Programming

I’m wondering for an hour, why the frig I’m getting missmatched checksums…. then it hit me, and I feel like punching myself in the head lol.

I tried this:

sub checksum {
    my $file = shift || return;

    my $md5 = Digest->new("MD5");
    my $sha = Digest->new("SHA-256");
    open my $fh, $file or die "Can't checksum file: $!";
    binmode($fh);

    return ( MD5     => $md5->addfile($fh)->hexdigest();
             SHA256  => $sha->addfile($fh)->hexdigest();
           );
}

and then compared the output agaisnt checksums generated by FreeBSDs md5/sha256 utilities (they are actually the same program). The MD5 matched perfectly, but the SHA256 were different.

After much thinking, I figured it out….

sub checksum {
    my $file = shift || return;

    my $md5 = Digest->new("MD5");
    my $sha = Digest->new("SHA-256");
    open my $fh, $file or die "Can't checksum file: $!";
    binmode($fh);
    my $mh = $md5->addfile($fh)->hexdigest();
    seek($fh, 0, 0); # <----- you've got to rewind it to the start of the file before the next I/O
    my $sh = $sha->addfile($fh)->hexdigest();
    return ( MD5     => $mh,
             SHA256  => $sh,
           );
}

The thing that really irks me, I was wondering if the Digest:: classes would be so nice, as to rewind the file handle when they were done, but I think that idea occured to me about 4 hours ago, lool. Actually, if I’ve got to rewind the fscking handle between objects, I may as well just walk the file and append the data to each as we go… then get the digests.

I really need more sleep….

EDIT: Take III

=pod internal

checksum FILENAME

Open filename, and return a hash containing ALGORITHM => check sum
key/value pairs, for each algorithm supported. Both MD5 and SHA256 will
always be supported.

=cut

sub checksum($) {
    my $file = shift || return;

    my $md5 = Digest->new("MD5");
    my $sha = Digest->new("SHA-256");
    open my $fh, $file         or die "Can't checksum file: $!";
    binmode($fh);

    # suck the file,  and Digest::add it. We would have to parse 
    # the entire file per object, and seek to 0,0 between calls other wise.
    while (my $ln = <$fh>) {
        $md5->add($ln);
        $sha->add($ln);
    }
    close $fh;

    return ( MD5     => $md5->hexdigest(),
             SHA256  => $sha->hexdigest(),
           );
}

instead of writing the file path, and using tab completion to view a file listed in a programs output: you pipe the programs output into a command to get the desired line, pipe then pipe that into AWK, so you can pipe that into xargs ….

or maybe it’s just being lazy….

Terry@dixie$ perl script-name project --debug | head -n 1 | awk '{ print $2 }' | xargs cat