Hi Eric,
On 2012-11-13 Eric Norum wrote:
> So how does the author of a client (aSub subroutine or anything else)
> determine the meaning of NORD with the proposed change in place? How does
> the author determine whether the the source of a an array of characters is
> something that appends a nil or something like a serial/network port that
> does not?
Here's what my original statement said:
> I recommend (but we don't require) that anything generating a long string
> should add a Nil ('\0') terminator byte after the last character and count
> that in the number of elements reported for the array (e.g. when setting the
> waveform record's NORD field).
>
> However clients that read an array as a long string MUST be able to properly
> handle one that doesn't have a Nil terminator, and should not report an
> error in this case. The simplest way to ensure proper termination is to
> check if the byte at [len-1] is zero and if not append one (making sure you
> reserved space in your buffer for it). Maybe the source might even change
> at run time.
A generic client MUST properly handle an un-terminated string.
However someone writing a 1-off aSub subroutine for a 24-hour experiment to
run tomorrow who knows that their long string input value includes the Nil can
skip the additional step of terminating it and pass it straight to sprintf().
I'm trying to make it so that someone who knows nothing about this whole topic
and assumes that long strings follow the C standard can write a subroutine
that Just Works™ more often than it doesn't. Robust APIs are better than
brittle ones, and counting the Nil increases robustness.
> Mucking with the semantics of NORD is a BadIdea (™, IMHO).
This doesn't change the semantics of NORD at all which still tells you how
many elements there are in the array. I'm merely advocating that where the
data being put in the buffer is a Nil-terminated string, that the Nil byte
should be regarded as part of the string (following the C standard) and
included in the element count.
- Andrew
--
READ CAREFULLY. By reading this email, you agree, on behalf of your
employer, to release me from all obligations and waivers arising from
any and all NON-NEGOTIATED agreements, licenses, terms-of-service,
shrink-wrap, click-wrap, browse-wrap, confidentiality, non-disclosure,
non-compete and acceptable use policies ("BOGUS AGREEMENTS") that I
have entered into with your employer, its partners, licensors, agents
and assigns, in perpetuity, without prejudice to my ongoing rights
and privileges. You further represent that you have the authority to
release me from any BOGUS AGREEMENTS on behalf of your employer.
- Replies:
- Re: Long string support in CA clients and device support Eric Norum
- References:
- Long string support in CA clients and device support Andrew Johnson
- Re: Long string support in CA clients and device support Andrew Johnson
- Re: Long string support in CA clients and device support Eric Norum
- Navigate by Date:
- Prev:
Re: Long string support in CA clients and device support Eric Norum
- Next:
RE: Long string support in CA clients and device support Mark Rivers
- Index:
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
<2012>
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
- Navigate by Thread:
- Prev:
Re: Long string support in CA clients and device support Eric Norum
- Next:
Re: Long string support in CA clients and device support Eric Norum
- Index:
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
<2012>
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
|