note 105083 deleted from function.ip2long by danbrown
| From: | danbrown@php.net | Date: | Tue, 26 Jul 2011 21:42:17 +0000 |
| Subject: | note 105083 deleted from function.ip2long by danbrown | ||
| References: | 1 | Groups: | php.notes |
| Request: | Send a blank email to php-notes+get-181923@lists.php.net to get a copy of this message | ||
Note Submitter: contact at nullivex dot com
----
This is an improvement on an existing function submitted on this list which I have added below.
Improved function
---------
<?php
//with static magic number
function mask2cidr($mask){
return 32 - intval(log(4294967296 - ip2long($mask),2));
}
//with bit shifted net size
function mask2cidr($mask){
return 32 - intval(log((1<<32) - ip2long($mask),2));
}
//constant
define('MAX_NETSIZE',4294967296);
function mask2cidr($mask){
return 32 - intval(log(MAX_NETSIZE - ip2long($mask),2));
}
/*
Preferred method is a constant with a magic number.
Using the least amount of memory and CPU cycles along
with greatest readability.
---
The first two functions work great standalone though.
*/
?>
Original Method
---------------------------------------
A quick method to convert a netmask (ex: 255.255.255.240) to a cidr mask (ex: /28):
<?php
function mask2cidr($mask){
$long = ip2long($mask);
$base = ip2long('255.255.255.255');
return 32-log(($long ^ $base)+1,2);
/* xor-ing will give you the inverse mask,
log base 2 of that +1 will return the number
of bits that are off in the mask and subtracting
from 32 gets you the cidr notation */
}
?>