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 $result;
}
shmop_read
(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)
shmop_read — Read data from shared memory block
Descrição
shmop_read() will read a string from shared memory block.
Parâmetros
-
shmop -
The shared memory block identifier created by shmop_open()
-
offset -
Offset from which to start reading; must be greater than or equal to zero and less than or equal to the actual size of the shared memory segment.
-
size -
The number of bytes to read; must be greater than or equal to zero, and the sum of
offsetandsizemust be less than or equal to the actual size of the shared memory segment.0readsshmop_size($shmid) - $startbytes.
Valor Retornado
Returns the data ou false em caso de falha.
Erros/Exceções
If offset or size are out of range,
a ValueError is thrown.
Registro de Alterações
| Versão | Descrição |
|---|---|
| 8.0.0 |
shmop expects a Shmop
instance now; previously, a resource was expected.
|
| 8.0.0 |
If offset or size are out of range,
a ValueError is thrown; previously E_WARNING
was emitted, and false was returned,
|
Exemplos
Exemplo #1 Reading shared memory block
<?php
$shm_data = shmop_read($shm_id, 0, 50);
?>
This example will read 50 bytes from shared memory block and place the data
inside $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));
?>
