from end-of-message,
                the message sender prepends an additional period which is removed before the
                message is displayed to the recipient.  ReadText is external to this byte padding.
                https://en.wikipedia.org/wiki/Post_Office_Protocol
                https://tools.ietf.org/html/rfc1939#section-3 *)
        PROCEDURE ReadText(S: NetTools.Session; VAR R: Files.Rider);
                VAR
                        buffer: ARRAY BufLen OF CHAR;
                        len, readLen, i: SIGNED32;
                        ch: CHAR;
                        progress: CHAR; (*
                                "0"= continuing
                                "1"= CR
                                "2"= CR LF
                                "3"= CR LF "."
                                "4"= CR LF "." CR
                                "5"= CR LF "." CR LF = end-of-message; or no more characters *)
        BEGIN
                readLen := 0;
                i := readLen;
                progress := "0";
                WHILE progress < "5" DO (* Write byte to the MailMessages file. *)
                        IF i = readLen THEN (* More characters required. *)
                                len := NetSystem.Available(S.C);
                                IF (len = 0) & (NetSystem.State(S.C) # NetSystem.inout) THEN
                                        progress := "5"
                                ELSE
                                        IF len > (BufLen-2) THEN readLen := BufLen-2 ELSE readLen := len END;
                                        NetSystem.ReadBytes(S.C, 0, readLen, buffer);
                                        DEC(len, readLen);
                                        i := 0
                                END
                        ELSE (* i < readLen. character available *)
                                ch := buffer[i];
                                CASE progress OF
                                        "0": IF ch = Strings.CR THEN progress := "1" END |
                                        "1": IF ch = Strings.LF THEN progress := "2" ELSE ReportError(progress) END |
                                        "2": IF ch = Strings.CR THEN progress := "1"
                                                ELSIF ch = "." THEN progress := "3" ELSE progress := "0" END |
                                        "3": IF ch = Strings.CR THEN progress := "4" ELSE progress := "0" END |
                                        "4": IF ch = Strings.LF THEN progress := "5" ELSE ReportError(progress) END
                                END;
                                Files.Write(R, ch);
                                INC(i)
                        END
                END
        END ReadText;

-
VoIP:   +1 604 670 0140
work: https://en.wikibooks.org/wiki/User:PeterEasthope

--
Oberon at lists.inf.ethz.ch mailing list for ETH Oberon and related systems
https://lists.inf.ethz.ch/mailman/listinfo/oberon
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.inf.ethz.ch/pipermail/oberon/attachments/20231113/3809c48b/attachment.html>