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Groups > comp.lang.c > #15396

Re: Small Variant Records in C

From jgk@panix.com (Joe keane)
Newsgroups comp.lang.c
Subject Re: Small Variant Records in C
Date 2012-01-04 03:52 +0000
Organization Public Access Networks Corp.
Message-ID <je0ieo$4mq$1@reader1.panix.com> (permalink)
References <126812ae-e278-4572-900f-6068c7fd89ff@d17g2000yql.googlegroups.com> <slrnjeslun.8g9.usenet-nospam@guild.seebs.net> <b31838b4-399d-452e-9531-9fa92b5d09db@m10g2000vbc.googlegroups.com> <jcm7d3$e0s$1@dont-email.me>

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In article <jcm7d3$e0s$1@dont-email.me>, BartC <bc@freeuk.com> wrote:
>How important is it to have the minimum number (of bytes usually rather than 
>bits)?

supposing that you *know* the subclasses

e.g.

class Foo
{
    int foo_common;
}

class RedFoo : Foo
{
    char redbit;
}

class GreenFoo : Foo
{
    double greenvalue;
}

struct bluefooextra { ... };

class BlueFoo : Foo
{
    struct bluefooextra *blueextra;
}

[and there aren't any purple or oranges foos]

class AllFoos
{
    union {struct RedFoo af_r; struct GreenFoo af_g; struct BlueFoo af_b;} y;
}

typedef class AllFoos *CanHoldAnyFoo;

int f(...)
{
    ...
    CanHoldAnyFoo x;

    x = malloc(len * sizeof(AllFoos));
    if (x = NULL)
	do_something();
    ...
}

then it may be useful

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Thread

Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-18 10:16 -0800
  Re: Small Variant Records in C Seebs <usenet-nospam@seebs.net> - 2011-12-18 18:50 +0000
    Re: Small Variant Records in C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-18 15:00 -0500
      Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-18 12:23 -0800
        Re: Small Variant Records in C Seebs <usenet-nospam@seebs.net> - 2011-12-18 21:15 +0000
          Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-18 14:13 -0800
            Re: Small Variant Records in C Seebs <usenet-nospam@seebs.net> - 2011-12-19 00:26 +0000
            Re: Small Variant Records in C "BartC" <bc@freeuk.com> - 2011-12-19 02:25 +0000
              Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-18 19:08 -0800
                Re: Small Variant Records in C "BartC" <bc@freeuk.com> - 2011-12-19 17:24 +0000
                Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-19 11:43 -0800
                Re: Small Variant Records in C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-19 15:21 -0500
                Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-19 13:38 -0800
                Re: Small Variant Records in C James Kuyper <jameskuyper@verizon.net> - 2011-12-19 16:48 -0500
                Re: Small Variant Records in C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-19 17:19 -0500
                Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-19 15:14 -0800
                Re: Small Variant Records in C "BartC" <bc@freeuk.com> - 2011-12-19 21:44 +0000
                Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-19 14:02 -0800
                Re: Small Variant Records in C Kaz Kylheku <kaz@kylheku.com> - 2011-12-19 18:38 +0000
              Re: Small Variant Records in C jgk@panix.com (Joe keane) - 2012-01-04 03:52 +0000
                Re: Small Variant Records in C Ian Collins <ian-news@hotmail.com> - 2012-01-04 20:25 +1300
          Re: Small Variant Records in C Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 15:53 -0800
        Re: Small Variant Records in C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-18 18:35 -0500
          Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-18 16:01 -0800
            Re: Small Variant Records in C Seebs <usenet-nospam@seebs.net> - 2011-12-19 00:26 +0000
              Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-18 17:02 -0800
            Re: Small Variant Records in C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-18 19:53 -0500
              Re: Small Variant Records in C "BartC" <bc@freeuk.com> - 2011-12-19 01:36 +0000
                Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-18 18:21 -0800
                Re: Small Variant Records in C "BartC" <bc@freeuk.com> - 2011-12-19 02:52 +0000
                Re: Small Variant Records in C Marco Devillers <marco.devillers@gmail.com> - 2011-12-18 19:17 -0800
                Re: Small Variant Records in C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-19 09:24 -0500
                Re: Small Variant Records in C "BartC" <bc@freeuk.com> - 2011-12-19 17:18 +0000

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