Re: UUCP documentation!

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Article #5337

#5337

From: Russell Schulz
Date: Tue, 03 Jan 1995 00:44

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(followups redirected; posted and mailed)

jorge@laser.satlink.net (Jorge Cwik) writes:

> Every decent Uucp reference should come with the 'g' checksum
> algorithm. Although all the ones I've seen include code in C,
> and not in pascal as you requested in another post.

it's fairly trivial to express in some Pascal-derived languages, like Turbo:
(unfortunately, my version has no word-based xor builtin)

function wxor(w1,w2: word): word;

begin
  wxor := (w1 or w2)-(w1 and w2);
end;

function checksumof(apacket: datapackett; completelen: integer): word;

var
  check1: word;
  check2: word;
  i: integer;
  onebyte: byte;

{check1 and check2 have to be 16-bit quantities, or do a lot of AND $FFFF}

{this routine copied from Taylor's UUCP Internals FAQ}

begin
  check1 := $ffff;
  check2 := 0;

  for i := 1 to completelen do
    begin
      if (check1 and $8000)=0 then
        check1 := check1 shl 1
      else
        check1 := (check1 shl 1)+1;

      onebyte := apacket[i];

      inc(check1,onebyte);

      inc(check2,wxor(check1,completelen-i+1));

      if (onebyte=0) or (check1<onebyte) then
        check1 := wxor(check1,check2);
    end;

  checksumof := check1;
end;
-- 
Russell Schulz  russell@alpha3.ersys.edmonton.ab.ca  ersys!rschulz  Shad 86c

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From: russell@alpha3.ersys.edmonton.ab.ca (Russell Schulz)
Newsgroups: comp.mail.uucp,alt.bbs.pcbuucp,alt.sys.amiga.uucp,can.uucp,de.comm.uucp,tor.uucp
Subject: Re: UUCP documentation!
Message-ID: <950102.174411.1W0.rusnews.w164w@alpha3.ersys.edmonton.ab.ca>
Date: Mon, 2 Jan 1995 17:44:11 -0700
References: <3dsl1h$drd@lightning.powertech.no> <ac33Xc1w165w@laser.satlink.net>
Reply-To: russell@alpha3.ersys.edmonton.ab.ca (Russell Schulz)
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