update:

#!/usr/bin/perl -w
use C::Include;
use strict;
use vars qw/$inc $send $buffer/;

$inc = new C::Include( \*DATA );

# Make struct instance
$send = $inc->make_struct('send');
use Data::Dumper;
print Dumper $send;

# Fill struct fields
$$send{prevpass} = '0123456789';
$$send{answer} = 1;

# Pack struct to buffer
$buffer = $send->pack();

# Struct size
printf "Size of struct send: %d bytes\n",   $send->size;
printf "Size of unsigned long: %d bytes\n", $inc->sizeof('unsigned lon
+g');

# Print buffer to STDOUT
&hview( \$buffer );

#require 'hview.pl';
## crazyinsomniac's note ~ hview.pl is distributed with the module, pr
+ops to the author
sub hview(\$){
    my $str = shift;
    my @lines = unpack 'a16'x(length($$str)/16+(length($$str)%16?1:0))
+, $$str;

    for( 0..$#lines ){
        printf "%08X:  %-17sł %-17s  %-16s\n", $_*16,
            (map{
                sprintf '%-2s ' x 8, map{
                    sprintf'%02X',$_
                }unpack 'C*', $_
            }unpack 'a8a8', $lines[$_]),
            $lines[$_];
    }
}
1;

__END__
#define PORT 2345
#define CHALLENGE 0
#define CORRECT 1
#define WRONG 2

struct recv {
    int flag;
    int b[4];
    char nextpass[10];
};

typedef struct recv t_recv;

struct send {
    int answer;
    char prevpass[10];
};
typedef struct send t_send;
[download]

$>perl test4.pl
$VAR1 = bless( {
                 '' => {
                         'length' => 14,
                         'mask' => 'iZ10',
                         'tag' => 'send',
                         'buffers' => [
                                        \undef,
                                        \undef
                                      ]
                       },
                 'prevpass' => ${$VAR1->{''}{'buffers'}[1]},
                 'answer' => ${$VAR1->{''}{'buffers'}[0]}
               }, 'C::Include::Struct' );
Size of struct send: 14 bytes
Size of unsigned long: 4 bytes
00000000:  01 00 00 00 30 31 32 33 ¦ 34 35 36 37 38 00         
   012
+345678

$>
[download]

I tried $VERSION = 1.20;, but It didn't like your macro (WARNING: Unashed code ...) so I upgraded ... and all this after plenty of rum and coke (and some Jose Quervo tequila to boot)

 

______crazyinsomniac_____________________________ Of all the things I've lost, I miss my mind the most. perl -e "$q=$_;map({chr unpack qq;H*;,$_}split(q;;,q*H*));print;$q/$q;"

There may also be an example in the proposed perlpacktut that's been floating around the perl 5 porters mailing list.

  my ($flag, $b1, $b2, $b3, $b4, $nextpass) =
    unpack ( "iiiiiZ*", $received_binary_struct );
 
  my $binary_struct_to_send = 
    pack ( "iZ*", $answer, $prevpass );
[download]

#!/usr/bin/perl -w

use Inline C;
use strict; $|++;

my $recv = test_recv_struct();
print "recv: " . join ( ",", unpack ( "iiiiiZ*", $recv ) ) . "\n";

my $send = pack ( "iZ*", 1, "string two" );
test_send_struct ( $send );

__END__
__C__

struct recv {
  int flag;
  int b[4];
  char nextpass[10];
};
typedef struct recv t_recv;

struct send {
  int answer;
  char prevpass[10];
};
typedef struct send t_send;

//-----

SV* test_recv_struct() {
  t_recv* foo = malloc ( sizeof(t_recv) );
  foo->flag = 1;
  foo->b[0] = 2;
  foo->b[1] = 3;
  foo->b[2] = 4;
  foo->b[3] = 5;
  sprintf( foo->nextpass, "a string" );
  return newSVpv ( (char*)foo, sizeof(t_recv) );
}

void test_send_struct ( char* perl_packed ) {
  t_send* foo = perl_packed;
  printf ( "send: %d,%s\n", foo->answer, foo->prevpass );
}
[download]

Inline is really nifty!

Inline::Struct is an extension to Inline::C which does exactly what you want.

After Compline,
Zaxo

I'm not sure Inline::Struct does do the right thing, here. Inline::Struct provides a simple way to manipulate a a C struct as a Perl object (which is very often exactly what one needs to do in the context of writing a bunch of Inline::C code). But AFAICT there are no documented methods for reading in a C struct from a blob of bytes or for dumping one out.

That's exactly what pack and unpack are for.

Having said that, it's probably worth writing to the Inline mailing list and suggesting such an addition to the API.

Kwin