PHP implementation read Memory sequence number _php tutorial

PHP implementation read Memory sequence number

This article mainly introduces the PHP implementation of reading memory sequence number, very simple and practical, the need for friends can refer to the next

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semWrapper.class.php

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/* * Semaphore (Semaphore). * This is a wrapper class that addresses different implementations of "semaphores" under different platforms. * This class is only symbolic at the moment, and it is actually an empty run under the Windows platform (and does not really implement mutexes). */ 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

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/* * Sequence number generator. */ Class Seqgenerator { Const SHM_KEY = 1; /** * Initialization of Sequence number generator. * Only the first call after server startup is valid, and calling this method after this does not actually work. * @param int $start The starting value of the sequence number. * @return Boolean returns true to indicate success. */ static public function init ($start = 1) { Mutual exclusion through semaphores to avoid access violation of shared memory $SW = new Semwrapper; if (! $SW->acquire ()) { return false; } Open Shared Memory $shm _id = Shmop_open (Self::shm_key, ' n ', 0644, 4); if (Empty ($shm _id)) { Because the ' n ' mode is used, if shared memory cannot be opened, you can assume that the shared memory has been created without having to initialize it again $SW->release (); return true; } Write an initial value in shared memory $size = Shmop_write ($shm _id, pack (' L ', $start), 0); if ($size! = 4) { Shmop_close ($shm _id); $SW->release (); return false; } Turn off shared memory, release semaphores Shmop_close ($shm _id); $SW->release (); return true; } /** * Generate the next order number. * Order number generated by @return int */ static public Function Next () { Mutual exclusion through semaphores to avoid access violation of shared memory $SW = new Semwrapper; if (! $SW->acquire ()) { return 0; } Open Shared Memory $shm _id = Shmop_open (Self::shm_key, ' W ', 0, 0); if (Empty ($shm _id)) { $SW->release (); return 0; } To read a sequential number from shared memory $data = Shmop_read ($shm _id, 0, 4); if (empty ($data)) { $SW->release (); return 0; } $arr = Unpack (' L ', $data); $seq = $arr [1]; Write the next sequential number to shared memory $size = Shmop_write ($shm _id, pack (' L ', $seq + 1), 0); if ($size! = 4) { $SW->release (); return 0; } Turn off shared memory, release semaphores Shmop_close ($shm _id); $SW->release (); return $seq; } }

page.php

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How to use $seq = Seqgenerator::next (); Var_dump ($SEQ);

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