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Re: Reading beyond the end of file

From glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups comp.lang.c
Subject Re: Reading beyond the end of file
Date 2015-10-02 06:14 +0000
Organization Aioe.org NNTP Server
Message-ID <mul7bt$da9$1@speranza.aioe.org> (permalink)
References (6 earlier) <ln613gmyel.fsf@kst-u.example.com> <kfnvbawgadb.fsf@x-alumni2.alumni.caltech.edu> <lnd1x48w6b.fsf@kst-u.example.com> <kfnk2r69uwb.fsf@x-alumni2.alumni.caltech.edu> <S7kPx.64864$_E1.29939@fx01.iad>

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Richard Damon <Richard@damon-family.org> wrote:
> On 10/1/15 4:49 PM, Tim Rentsch wrote:

>> What is interesting (and was to me surprising) is that your
>> distinction here is made on the basis of what mechanism is used.
>> For me which mechanism is used doesn't matter - as long as EOF
>> can't be mistaken for a transmitted character value (and with
>> character values being the "normal" signal returned by getchar())
>> then I would call EOF an out-of-band value (or signal).
 
> By that analogy, the NUL at the end of a string is an 'out of band' signal?

In the usual case it is in-band, as '\0' could be written to a char
array, and if it isn't the string end character, it is valid.

If char is unsigned, then the usual EOF value of -1 is not in-band.

If, for some reason, X'00' wasn't legal, for example you can't
write one onto an even parity NRZI tape, a system could use it
as an out-of-band signal at the end of a buffer.
 
> As far as what is the 'normal' return of getchar(), that is 
> clearly an int, as that is how it is defined, and thus the 
> return value is the 'band'.

If char is signed then -1 is an in-band (actual character) value.
 
> By definition, the EOF signal needs to be something that can't be 
> mistaken for a transmitted character value, or it isn't reliable, in 
> band or out. Many communication protocols send data in octets, and use 
> special encoding to mark 'protocol' items in-band (which may require 
> tweaking normal data that might look like these items.) An out of band 
> method would be to use something outside of the data packets to transfer 
> the control information.

For bit-stuffed serial links, I would consider it out of band.A

Using escape characters, and escaping the escape character when
it really appears, is an interesting case.

-- glen

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Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-11 10:06 -0700
  Re: Reading beyond the end of file Geoff <geoff@invalid.invalid> - 2015-09-11 12:41 -0700
    Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-26 14:24 -0700
      Re: Reading beyond the end of file Geoff <geoff@invalid.invalid> - 2015-09-26 21:49 -0700
        Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-01 13:57 -0700
          Re: Reading beyond the end of file Geoff <geoff@invalid.invalid> - 2015-10-01 17:22 -0700
            Re: Reading beyond the end of file raltbos@xs4all.nl (Richard Bos) - 2015-10-02 13:05 +0000
            Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 17:56 -0700
  Re: Reading beyond the end of file Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-09-11 13:55 -0600
    Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-26 14:14 -0700
      Re: Reading beyond the end of file Siri Cruz <chine.bleu@yahoo.com> - 2015-09-26 14:43 -0700
        Re: Reading beyond the end of file Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-09-26 17:57 -0400
        Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-01 14:01 -0700
      Re: Reading beyond the end of file Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-09-26 22:18 -0600
        Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-01 12:58 -0700
          Re: Reading beyond the end of file Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-10-01 15:08 -0600
            Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 18:03 -0700
              Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 04:02 +0000
      Re: Reading beyond the end of file raltbos@xs4all.nl (Richard Bos) - 2015-10-02 13:11 +0000
        Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-02 09:31 -0700
          Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-03 16:07 -0400
        Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 19:06 -0700
  Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-09-11 14:36 -0700
    Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-26 14:05 -0700
      Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-09-26 18:53 -0700
        Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-01 13:49 -0700
          Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-01 20:23 -0400
            Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-02 06:14 +0000
            Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-04 19:03 -0700
              Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-04 22:55 -0400
                Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 04:27 +0000
                Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-04 22:21 -0700
                Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 09:53 +0000
                Re: Reading beyond the end of file James Kuyper <jameskuyper@verizon.net> - 2015-10-05 13:15 -0400
                Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-05 10:25 -0700
                Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 21:30 +0000
                Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 21:27 +0000
                Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-05 10:17 -0700
                Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-05 11:59 -0700
                Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-05 13:44 -0700
                Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 21:58 +0000
                Ones' complement subtraction supercat@casperkitty.com - 2015-10-05 15:28 -0700
                Re: Ones' complement subtraction glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 02:14 +0000
                Re: Ones' complement subtraction supercat@casperkitty.com - 2015-10-06 08:48 -0700
                Re: Ones' complement subtraction glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 20:55 +0000
                Re: Ones' complement subtraction supercat@casperkitty.com - 2015-10-06 14:41 -0700
                Re: Ones' complement subtraction glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-07 00:14 +0000
                Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-05 15:24 -0700
                Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 21:39 +0000
                Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-05 15:31 -0700
                Re: Reading beyond the end of file glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 03:04 +0000
                Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-06 08:55 -0700
                Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-06 11:44 -0700
                Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-05 23:16 -0400
                Re: Reading beyond the end of file James Kuyper <jameskuyper@verizon.net> - 2015-10-06 10:29 -0400
                Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-06 08:56 -0700
                Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-06 23:13 -0400
                Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-06 22:01 -0700
                Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-07 08:43 -0700
                Re: Reading beyond the end of file supercat@casperkitty.com - 2015-10-07 10:02 -0700
                Re: Reading beyond the end of file Keith Thompson <kst-u@mib.org> - 2015-10-07 13:08 -0700
                Re: Reading beyond the end of file Richard Damon <Richard@Damon-Family.org> - 2015-10-07 22:03 -0400
                Re: Reading beyond the end of file Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-05 01:47 -0700

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