Memcached::cas

(PECL memcached >= 0.1.0)

Memcached::cas — Compare and swap an item

Açıklama

public bool Memcached::cas ( float $cas_token , string $key , mixed $value [, int $expiration ] )

Memcached::cas() performs a "check and set" operation, so that the item will be stored only if no other client has updated it since it was last fetched by this client. The check is done via the cas_token parameter which is a unique 64-bit value assigned to the existing item by memcache. See the documentation for Memcached::get*() methods for how to obtain this token. Note that the token is represented as a double due to the limitations of PHP's integer space.

Değiştirgeler

cas_token: Unique value associated with the existing item. Generated by memcache.
key: Değerin saklanacağı anahtar.
value: Saklanacak değer.
expiration: Zaman aşımı, öntanımlı 0'dır. Daha ayrıntılı bilgi için Zaman aşımı süreleri bölümüne bakınız.

Dönen Değerler

Başarı durumunda TRUE, başarısızlık durumunda FALSE döner. The Memcached::getResultCode() will return Memcached::RES_DATA_EXISTS if the item you are trying to store has been modified since you last fetched it.

Örnekler

Örnek 1 Memcached::cas() example


<?php
$m = new Memcached();
$m->addServer('localhost', 11211);

do {
    /* fetch IP list and its token */
    $ips = $m->get('ip_block', null, $cas);
    /* if list doesn't exist yet, create it and do
       an atomic add which will fail if someone else already added it */
    if ($m->getResultCode() == Memcached::RES_NOTFOUND) {
        $ips = array($_SERVER['REMOTE_ADDR']);
        $m->add('ip_block', $ips);
    /* otherwise, add IP to the list and store via compare-and-swap
       with the token, which will fail if someone else updated the list */
    } else { 
        $ips[] = $_SERVER['REMOTE_ADDR'];
        $m->cas($cas, 'ip_block', $ips);
    }   
} while ($m->getResultCode() != Memcached::RES_SUCCESS);

?>

Ayrıca Bakınız

Memcached::casByKey() - Compare and swap an item on a specific server

add a note User Contributed Notes Memcached::cas

abodera at gmail dot com 27-Apr-2010 07:19


Watch out!





When using binary protocol, the expected result after cas() is 21 (Memcached::RES_END).





For example, to make the above example #1 work with binary protocol, use the following:


<?php


$m = new Memcached();


$m->addServer('localhost', 11211);


$m->setOption(Memcached::OPT_BINARY_PROTOCOL,true)





// [...]





    } else { 


        $ips[] = $_SERVER['REMOTE_ADDR'];


        $m->cas($cas, 'ip_block', $ips);


    }   


} while ($m->getResultCode() != Memcached::RES_END);


?>

add a note