[PHP] ip addresses and ip prefixes

<?php /**
* input $limits array or yii object of IP addresses sorted by SQL server
* returns array of aggregated prefixes and netmask lengths (aka masklen)
*/ function _viewAggregate($limits) { // input addresses must be sorted ascending
    $input = $output = array();
    $index = 0;
    foreach( $limits as $l ) { // fix pure IPs without prefix, prepare array of prefixes
        $n = explode ("/",$l->address, 1);
        if (empty($n[1])) // optionally fix host mask = /32
            $n[1] = 32;
        $net['prefix'] = $n[0];
        $net['masklen'] = $n[1];
        $net['version'] = (8*strlen($net['prefix']) == 128 ) ? 6 : 4; // detect IP prefix version (6 or 4)
        $net['index'] = $index;
        $input[$index++] = $net; // pure array of prefixes with extra info
    }
    $reductions = 1; $iteration = 0;
    while($reductions > 0) {
        $iteration++;
        $reductions = $skipNext = 0;
        $output = array();
        foreach( array_keys($input) as $key ) {
            if ($skipNext) {
                $skipNext = false;
                continue;
            }
            $i = $input[$key];
            $prefixWithoutMask = ($i['version']==4) ? ip2long($i['prefix']) >> (32-$i['masklen']) : ip2long6($i['prefix']) >> (128-$i['masklen']);
            if (!empty($input[1+$key])) {
                $next = $input[1+$key];
            } else continue; // skip the last element
            $nextPrefixWithoutMask = ($next['version']==4) ? ip2long($next['prefix']) >> (32-$next['masklen']) : ip2long6($next['prefix']) >> (128-$next['masklen']);
            if ( ($i['masklen'] == $next['masklen']) // neighbouring prefixes are of the same length
                AND ($nextPrefixWithoutMask - $prefixWithoutMask === 1) // prefixes differ by 1 in the last digit
                AND (($prefixWithoutMask >> 1) === ($nextPrefixWithoutMask >> 1)) ) { // higher bits are equal
                $i['masklen']--; // aggregate with the next record
                $skipNext = true;
                $reductions++;
            }
            $output[] = $i;
        }
        $input = array_merge(array(), $output); // renumber the array index/key
    }
    return $input;
}

function _viewMaskLengthToMask($len) { // ipv4 only
     if ($len <= 32)
        return long2ip(((1 << (32-$len)) - 1));
}

function ip2long6($ipv6) {
  $ip_n = inet_pton($ipv6);
  $bits = 15; // 16 x 8 bit = 128bit
  while ($bits >= 0) {
    $bin = sprintf("%08b",(ord($ip_n[$bits])));
    $ipv6long = $bin.$ipv6long;
    $bits--;
  }
  return gmp_strval(gmp_init($ipv6long,2),10);
}

function long2ip6($ipv6long) {

  $bin = gmp_strval(gmp_init($ipv6long,10),2);
  if (strlen($bin) < 128) {
    $pad = 128 - strlen($bin);
    for ($i = 1; $i <= $pad; $i++) {
    $bin = "0".$bin;
    }
  }
  $bits = 0;
  while ($bits <= 7) {
    $bin_part = substr($bin,($bits*16),16);
    $ipv6 .= dechex(bindec($bin_part)).":";
    $bits++;
  }
  // compress

  return inet_ntop(inet_pton(substr($ipv6,0,-1)));
}