pfSense

/*

 * Convert an IPv4 or IPv6 IP range to an array of subnets which can contain the range.

 * Algorithm and embodying code PD'ed by Stilez - enjoy as you like :-)

 *

 * Documented on pfsense dev list 19-20 May 2013. Summary:

 *

 * The algorithm looks at patterns of 0's and 1's in the least significant bit(s), whether IPv4 or IPv6.

 * These are all that needs checking to identify a _guaranteed_ correct, minimal and optimal subnet array.

 *

 * As a result, string/binary pattern matching of the binary IP is very efficient. It uses just 2 pattern-matching rules

 * to chop off increasingly larger subnets at both ends that can't be part of larger subnets, until nothing's left.

 *

 * (a) If any range has EITHER low bit 1 (in startip) or 0 (in endip), that end-point is _always guaranteed_ to be optimally

 * represented by its own 'single IP' CIDR; the remaining range then shrinks by one IP up or down, causing the new end-point's

 * low bit to change from 1->0 (startip) or 0->1 (endip). Only one edge case needs checking: if a range contains exactly 2

 * adjacent IPs of this format, then the two IPs themselves are required to span it, and we're done.

 * Once this rule is applied, the remaining range is _guaranteed_ to end in 0's and 1's so rule (b) can now be used, and its

 * low bits can now be ignored.

 *

 * (b) If any range has BOTH startip and endip ending in some number of 0's and 1's respectively, these low bits can

 * *always* be ignored and "bit-shifted" for subnet spanning. So provided we remember the bits we've place-shifted, we can

 * _always_ right-shift and chop off those bits, leaving a smaller range that has EITHER startip ending in 1 or endip ending

 * in 0 (ie can now apply (a) again) or the entire range has vanished and we're done.

 * We then loop to redo (a) again on the remaining (place shifted) range until after a few loops, the remaining (place shifted)

 * range 'vanishes' by meeting the exit criteria of (a) or (b), and we're done.

 */

	$replace = array(

	    '/', '-', ' ', '!', '@', '#', '$', '%', '^', '&', '*', '(', ')',

	    '_', '+', '=', '{', '}', '[', ']', '|', '/', '<', '>', '?',

	    ':', ',', '.', '\'', '\\'

	);

		$value = str_pad($value, 2, '0', STR_PAD_LEFT);

	if(!is_duid($duidstring)) {

function get_duid_from_file() {

			$buffer = fread($fd,16);

	return($duid_ASCII);