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<?php
/* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */
/**
* DNS Library for handling lookups and updates.
*
* PHP Version 5
*
* Copyright (c) 2010, Mike Pultz <mike@mikepultz.com>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* * Neither the name of Mike Pultz nor the names of his contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRIC
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* @category Networking
* @package Net_DNS2
* @author Mike Pultz <mike@mikepultz.com>
* @copyright 2010 Mike Pultz <mike@mikepultz.com>
* @license http://www.opensource.org/licenses/bsd-license.php BSD License
* @version SVN: $Id$
* @link http://pear.php.net/package/Net_DNS2
* @since File available since Release 1.1.0
*
*/
/**
* A class to provide simple dns lookup caching.
*
* @category Networking
* @package Net_DNS2
* @author Mike Pultz <mike@mikepultz.com>
* @license http://www.opensource.org/licenses/bsd-license.php BSD License
* @link http://pear.php.net/package/Net_DNS2
* @see Net_DNS2_Packet
*
*/
class Net_DNS2_Cache
{
/*
* the filename of the cache file
*/
protected $cache_file = '';
/*
* the local data store for the cache
*/
protected $cache_data = array();
/*
* the size of the cache to use
*/
protected $cache_size = 0;
/*
* the cache serializer
*/
protected $cache_serializer;
/*
* an internal flag to make sure we don't load the cache content more
* than once per instance.
*/
protected $cache_opened = false;
/**
* returns true/false if the provided key is defined in the cache
*
* @param string $key the key to lookup in the local cache
*
* @return boolean
* @access public
*
*/
public function has($key)
{
return isset($this->cache_data[$key]);
}
/**
* returns the value for the given key
*
* @param string $key the key to lookup in the local cache
*
* @return mixed returns the cache data on sucess, false on error
* @access public
*
*/
public function get($key)
{
if (isset($this->cache_data[$key])) {
if ($this->cache_serializer == 'json') {
return json_decode($this->cache_data[$key]['object']);
} else {
return unserialize($this->cache_data[$key]['object']);
}
} else {
return false;
}
}
/**
* adds a new key/value pair to the cache
*
* @param string $key the key for the new cache entry
* @param mixed $data the data to store in cache
*
* @return void
* @access public
*
*/
public function put($key, $data)
{
$ttl = 86400 * 365;
//
// clear the rdata values
//
$data->rdata = '';
$data->rdlength = 0;
//
// find the lowest TTL, and use that as the TTL for the whole cached
// object. The downside to using one TTL for the whole object, is that
// we'll invalidate entries before they actuall expire, causing a
// real lookup to happen.
//
// The upside is that we don't need to require() each RR type in the
// cache, so we can look at their individual TTL's on each run- we only
// unserialize the actual RR object when it's get() from the cache.
//
foreach ($data->answer as $index => $rr) {
if ($rr->ttl < $ttl) {
$ttl = $rr->ttl;
}
$rr->rdata = '';
$rr->rdlength = 0;
}
foreach ($data->authority as $index => $rr) {
if ($rr->ttl < $ttl) {
$ttl = $rr->ttl;
}
$rr->rdata = '';
$rr->rdlength = 0;
}
foreach ($data->additional as $index => $rr) {
if ($rr->ttl < $ttl) {
$ttl = $rr->ttl;
}
$rr->rdata = '';
$rr->rdlength = 0;
}
$this->cache_data[$key] = array(
'cache_date' => time(),
'ttl' => $ttl
);
if ($this->cache_serializer == 'json') {
$this->cache_data[$key]['object'] = json_encode($data);
} else {
$this->cache_data[$key]['object'] = serialize($data);
}
}
/**
* runs a clean up process on the cache data
*
* @return void
* @access protected
*
*/
protected function clean()
{
if (count($this->cache_data) > 0) {
//
// go through each entry and adjust their TTL, and remove entries that
// have expired
//
$now = time();
foreach ($this->cache_data as $key => $data) {
$diff = $now - $data['cache_date'];
if ($data['ttl'] <= $diff) {
unset($this->cache_data[$key]);
} else {
$this->cache_data[$key]['ttl'] -= $diff;
$this->cache_data[$key]['cache_date'] = $now;
}
}
}
}
/**
* runs a clean up process on the cache data
*
* @return mixed
* @access protected
*
*/
protected function resize()
{
if (count($this->cache_data) > 0) {
//
// serialize the cache data
//
if ($this->cache_serializer == 'json') {
$cache = json_encode($this->cache_data);
} else {
$cache = serialize($this->cache_data);
}
//
// only do this part if the size allocated to the cache storage
// is smaller than the actual cache data
//
if (strlen($cache) > $this->cache_size) {
while (strlen($cache) > $this->cache_size) {
//
// go through the data, and remove the entries closed to
// their expiration date.
//
$smallest_ttl = time();
$smallest_key = null;
foreach ($this->cache_data as $key => $data) {
if ($data['ttl'] < $smallest_ttl) {
$smallest_ttl = $data['ttl'];
$smallest_key = $key;
}
}
//
// unset the key with the smallest TTL
//
unset($this->cache_data[$smallest_key]);
//
// re-serialize
//
if ($this->cache_serializer == 'json') {
$cache = json_encode($this->cache_data);
} else {
$cache = serialize($this->cache_data);
}
}
}
if ( ($cache == 'a:0:{}') || ($cache == '{}') ) {
return null;
} else {
return $cache;
}
}
return null;
}
};
/*
* Local variables:
* tab-width: 4
* c-basic-offset: 4
* c-hanging-comment-ender-p: nil
* End:
*/
?>
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