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shmop_read

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

shmop_readLeer datos desde un segmento de memoria compartida

Descripción

shmop_read(resource $shmid, int $start, int $count): string

shmop_read() leerá una cadena desde un segmento de memoria compartida.

Parámetros

shmid

El identificador del segmento de memoria compartida creado por shmop_open()

start

Offset desde el que comenzar a leer

count

El número de bytes a leer. 0 lee shmop_size($shmid) - $start bytes.

Valores devueltos

Devuelve los datos o false en caso de error.

Historial de cambios

Versión Descripción
7.0.0 El tipo de shmid ha sido cambiado de int a resource.

Ejemplos

Ejemplo #1 Lectura de un segmento de memoria compartida

<?php
$shm_data 
shmop_read($shm_id050);
?>

Este ejemplo, leerá los 50 primeros bytes del segmento de memoria compartida y almacenará los datos en la variable $shm_data.

Ver también

  • shmop_write() - Escribir datos en un segmento de memoria compartida

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User Contributed Notes 5 notes

up
6
Craig Manley
16 years ago
shmop_read() reads and returns the whole memory segment's data. This is not useful if you're just working with strings. If you need to read a string from shared memory, call str_from_mem() on the result of shmop_read(). Similarly when writing strings to memory (instead of binary data), null terminate your strings with str_to_nts() before passing the value on to shmop_write().

function str_to_nts($value) {
  return "$value\0";
}

function str_from_mem(&$value) {
  $i = strpos($value, "\0");
  if ($i === false) {
    return $value;
  }
  $result =  substr($value, 0, $i);
  return $result;
}
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2
macmaster at pobox dot com
20 years ago
When i need to read the whole string at that shm pointer, setting the count parameter to zero (0) seems work for me.
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0
michael dot wuertz at six dot de
3 months ago
With shmop_read, you probably get a "\0" - padded string.

$zero_padded = shmop_read($shm_seg, 0, 128);

$usable_string = rtrim($zero_padded, "\0");
up
-1
slavapl at mailandnews dot com
20 years ago
Also you can use the shmop_size() function to determine the block size.
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-22
Milan Cvejic
12 years ago
You should always serialize data written in shared memory.
And when you are reading data you should always unserialize.

<?php

$data
= 'test';
$shm_bytes_written = shmop_write($shm_id, serialize($data), 0);
$shm_data = unserialize(shmop_read($shm_id, 0, $shm_bytes_written));
?>
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