As always TIMTOWTDI, but personally I'd implement it as if I was reading a stream, i.e. with read. Either you give each class the ability to parse the binary representation of itself, or you implement the reading as a single function that just constructs objects of the corresponding class (this would make it easier if the sections aren't entirely independent of each other, like if you've got a checksum over multiple sections). I've chosen the latter here:

use warnings;
use 5.012; # for "package BLOCK" syntax

package MainHeader {
    use Moo;
    has foo => ( is => 'ro' );
}
package ExtHeader {
    use Moo;
    has bar => ( is => 'ro' );
}
package Section {
    use Moo;
    has type => ( is => 'ro' );
    has quz => ( is => 'ro' );
}

my $binfile =
     "\x01\x06Hello\0"
    ."\x02\x04\0\x12\x34\x56"
    ."\x13\x02\xBE\xEF";

sub binread { # helper function for read+unpack
    my ($fh, $bytes, $templ) = @_;
    read($fh, my $data, $bytes) == $bytes
        or die "failed to read $bytes bytes";
    return unpack($templ, $data);
}

open my $fh, '<:raw', \$binfile or die $!;
my @packets;
while (!eof($fh)) {
    my ($type, $length) = binread($fh, 2, "CC");
    if ($type == 0x01) {
        my ($foo) = binread($fh, $length, 'Z*');
        my $hdr = MainHeader->new( foo => $foo );
        push @packets, $hdr;
    }
    elsif ($type == 0x02) {
        my ($bar) = binread($fh, $length, 'N');
        my $exthdr = ExtHeader->new( bar => $bar );
        push @packets, $exthdr;
    }
    elsif ($type == 0x13) {
        my ($quz) = binread($fh, $length, 'n');
        my $sect = Section->new( type => $type, quz => $quz );
        push @packets, $sect;
    }
    else { die "Unknown packet type $type" }
}
close $fh;

use Data::Dump;
dd @packets;
__END__
(
  bless({ foo => "Hello" }, "MainHeader"),
  bless({ bar => 1193046 }, "ExtHeader"),
  bless({ quz => 48879, type => 19 }, "Section"),
)

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In reply to Re: Best way to a parse a big binary file by haukex
in thread Best way to a parse a big binary file by Dirk80

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