/**
* Compresses an IPv6 adress
*
* RFC 2373 allows you to compress zeros in an adress to '::'. This
* function expects an valid IPv6 adress and compresses successive zeros
* to '::'
*
* Example: FF01:0:0:0:0:0:0:101 -> FF01::101
* 0:0:0:0:0:0:0:1 -> ::1
*
* Whe $ip is an already compressed adress the methode returns the value as is,
* also if the adress can be compressed further.
*
* Example: FF01::0:1 -> FF01::0:1
*
* To enforce maximum compression, you can set the second argument $force to true.
*
* Example: FF01::0:1 -> FF01::1
*
* @param String $ip a valid IPv6-adress (hex format)
* @param boolean $force if true the adress will be compresses as best as possible (since 1.2.0)
*
* @return tring the compressed IPv6-adress (hex format)
* @access public
* @see Uncompress()
* @static
* @author elfrink at introweb dot nl
*/
public static function compress($ip, $force = false)
{
if (false !== strpos($ip, '::')) {
// its already compressed
if (true == $force) {
$ip = Net_IPv6::uncompress($ip);
} else {
return $ip;
}
}
$prefix = Net_IPv6::getPrefixLength($ip);
if (false === $prefix) {
$prefix = '';
} else {
$ip = Net_IPv6::removePrefixLength($ip);
$prefix = '/' . $prefix;
}
$netmask = Net_IPv6::getNetmaskSpec($ip);
$ip = Net_IPv6::removeNetmaskSpec($ip);
$ipp = explode(':', $ip);
for ($i = 0; $i < count($ipp); $i++) {
$ipp[$i] = dechex(hexdec($ipp[$i]));
}
$cip = ':' . join(':', $ipp) . ':';
preg_match_all("/(:0)(:0)+/", $cip, $zeros);
if (count($zeros[0]) > 0) {
$match = '';
foreach ($zeros[0] as $zero) {
if (strlen($zero) > strlen($match)) {
$match = $zero;
}
}
$cip = preg_replace('/' . $match . '/', ':', $cip, 1);
}
$cip = preg_replace('/((^:)|(:$))/', '', $cip);
$cip = preg_replace('/((^:)|(:$))/', '::', $cip);
if ('' != $netmask) {
$cip = $cip . '/' . $netmask;
}
return $cip . $prefix;
}