C. Funkce pro pr�ci se sd�lenou pam�t�

�vod

Shmop je snadno pou�iteln� sada funkc�, kter� PHP umo��uje ��st, zapisovat, vytv��et a mazat segmenty UNIXov� sd�len� pam�ti. Tyto funkce na Windows p�edch�zej�c�ch Windows 2000 nefunguj�.

Pozn�mka: N�zvy funkc� popisovan�ch v t�to kapitole za��naj� v PHP 4.0.3 na shm_(), ale od PHP 4.0.4 se jejich n�zvy zm�nily na shmop_().

Po�adavky

Tyto funkce jsou k dispozici jako sou��st standardn�ho modulu, kter� je v�dy dostupn�.

Instalace

Pokud chcete shmop pou��vat, mus�te PHP zkompilovat s volbou --enable-shmop.

Konfigurace b�hu

Toto roz��en� nem� definov�no ��dn� konfigura�n� direktivy.

Typy prost�edk�

P�eddefinovan� konstanty

Toto roz��en� nem� definov�ny ��dn� konstanty.

P��klady

P��klad 1. Shared Memory Operations Overview

<?php // Vytvo�it 100 bytov� blok sd�len� pam�ti se system id 0xff3 $shm_id = shmop_open(0xff3, "c", 0644, 100); if (!$shm_id) { echo "Nepoda�ilo se vytvo�it segment sd�len� pam�ti\n"; } // Zjistit velikost bloku sd�len� pam�ti $shm_size = shmop_size($shm_id); echo "SHM blok o velikosti : ".$shm_size. " byl vytvo�en.\n"; // Zap�eme do sd�len� pam�ti zku�ebn� �et�zec $shm_bytes_written = shmop_write($shm_id, "my shared memory block", 0); if ($shm_bytes_written != strlen("my shared memory block")) { echo "Nepoda�ilo se zapsat kompletn� data\n"; } // Na�teme �et�zec zp�tky $my_string = shmop_read($shm_id, 0, $shm_size); if (!$my_string) { echo "Nepoda�ilo se ��st z bloku sd�len� pam�ti\n"; } echo "Data ve sd�len� pam�ti byla: ".$my_string."\n"; // Sma�eme tento blok a zav�eme segment sd�len� pam�ti if (!shmop_delete($shm_id)) { echo "Nepoda�ilo se smazat blok sd�len� pam�ti."; } shmop_close($shm_id); ?>

Obsah
shmop_close -- Zav��t blok sd�len� pam�ti
shmop_delete -- Smazat blok sd�len� pam�ti
shmop_open -- Vytvo�it nebo otev��t blok sd�len� pam�ti
shmop_read -- P�e��st data z bloku sd�len� pam�ti
shmop_size -- Zjistit velikost bloku sd�len� pam�ti
shmop_write -- Zapsat data do bloku sd�len� pam�ti

add a note User Contributed Notes
Funkce pro pr�ci se sd�lenou pam�t�

joeldg AT listbid.com
02-May-2003 07:48


Just so you know, the ftok function is probably the best for getting the key.. just so there are not people confused with how they are coming up with these hex codes for the id.



$fsize = filesize("/home/joeldg/testdata");

$fdata = file_get_contents("/home/joeldg/testdata");

$shm_id = shmop_open(ftok("/home/joeldg/testdata", 'R'), "c", 0644, $fsize);

stoimenov at email dot com
24-Jul-2002 12:18


Windows does support shared memory through memory mapped file. Check the following functions for details:



 * CreateFileMapping

 * MapViewOfFile

hackie at misato dot prohost dot org
02-May-2002 01:15


Your segment probobly doesn't exist. You should probobly be using the c flag... 



      "a" for access (sets SHM_RDONLY for shmat) use this flag when you need to open an existing shared memory segment for read only



      "c" for create (sets IPC_CREATE) use this flag when you need to create a new shared memory segment or if a segment with the same key exists, try to open it for read and write

medvitz at medvitz dot net
30-Mar-2002 05:53


These functions work on windows.  You have to install as an ISAPI filter, but these functions work great......

rei at prohost dot org
11-Jan-2001 11:16


The idea behind SHMOP is an easy to use shared memory interface, 


without any additional headers added to the shared memory segment 


or requiring any special special controls to access the shared memory


segment outside of PHP. SHMOP borrows its api from C's api to shm,


which makes it very easy to use, because it treats shared memory, like C, as    


a file of sorts. This makes it very easy to use even for novices, due to this  


functionality. Most importantly SHMOP uses shm segments to store raw data,


which means you don't need to worry about matching headers, etc... when you are


using C, perl or other programming languages to open/create/read/write shm segments


that were create or are going to be used by PHP. In this it differs from


sysvshm, who's shm interface uses a specialized header, which resides inside


the shared memory segment this adds an unnecessary level of difficulty when


you want to access php shm from external programs.


Also, from my personal tests in Linux 2.2/2.4 and FreeBSD 3.3 SHMOP is about


20% faster then sysvshm, mostly due to fact it does not need to parse the


specialized header and stores the data in raw form.

slavapl at mailandnews dot com
11-Jan-2001 11:02


What you need to realise is that sysvshm is extremly php oriented in it's ability, it's quite a kludge interfacing other NON PHP utilities with it. For example have you tried using sysvshm to read an shm segment NOT created by php? It's not possible, because sysvshm uses a proprietry format, in essense it can ONLY be used within PHP unless of course you take time to figure out this format. 


So basically, the purpose of shmop is to provide a symple interface to shared memory that can be used with OTHER NON php shm creators. 





Hope this clears it up.

add a note


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