PHP memcache ring queue

PHP memcache ring queue class. I'm a newbie and haven't learned much about data structures. Because of business needs, I just simulated it! The prototype is the PHP memcache queue code shared by lusi on oschina. In order to ensure that the queue can be entered and exited at any time without the danger of the int length crossing the boundary (if the single chain adopts Head auto-increment, there is a possibility of crossing the boundary without processing), so it is simply rewritten into a circular queue.There may be bugs, sorry!

/**
 * PHP memcache ring queue class
 * Original author LKK/lianq.net
 * Modified FoxHunter
 * Due to business needs, only the Pop and Push in the queue are retained. Modify the expiration time to 0, which is permanent
*/
class MQueue
{
 public static $client;

 private $expire; //Expiration time, seconds, 1~2592000, that is, within 30 days
 private $sleepTime; //Waiting time to unlock, microseconds
 private $queueName; //Queue name, unique value
 private $retryNum; //Number of attempts
 private $MAXNUM; //Maximum queue capacity
 private $canRewrite; // Is it possible to overwrite the switch, and the full content will overwrite the original data from the head

 private $HEAD; //The pointer position to be entered in the next step
 private $TAIL; //The pointer position to be entered in the next step
 private $LEN; //The current length of the queue

 const LOCK_KEY = '_Fox_MQ_LOCK_'; //Lock storage indicator
 const LENGTH_KEY = '_Fox_MQ_LENGTH_'; //The current length storage indicator of the queue
 const VALU_KEY = '_Fox_MQ_VAL_'; //Queue Key-value storage indicator
 const HEAD_KEY = '_Fox_MQ_HEAD_'; // Queue HEAD pointer location indicator
 const TAIL_KEY = '_Fox_MQ_TAIL_'; // Queue TAIL pointer location indicator

 /*
 * Constructor
 * For the same $queueName, When instantiating, you must ensure that the parameter values ​​of the constructor are consistent, otherwise pop and push will cause confusion in the queue order
 */
 public function __construct($queueName = '', $maxqueue = 1, $canRewrite = false, $expire = 0, $config = '')
 {
 if (empty($config)) {
 self::$client = memcache_pconnect('127.0.0.1', 11211);
 } elseif (is_array($config)) { //array ('host'=>'127.0.0.1','port'=>'11211')
 self::$client = memcache_pconnect($config['host'], $config['port']);
 } elseif (is_string($config)) { //"127.0.0.1:11211"
 $tmp = explode(':', $config);
 $conf['host'] = isset($tmp[0]) ? $tmp[0] : '127.0.0.1';
 $conf['port'] = isset($tmp[1]) ? $tmp[1] : '11211';
 self::$client = memcache_pconnect( $conf['host'], $conf['port']);
 }
 if (!self::$client)
 return false;
 ignore_user_abort(true); //When the client disconnects, allow execution to continue
 set_time_limit(0); //Cancel the upper limit of script execution delay
 $this->access = false;
 $this->sleepTime = 1000;
 $expire = (empty($expire)) ? 0 : (int ) $expire + 1;
 $this->expire = $expire;
 $this->queueName = $queueName;
 $this->retryNum = 20000;
 $this->MAXNUM = $maxqueue != null ? $maxqueue : 1;
 $this->canRewrite = $canRewrite;
 $this->getHeadAndTail();
 if (!isset($this->HEAD) || empty($this-> HEAD))
 $this->HEAD = 0;
 if (!isset($this->TAIL) || empty($this->TAIL))
 $this->TAIL = 0;
 if (!isset($this->LEN) || empty($this->LEN))
 $this->LEN = 0;

 }

 //Get the head and tail pointer information and length of the queue
 private function getHeadAndTail()
 {
 $this->HEAD = (int) memcache_get(self::$client, $this->queueName . self::HEAD_KEY);
 $this->TAIL = (int) memcache_get( self::$client, $this->queueName . self::TAIL_KEY);
 $this->LEN = (int) memcache_get(self::$client, $this->queueName . self::LENGTH_KEY) ;
 }


 // Use memcache_add atomic lock
 private function lock()
 {
 if ($this->access === false) {
 $i = 0;
 while (!memcache_add(self ::$client, $this->queueName . self::LOCK_KEY, 1, false, $this->expire)) {
 usleep($this->sleepTime);
 @$i++;
 if ($ i > $this->retryNum) { //Try to wait N times
 return false;
 break;
 }
 }
 return $this->access = true;
 }
 return false;
 }

 / /Update the head pointer to point to the next position
 private function incrHead()
 {
 //$this->getHeadAndTail(); //Get the latest pointer information, since this method body is called within the lock, its lock This method has been called, this line comment
 $this->HEAD++; //Move the head pointer down
 if ($this->HEAD >= $this->MAXNUM) {
 $this-> ;HEAD = 0; //Boundary value correction
 }
 ;
 $this->LEN--; //The movement of Head is triggered by Pop, so it is equivalent to a reduction in quantity
 if ($this->LEN < 0) {
 $this->LEN = 0; //Boundary value correction
 }
 ;
 memcache_set(self::$client, $this->queueName . self::HEAD_KEY, $this->HEAD, false, $this->expire); //Update
 memcache_set(self::$client, $this->queueName . self::LENGTH_KEY, $this->LEN, false, $this->expire); //Update

 }

 //Update the tail The pointer points to the next position
 private function incrTail()
 {

 //$this->getHeadAndTail(); //Get the latest pointer information, since this method body is called within the lock, it has been called within the lock For this method, comment this line
 $this->TAIL++; //Move the tail pointer down
 if ($this->TAIL >= $this->MAXNUM) {
 $this->TAIL = 0 ; //Boundary value correction
 }
 ;
 $this->LEN++; //Head’s movement is triggered by Push, so it is equivalent to an increase in quantity
 if ($this->LEN >= $this->MAXNUM ) {
 $this->LEN = $this->MAXNUM; //Boundary value length correction
 }
 ;
 memcache_set(self::$client, $this->queueName . self::TAIL_KEY, $this ->TAIL, false, $this->expire); //Update
 memcache_set(self::$client, $this->queueName . self::LENGTH_KEY, $this->LEN, false, $this ->expire); //Update
 }


 //Unlock
 private function unLock()
 {
 memcache_delete(self::$client, $this->queueName . self::LOCK_KEY);
 $this ->access = false;
 }

 //Determine whether the queue is full
 public function isFull()
 {
 //When called directly from the outside, there is no lock, so the value here is an approximate value and not very accurate. But the internal call is credible because there is a lock in front of it
 if ($this->canRewrite)
 return false;
 return $this->LEN == $this->MAXNUM ? true : false;
 }

 //Judge whether it is empty
 public function isEmpty()
 {
 //When called directly from the outside, since there is no lock, the value here is an approximate value and not very accurate. However, because there is a lock in front of the internal call, so Trusted
 return $this->LEN == 0 ? true : false;
 }

 public function getLen()
 {
 //When called directly from the outside, there is no lock, so the value here is an approximate value, and Not very accurate, but the internal call has a lock in front, so it is credible
 return $this->LEN;
 }

 /*
 * push value
 * @param mixed value
 * @return bool
 */
 public function push($data = '')
 {

 $result = false;
 if (empty($data))
 return $result;

 if (!$this->lock()) {
 return $result;
 }

 $this->getHeadAndTail(); //Get the latest pointer information

 if ($this->isFull()) { //The Full concept is only available under non-overwriting
 $ this->unLock();
 return false;
 }

 if (memcache_set(self::$client, $this->queueName . self::VALU_KEY . $this->TAIL, $data, MEMCACHE_COMPRESSED, $this->expire)) {
 //After pushing, it is found that the tail and the head overlap (the pointer has not moved yet), and there is still data on the right that has not been read by the Head, then move the Head pointer to avoid the tail Pointer spans Head
 if ($this->TAIL == $this->HEAD && $this->LEN >= 1) {
 $this->incrHead();
 }
 $this-> ;incrTail(); //Move the tail pointer
 $result = true;
 }

 $this->unLock();
 return $result;
 }


 /*
 * Pop a value
 * @param [length] int queue length
 * @return array
 */
 public function pop($length = 0)
 {
 if (!is_numeric($length))
 return false;

 if (!$this-> lock())
 return false;

 $this->getHeadAndTail();

 if (empty($length))
 $length = $this->LEN; //Read all by default

 if ( $this->isEmpty()) {
 $this->unLock();
 return false;
 }
 //Correction after the length exceeds the queue length
 if ($length > $this->LEN )
 $length = $this->LEN;

 $data = $this->popKeyArray($length);
 $this->unLock();
 return $data;
 }


 /*
 * pop the value of a certain length
 * @param [length] int queue length
 * @return array
 */
 private function popKeyArray($length)
 {

 $result = array();
 if (empty($length))
 return $result;
 for ($k = 0; $k < $length; $k++) {
 $result[] = @memcache_get(self::$client, $this ->queueName . self::VALU_KEY . $this->HEAD);
 @memcache_delete(self::$client, $this->queueName . self::VALU_KEY . $this->HEAD, 0);
 //After extracting the value, it is found that the head and tail overlap (the pointer has not moved at this time), and there is no data on the right, that is, the last data in the queue is completely emptied. At this time, the pointer stays local and does not move. The queue length becomes 0
 if ($this->TAIL == $this->HEAD && $this->LEN <= 1) {
 $this->LEN = 0;
 memcache_set(self::$ client, $this->queueName . self::LENGTH_KEY, $this->LEN, false, $this->expire); //Update
 break;
 } else {
 $this->incrHead() ; //The head and tail do not overlap, or they overlap but there is still unread data, move the HEAD pointer to the next position to be read
 }
 }
 return $result;
 }

 /*
 * Reset Queue
 * * @return NULL
 */
 private function reset($all = false)
 {

 if ($all) {
 memcache_delete(self::$client, $this->queueName . self::HEAD_KEY , 0);
 memcache_delete(self::$client, $this->queueName . self::TAIL_KEY, 0);
 memcache_delete(self::$client, $this->queueName . self::LENGTH_KEY, 0 );
 } else {
 $this->HEAD = $this->TAIL = $this->LEN = 0;
 memcache_set(self::$client, $this->queueName . self::HEAD_KEY , 0, false, $this->expire);
 memcache_set(self::$client, $this->queueName . self::TAIL_KEY, 0, false, $this->expire);
 memcache_set(self ::$client, $this->queueName . self::LENGTH_KEY, 0, false, $this->expire);
 }
 }

 /*
 * Clear all memcache cache data
 * @return NULL
 */
 public function memFlush()
 {
 memcache_flush(self::$client);
 }


 public function clear($all = false)
 {
 if (!$this->lock())
 return false;
 $this->getHeadAndTail();
 $Head = $this->HEAD;
 $Length = $this->LEN;
 $curr = 0;
 for ($i = 0; $ i < $Length; $i++) {
 $curr = $this->$Head + $i;
 if ($curr >= $this->MAXNUM) {
 $this->HEAD = $ curr = 0;
 }
 @memcache_delete(self::$client, $this->queueName . self::VALU_KEY . $curr, 0);
 }


 $this->unLock();
 $ this->reset($all);
 return true;
 }


}