UUID v5 not universal?

[elmimmo]

Using class.uuid.php to generate UUID v5 I do not get the same result as using OSSP UUID, with same namespace and name.

Using OSSP UUID like this:

uuid -v5 ns:DNS www.widgets.com

or this:

uuid -v5 6ba7b810-9dad-11d1-80b4-00c04fd430c8 www.widgets.com

gives me 21f7f8de-8051-5b89-8680-0195ef798b6a.

class.uuid.php gives me 13726f09-44a9-5eeb-8910-3525a23fb23b instead.

Am I not supposed to get the same UUID no matter the implementation, given the same namespace and name?

[elmimmo]

I do get the same result as OSSP UUID with this other UUID generator implementation in PHP by Andrew Moore, so I assume UUID v5 generation in class.uuid.php is broken.

Can someone please confirm?

[dolfs]

The problem is the use of the swap functions that are not needed if your platform is little endian. With the modifications below it produces the same results in all cases. The mods introduce an endian-ness check, a method to only check once after the class is loaded. Due to the static methods only nature of this class, the two public API functions will need to call the define method every time (no code can be executed at class load times without tricks). Note also that the public API methods contained a bug which would throw warnings in some cases. That has been fixed as well.

    private static $m_isBigEndian;

    private static function defineEndian() {
        if (!isset(self::$m_isBigEndian)) {
            // A hex number that may represent 'abyz'
            $abyz = 0x6162797A;
            /**
             * Convert the hext value to a binary string (32 bits) using
             * the 'L' option (which does a machine dependent conversion).
             * Then compare with a specific endian conversion to determine what
             * kind of machine we have.
             */
            self::$m_isBigEndian = pack('L', $abyz) == pack('N', $abyz);
        }
    }

    /* Swap byte order of a 32-bit number */
    private static function swap32($x) {
        if (!self::$m_isBigEndian) {
            return $x;
        }
        return (($x & 0x000000ff) << 24) | (($x & 0x0000ff00) << 8) |
                (($x & 0x00ff0000) >> 8) | (($x & 0xff000000) >> 24);
    }

    /* Swap byte order of a 16-bit number */
    private static function swap16($x) {
        if (!self::$m_isBigEndian) {
            return $x;
        }
        return (($x & 0x00ff) << 8) | (($x & 0xff00) >> 8);
    }

    /*
     * Public API, generate a UUID of 'type' in format 'fmt' for
     * the given namespace 'ns' and node 'node'
     */
    public static function generate($type, $fmt = self::FMT_BYTE, $node = '', $ns = '') {
        if (!isset(self::$m_generate[$type]))
            return null;
        self::defineEndian();
        $func = self::$m_generate[$type];
        return self::convert(self::$func($ns, $node), self::FMT_FIELD, $fmt);
    }

    /*
     * Public API, convert a UUID from one format to another
     */
    public static function convert($uuid, $from, $to) {
        if (!isset(self::$m_convert[$from][$to]))
            return $uuid;

        self::defineEndian();
        $conv = self::$m_convert[$from][$to];
        return self::$conv($uuid);
    }