Shared memory file in PHP - php

Question

I use openssl_pkcs7_sign and openssl_pkcs7_encrypt to create encrypted data. The functions only accept file names. I would like to store the temporary files in shared memory to improve performance. I understand in Linux I can file_put_contents('/dev/shm/xxx', data), but it is not possible for Windows. Is there portable way in PHP to do this? Would shmop_ function help here? Thanks.
PS: Or is there way to make these functions accept data strings?
PS2: Please do not suggest invoking /usr/bin/openssl from PHP. It is not portable.

Answer 1

Ok, so the way I would suggest doing this is with a file stream wrapper. Let me whip up a quick example:
class staticStreamWrapper {
public $context;
protected static $data = array();
protected $path = '';
protected $pointer = 0;
protected $writable = false;
public function stream_close() {}
public function stream_eof() {
return $this->pointer >= strlen(static::$data[$this->path]);
}
public function stream_flush() {}
public function stream_open($path, $mode, $options, &$opened_path) {
switch ($mode[0]) {
case 'r':
if (!isset(static::$data[$path])) return false;
$this->path = $path;
$this->writable = isset($mode[1]) && $mode[1] == '+';
break;
case 'w':
static::$data[$path] = '';
$this->path = $path;
$this->writable = true;
break;
case 'a':
if (!isset(static::$data[$path])) static::$data[$path] = '';
$this->path = $path;
$this->writable = true;
$this->pointer = strlen(static::$data[$path]);
break;
case 'x':
if (isset(static::$data[$path])) return false;
$this->path = $path;
$this->writable = true;
break;
case 'c':
if (!isset(static::$data[$path])) static::$data[$path] = '';
$this->path = $path;
$this->writable = true;
break;
default:
return false;
}
$opened_path = $this->path;
return true;
}
public function stream_read($count) {
$bytes = min(strlen(static::$data[$this->path]) - $this->pointer, $count);
$data = substr(static::$data[$this->path], $this->pointer, $bytes);
$this->pointer += $bytes;
return $data;
}
public function stream_seek($offset, $whence = SEEK_SET) {
$len = strlen(static::$data[$this->path]);
switch ($whence) {
case SEEK_SET:
if ($offset <= $len) {
$this->pointer = $offset;
return true;
}
break;
case SEEK_CUR:
if ($this->pointer + $offset <= $len) {
$this->pointer += $offset;
return true;
}
break;
case SEEK_END:
if ($len + $offset <= $len) {
$this->pointer = $len + $offset;
return true;
}
break;
}
return false;
}
public function stream_stat() {
$size = strlen(static::$data[$this->path]);
$time = time();
return array(
0 => 0,
'dev' => 0,
1 => 0,
'ino' => 0,
2 => 0777,
'mode' => 0777,
3 => 1,
'nlink' => 1,
4 => 0,
'uid' => 0,
5 => 0,
'gid' => 0,
6 => '',
'rdev' => '',
7 => $size,
'size' => $size,
8 => $time,
'atime' => $time,
9 => $time,
'mtime' => $time,
10 => $time,
'ctime' => $time,
11 => -1,
'blksize' => -1,
12 => -1,
'blocks' => -1,
);
}
public function stream_tell() {
return $this->pointer;
}
public function stream_write($data) {
if (!$this->writable) return 0;
$size = strlen($data);
$len = strlen(static::$data[$this->path]);
if ($this->stream_eof()) {
static::$data[$this->path] .= $data;
} else {
static::$data[$this->path] = substr_replace(
static::$data[$this->path],
$data,
$this->pointer
);
}
$this->pointer += $size;
return $size;
}
public function unlink($path) {
if (isset(static::$data[$path])) {
unset(static::$data[$path]);
}
return true;
}
}
Now, you would then need to register the wrapper:
stream_wrapper_register('static', 'staticStreamWrapper');
So you now can treat it like a file even though it never actually leaves PHP (it's stored as a static variable)!
file_put_contents('static://foo.txt', 'this is my data');
file_get_contents('static://foo.txt'); // "this is my data"
$f = fopen('static://foo.txt', 'r'); // should return a resource
// etc...

Answer 2

Since Windows 2000, the shmop (previously shm_) methods are available.
shmop_open uses a unique integer key to share the memory area. ftok can be used to produce a unique index based on a file path (typically your script file's full path). Any instance that shares the same key can share the same memory.
http://php.net/manual/en/ref.shmop.php
Tested on PHP Version 5.3.3 from Zend Server CE
System Windows NT CRYPE 6.1 build 7601 (Unknow Windows version Business Edition Service Pack 1) i586
<?php
$key = ftok(__FILE__, 't');
$memory = shmop_open($key, "c", 0600, 16 * 1024);
$data = array('data' => 'value');
$bytes = shmop_write($memory, serialize($data), 0);
$return = shmop_read($memory, 0, $bytes);
print_r(unserialize($return));
?>
shmop_read/shmop_write stores raw bytes from a string, so you don't need to serialize it, but you will need to write the length of the string somewhere. My example creates a 16KB shared memory area, you can of course size it to fit the openssl file plus the space you need to store the file size.