Php implementation of reading memory sequence number _ PHP Tutorial

Php implements sequential number of read memory. Php to read the memory sequence number this article mainly introduces php to read the memory sequence number, which is very simple and practical. if you need a friend, you can refer to it for record, osc this site should have a php-intensive implementation of reading the memory sequence number

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SemWrapper. class. php

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/* * 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

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/* * 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 through semaphores to avoid access conflicts to the shared memory $ Sw = new SemWrapper; If (! $ Sw-> acquire ()){ Return false; } // Enable shared memory $ Shm_id = shmop_open (self: SHM_KEY, 'n', 0644, 4 ); If (empty ($ shm_id )){ // Because the 'n' mode is used, if you cannot enable the shared memory, you can think that the shared memory has been created and you do not need to initialize it again. $ Sw-> release (); Return true; } // Write the initial value to the shared memory $ Size = shmop_write ($ shm_id, pack ('L', $ start), 0 ); If ($ size! = 4 ){ Shmop_close ($ shm_id ); $ Sw-> release (); Return false; } // Disable shared memory and release semaphores Shmop_close ($ shm_id ); $ Sw-> release (); Return true; } /** * Generate the next sequence number. * @ Return int indicates the sequence number generated. */ Static public function next () { // Mutex through semaphores to avoid access conflicts to the shared memory $ Sw = new SemWrapper; If (! $ Sw-> acquire ()){ Return 0; } // Enable shared memory $ Shm_id = shmop_open (self: SHM_KEY, 'W', 0, 0 ); If (empty ($ shm_id )){ $ Sw-> release (); Return 0; } // Read the sequence number from the 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 sequence number to the shared memory $ Size = shmop_write ($ shm_id, pack ('L', $ seq + 1), 0 ); If ($ size! = 4 ){ $ Sw-> release (); Return 0; } // Disable shared memory and release semaphores Shmop_close ($ shm_id ); $ Sw-> release (); Return $ seq; } }

Page. php

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// Usage $ Seq = SeqGenerator: next (); Var_dump ($ seq );

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This article describes how to read the serial number of the memory in php. it is very simple and practical. if you need it, you can refer to it as a record. the osc site should be heavy...