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 $result;
}
shmop_read
(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)
shmop_read — Leer datos desde un segmento de memoria compartida
Descripción
shmop_read() leerá una cadena desde un segmento de memoria compartida.
Parámetros
-
shmid -
El identificador del segmento de memoria compartida creado por shmop_open()
-
start -
Offset desde el que comenzar a leer
-
count -
El número de bytes a leer.
0leeshmop_size($shmid) - $startbytes.
Valores devueltos
Devuelve los datos o false en caso de error.
Ejemplos
Ejemplo #1 Lectura de un segmento de memoria compartida
<?php
$shm_data = shmop_read($shm_id, 0, 50);
?>
Este ejemplo, leerá los 50 primeros bytes del segmento de memoria compartida y almacenará los datos en
la variable $shm_data.
add a note
User Contributed Notes 5 notes
Craig Manley ¶
19 years ago
macmaster at pobox dot com ¶
23 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.
michael dot wuertz at six dot de ¶
3 years 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");
slavapl at mailandnews dot com ¶
23 years ago
Also you can use the shmop_size() function to determine the block size.
Milan Cvejic ¶
15 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));
?>
