Php implements READ memory sequence number _ php instance

This article mainly introduces php's implementation of reading the memory sequence number, which is very simple and practical. If you need it, you can refer to it as a record. The osc site should have repeated

SemWrapper. class. php

/** Semaphore ). * This is a packaging class used to solve different implementation methods of the "semaphore" on different platforms. * Currently, this class is symbolic. It is actually a dry run on Windows platforms (and does not actually implement mutual exclusion ). */Class SemWrapper {private $ hasSemSupport; private $ sem; const SEM_KEY = 1; public function _ construct () {$ this-> hasSemSupport = function_exists ('sem _ get'); if ($ this-> hasSemSupport) {$ this-> sem = sem_get (self :: SEM_KEY) ;}} public function acquire () {if ($ this-> hasSemSupport) {return sem_acquire ($ this-> sem);} return true;} public function release () {if ($ this-> hasSemSupport) {return sem_release ($ this-> sem);} return true ;}}

SeqGenerator. class. php

/** Sequence number generator. */Class SeqGenerator {const SHM_KEY = 1;/*** initialize the sequence number generator. * This method is valid only when it is called for the first time after the server is started. * @ Param int $ start generates the starting value of the sequence number. * @ Return boolean true indicates success. */Static public function init ($ start = 1) {// mutex is implemented through semaphores to avoid access conflicts to shared memory $ sw = new SemWrapper; if (! $ Sw-> acquire () {return false;} // open the shared memory $ shm_id = shmop_open (self: SHM_KEY, 'n', 0644, 4 ); if (empty ($ shm_id) {// because the 'N' mode is used, if the shared memory cannot be enabled, you can think that the shared memory has been created, no need to initialize $ sw-> release (); return true;} // write the initial value $ size = shmop_write ($ shm_id, pack ('l ', $ start), 0); if ($ size! = 4) {shmop_close ($ shm_id); $ sw-> release (); return false;} // close the shared memory and release the semaphores shmop_close ($ shm_id ); $ sw-> release (); return true;}/*** generates the next sequence number. * @ Return int the sequence number */static public function next () {// mutex through semaphores to avoid access conflicts to shared memory $ sw = new SemWrapper; if (! $ Sw-> acquire () {return 0;} // open the shared memory $ shm_id = shmop_open (self: SHM_KEY, 'w', 0, 0 ); if (empty ($ shm_id) {$ sw-> release (); return 0;} // read the sequence number $ data = shmop_read ($ shm_id, 0, 4); if (empty ($ data) {$ sw-> release (); return 0 ;}$ arr = unpack ('l', $ data ); $ seq = $ arr [1]; // write the next sequence number to the shared memory $ size = shmop_write ($ shm_id, pack ('l', $ seq + 1), 0 ); if ($ size! = 4) {$ sw-> release (); return 0 ;}// close the shared memory and release the semaphores shmop_close ($ shm_id); $ sw-> release (); return $ seq ;}}

Page. php

// Usage method $ seq = SeqGenerator: next (); var_dump ($ seq );

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