in reply to CRC of a string

See the  % template field prefix of unpack (search for '%' or 'prefix'): 
>perl -wMstrict -le
"my $str = '/etc/test2.sh';
 $str .= qq{\0\0\0};
 print unpack '%32N*', $str;
"
990644297

[download]
(See pack for full documentation of template field specifiers, e.g., 'N', 'n', 'V', 'v', etc.)

Updates:

Replies are listed 'Best First'.
Re^2: CRC of a string
by keszler (Priest) on Nov 18, 2009 at 20:07 UTC
    Interesting! Your code works for me, with the same result, but when I try 
    perldoc -f pack | grep %

    [download]

    I get only 3 lines - the same three as found searching for '%' in pack - none of which mention the use of '%' in the (un)pack template.

[reply]
[d/l]
      Right you are. My memory failed me. It is discussed in unpack and seems to be referred to as a 'template field prefix'. Search for '%' or 'prefix'. Reply fixed.
[reply]

        Thank you very much for your great answers. So I could learn a lot.

        Here the final solution: 

        #!/usr/bin/perl

use strict;
use warnings;

my $str = "/etc/test2.sh"; # checksum32: 990644297
my $checksum32 = &calcChecksum32($str);

print $checksum32 . "\n";

sub calcChecksum32()
{
    my $str = $_[0];
    my $nb_pad_bytes = 4 - (length($str) % 4);

    $str .= "\0" x $nb_pad_bytes;
    unpack('%32N*', $str);
}

        [download]
[reply]
[d/l]

In Section Seekers of Perl Wisdom