Re: pack it in

one of the little imps in my head just found the light switch. thank you :-) Nathan Nobbe schreef:

On Jan 24, 2008 7:13 PM, Jochem Maas <jochem@iamjochem.com <mailto:jochem@iamjochem.com>> wrote:

    ok. that's where my brain goes to mush - all strings in php (for now)
    are binary ... what's the difference between the binary strings
    in php and such found in these 'binary files' that they need to be
    packed/unpacked?

    sorry if I'm sounding retarded ... I probably am :-/

pack() allows you to format binary data. it can be formatted for specific architectures as well. formating of php stings does not take place on a binary level, rather it occurs on a byte level, or multibyte using the multibyte string functions http://www.php.net/manual/en/ref.mbstring.php <http://www.php.net/manual/en/ref.mbstring.php> here is a nice example i found from phpdig.net <http://phpdig.net>, that is designed to determine whether a system is little, big, or middle endian. (there is a small error on the script at the actual website; ive modified it for the post here and sent a notice to the site regarding it). id like to see how this could be done w/ regular php strings :) <?php # A hex number that may represent 'abyz' $abyz = 0x6162797A; # Convert $abyz to a binary string containing 32 bits # Do the conversion the way that the system architecture wants to switch (pack ('L', $abyz)) {

    # Compare the value to the same value converted in a Little-Endian fashion
    case pack ('V', $abyz):
        echo 'Your system is Little-Endian.';
        break;

    # Compare the value to the same value converted in a Big-Endian fashion
    case pack ('N', $abyz):
        echo 'Your system is Big-Endian.';
        break;

    default:
        $endian = "Your system 'endian' is unknown."
            . "It may be some perverse Middle-Endian architecture.";

} ?> -nathan