Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #18520

Re: What is the right way to do this simple thing

Show all headers | View raw

On 03/11/12 05:46 PM, Richard Harter wrote:
> On Sun, 11 Mar 2012 14:15:52 +1300, Ian Collins<ian-news@hotmail.com>
> wrote:
>
>> On 03/11/12 01:44 PM, Richard Harter wrote:
>>> On Sun, 11 Mar 2012 13:06:18 +1300, Ian Collins<ian-news@hotmail.com>
>>> wrote:
>>>>
>>>> Why don't you just use the usual union in a struct technique?
>>>
>>> You might spell out what you think "the usual"  is; I looked at
>>> several variations and it looked like there were subtle problems with
>>> all of them.  Perhaps I missed something.
>>
>> struct load_package {
>>    message_type type;       /* The type has access info    */
>>    size_t       total_len;  /* Total length of the package */
>>    size_t       data_len;   /* Length of the data          */
>>    union {
>>      payload_type1;
>>      payload_type2;
>>    } payload;
>> };
>
> Unless you have something in mind that I'm missing this won't do at
> all.  First of all there is no guarantee of alignment - there may have
> to be padding between data_len and the union.

So?  Using a union solves the alignment issue - it will be correctly 
aligned.

> Secondly I really hope
> you aren't suggesting that every different payload type in a program
> must be in that union.

Well that depends on the relationship between the types.  If they are 
related, why not?  The X11 Event structure has a couple of dozen or so 
structs in its union member.

> The point of the second bit of code that I did is that it does take
> care of alignment and doesn't drag in stuff from all other
> serializations.

?

-- 
Ian Collins

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-10 19:26 +0000
  Re: What is the right way to do this simple thing Don Y <this@isnotme.com> - 2012-03-10 12:57 -0700
  Re: What is the right way to do this simple thing ImpalerCore <jadill33@gmail.com> - 2012-03-10 14:12 -0800
    Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-10 23:31 +0000
      Re: What is the right way to do this simple thing Ian Collins <ian-news@hotmail.com> - 2012-03-11 13:06 +1300
        Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 00:44 +0000
          Re: What is the right way to do this simple thing Ian Collins <ian-news@hotmail.com> - 2012-03-11 14:15 +1300
            Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 04:46 +0000
              Re: What is the right way to do this simple thing Ian Collins <ian-news@hotmail.com> - 2012-03-11 21:27 +1300
                Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 17:23 +0000
                Re: What is the right way to do this simple thing Ian Collins <ian-news@hotmail.com> - 2012-03-12 10:01 +1300
                Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-13 21:18 +0000
                Re: What is the right way to do this simple thing Ian Collins <ian-news@hotmail.com> - 2012-03-14 10:23 +1300
              Re: What is the right way to do this simple thing Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-11 11:59 +0000
                Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 16:51 +0000
                Re: What is the right way to do this simple thing Gene <gene.ressler@gmail.com> - 2012-03-13 07:32 -0700
                Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-13 21:46 +0000
      Re: What is the right way to do this simple thing ImpalerCore <jadill33@gmail.com> - 2012-03-12 07:28 -0700
        Re: What is the right way to do this simple thing ImpalerCore <jadill33@gmail.com> - 2012-03-12 08:13 -0700
        Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-13 21:51 +0000
  Re: What is the right way to do this simple thing Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-10 14:21 -0800
    Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 01:40 +0000
      Re: What is the right way to do this simple thing Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-11 14:11 -0700
        Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-13 21:56 +0000
          Re: What is the right way to do this simple thing Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-14 14:55 -0700
            Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-15 21:55 +0000
              Re: What is the right way to do this simple thing Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-19 13:33 -0700
  Re: What is the right way to do this simple thing Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-10 15:21 -0800
    Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 00:47 +0000
  Re: What is the right way to do this simple thing Philip Lantz <prl@canterey.us> - 2012-03-11 01:07 -0800
    Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 16:14 +0000
  Re: What is the right way to do this simple thing Markus Wichmann <nullplan@gmx.net> - 2012-03-11 13:47 +0100
    Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 16:24 +0000
  Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 21:01 +0000
    Re: What is the right way to do this simple thing Anders Wegge Keller <wegge@wegge.dk> - 2012-03-12 00:05 +0100
      Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-13 21:57 +0000
    Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-11 23:06 +0000
      Re: What is the right way to do this simple thing Geoff <geoff@invalid.invalid> - 2012-03-11 17:34 -0700
        Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-13 22:00 +0000
          Re: What is the right way to do this simple thing Geoff <geoff@invalid.invalid> - 2012-03-13 18:12 -0700
            Re: What is the right way to do this simple thing cri@tiac.net (Richard Harter) - 2012-03-14 03:38 +0000
              Re: What is the right way to do this simple thing Geoff <geoff@invalid.invalid> - 2012-03-14 00:49 -0700

csiph-web