Hi,
I'd like some help from anyone who can explain how the following pack/unpack examples work (in simple terms please :-) ).
All the examples I've looked at on the web mention the B32 format only briefly, use binary representation instead of decimal (as used by this prog) and only have 1 value after the 'B32, instead of 2 values as below.
The code below is based on a program I need to amend. I'd also like to know why the 2 different ways of retrieving the mask both work/produce the same answer.
Thanks for any help
Cheers
Chris
#!/usr/bin/perl -w
                                                                      
+          
use IO::Socket;
use strict;
                                                                      
+          
my (
    $key, %new,
    $str1, $str2, $str3,
    $mask, $ip, $ip_disp, $mask_disp
    );
                                                                      
+          
$str1 = '202.6.145.136';
$str2 = '29';
$str3 = '29';
print "$str1, $str2, $str3\n";
$mask = pack ('B32', (1 x $str2), (1 x (32 - $str2)));
$new {AA} {inet_aton ($str1) & $mask} =
                    $mask . pack ('B32', (1 x $str3), (1 x (32 - $str3
+)));
                                                                      
+          
for $ip ( keys %{$new{AA}} )
{
    $ip_disp = join('.',unpack('CCCC',$ip));
    print "unpack ip CCCC = $ip_disp\n\n";
                                                                      
+          
    $mask_disp = join('.',unpack('CCCC',$new{AA}{$ip}));
    print "unpack mask CCCC = $mask_disp\n\n";
                                                                      
+          
    $mask_disp = join('.',unpack('CCCC',substr($new{AA}->{$ip},0,4)));
    print "substr/unpack CCCC mask = $mask_disp\n";
}
exit;

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In reply to Pack/Unpack with B32 and related query by Anonymous Monk

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