Packing struct timeval

[zwon]

I used to set timeout on socket with the following code:

my $timeout = pack( 'L!L!', $seconds, 0 );
defined $socket->sockopt( SO_RCVTIMEO, $timeout )
  or die "Couldn't set timeout: $!";

And it worked just fine till they released NetBSD 6.0. It uses 64-bit time_t on all architectures, so I'm getting failures from cpan testers for NetBSD 6.0 on i386. Now I'm looking for a new elegant way to pack timeval. I can easily do it in C:

use 5.010;
use strict;
use warnings;

use Inline C => 'DATA';

my $timeval = pack_timeval(2,0);

__DATA__
__C__

SV* pack_timeval(time_t tv_sec, long tv_usec) {
    struct timeval tv;

    tv.tv_sec = tv_sec;
    tv.tv_usec = tv_usec;
    return newSVpv((char *) &tv, sizeof(struct timeval));
}

But I don't see any way to get size of time_t using pure Perl, it seems Config doesn't provide this parameter.

[Anonymous Monk]

$ perl -V:timeincl -V:timetype
timeincl='/usr/include/sys/time.h ';
timetype='time_t';

Then maybe Convert::Binary::C can help ... much easier to abandon pure-perl :)

[zwon]

Thank you, that's definitely interesting, but not exactly suit my taste ;) I tried to make a quick example with it and failed. First, my timeincl contains two files:

$ perl -V:timeincl
timeincl='/usr/include/x86_64-linux-gnu/sys/time.h /usr/include/time.h
+ ';

Second, it seems not that easy to make it parse time.h, you may have to add some include directories and define some macros, depending on the system, so it is not that portable. I stopped with this:

use 5.010;
use strict;
use warnings;

use Convert::Binary::C;
use Config;

my $c = Convert::Binary::C->new;
$c->Include(
    '/usr/include',
    '/usr/include/x86_64-linux-gnu/sys/',
    '/usr/include/x86_64-linux-gnu/'
)->Define('__WORDSIZE=64');
$c->parse_file('/usr/include/x86_64-linux-gnu/sys/time.h');
my $timeval = $c->pack( 'struct timeval', { tv_sec => 1, tv_usec => 0 
+} );

And it gave me

bits/wordsize.h, line 7: macro '__WORDSIZE' redefined unidentically
    included from /usr/include/x86_64-linux-gnu//sys/cdefs.h:378
    included from /usr/include/features.h:357
    included from /usr/include/x86_64-linux-gnu/sys/time.h:23 at pack_
+timeval2.pl line 10.

I probably would be able to make it work on my particular system, but not in general case. And it requires that includes were installed on a target system, which may not be the case.

[Anonymous Monk]

I tried to make a quick example with it and failed.

I kinda knew it would -- reinventing a compiler is hard -- it much simpler to compile a c program to dump the structure of struct, kinda sorta the trick C::DynaLib::Struct/hparse employs

I suppose you could always "fingerprint an os" and build a database of time formats ... pure-perl is pure insanity if you ask me, much less work to install a compiler :)