/**
* Read from cache.
* @param string key
* @return mixed|NULL
*/
public function read($key)
{
$key = $this->prefix . $key;
$meta = $this->memcache->get($key);
if (!$meta) {
return NULL;
}
// meta structure:
// array(
// data => stored data
// delta => relative (sliding) expiration
// callbacks => array of callbacks (function, args)
// )
// verify dependencies
if (!empty($meta[self::META_CALLBACKS]) && !Cache::checkCallbacks($meta[self::META_CALLBACKS])) {
$this->memcache->delete($key);
return NULL;
}
if (!empty($meta[self::META_DELTA])) {
$this->memcache->replace($key, $meta, 0, $meta[self::META_DELTA] + time());
}
return $meta[self::META_DATA];
}
/**
* Verifies dependencies.
* @param array
* @return bool
*/
private function verify($meta)
{
do {
if (!empty($meta[self::META_DELTA])) {
// meta[file] was added by readMeta()
if (filemtime($meta[self::FILE]) + $meta[self::META_DELTA] < time()) {
break;
}
touch($meta[self::FILE]);
} elseif (!empty($meta[self::META_EXPIRE]) && $meta[self::META_EXPIRE] < time()) {
break;
}
if (!empty($meta[self::META_CALLBACKS]) && !Cache::checkCallbacks($meta[self::META_CALLBACKS])) {
break;
}
if (!empty($meta[self::META_ITEMS])) {
foreach ($meta[self::META_ITEMS] as $depFile => $time) {
$m = $this->readMeta($depFile, LOCK_SH);
if ($m[self::META_TIME] !== $time) {
break 2;
}
if ($m && !$this->verify($m)) {
break 2;
}
}
}
return TRUE;
} while (FALSE);
$this->delete($meta[self::FILE], $meta[self::HANDLE]);
// meta[handle] & meta[file] was added by readMeta()
return FALSE;
}
