PHP: Akım Sarmalayıcı olarak örnek bir sınıf tanımı

Akım Sarmalayıcı olarak örnek bir sınıf tanımı

Aşağıdaki örnekte, fread() gibi standart dosya sistemi akım işlevlerini kullanarak bir küresel değişkene okuma/yazma erişimini mümkün kılan bir var:// sarmalayıcısı gerçeklenmiştir. $GLOBALS["foo"] değişkenine veri yazma ve okuma işlemleri için "var://foo" URL'si kullanılacaktır.

Örnek 1 - Küresel değişkenlere veri okuyup yazan bir akım

<?php

class VariableStream {
  var $position;
  var $varname;

  function stream_open($path, $mode, $options, &$opened_path)
  {
    $url = parse_url($path);
    $this->varname = $url["host"];
    $this->position = 0;

    return true;
  }

  function stream_read($count)
  {
    $ret = substr($GLOBALS[$this->varname], $this->position, $count);
    $this->position += strlen($ret);
    return $ret;
  }

  function stream_write($data)
  {
    $left = substr($GLOBALS[$this->varname], 0, $this->position);
    $right = substr($GLOBALS[$this->varname], $this->position + strlen($data));
    $GLOBALS[$this->varname] = $left . $data . $right;
    $this->position += strlen($data);
    return strlen($data);
  }

  function stream_tell()
  {
    return $this->position;
  }

  function stream_eof()
  {
    return $this->position >= strlen($GLOBALS[$this->varname]);
  }

  function stream_seek($offset, $whence)
  {
    switch ($whence) {
      case SEEK_SET:
        if ($offset < strlen($GLOBALS[$this->varname]) && $offset >= 0) {
          $this->position = $offset;
          return true;
        } else {
          return false;
        }
        break;

      case SEEK_CUR:
        if ($offset >= 0) {
          $this->position += $offset;
          return true;
        } else {
          return false;
        }
        break;

      case SEEK_END:
        if (strlen($GLOBALS[$this->varname]) + $offset >= 0) {
          $this->position = strlen($GLOBALS[$this->varname]) + $offset;
          return true;
        } else {
          return false;
        }
        break;

      default:
        return false;
    }
  }
}

function stream_metadata($path, $option, $var)
{
    if($option == STREAM_META_TOUCH) {
        $url = parse_url($path);
        $varname = $url["host"];
        if(!isset($GLOBALS[$varname])) {
            $GLOBALS[$varname] = '';
        }
        return true;
    }
    return false;
}

stream_wrapper_register("var", "VariableStream")
    or die("Failed to register protocol");

$myvar = "";

$fp = fopen("var://myvar", "r+");

fwrite($fp, "line1\n");
fwrite($fp, "line2\n");
fwrite($fp, "line3\n");

rewind($fp);
while (!feof($fp)) {
    echo fgets($fp);
}
fclose($fp);
var_dump($myvar);

?>

Yukarıdaki örneğin çıktısı:

line1
line2
line3
string(18) "line1
line2
line3
"

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User Contributed Notes 1 note

down

pfe dot skh at gmail dot com ¶

14 years ago

Example of stream used with databases :

Requirement :
A MySQL database with a table named data structured as follow :
CREATE TABLE IF NOT EXISTS `data` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `data` varchar(255) NOT NULL,
  `when_inserted` datetime NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

Now with the stream implementation :

<?php

class DBStream {
    private $_pdo;
    private $_ps;
    private $_rowId = 0;

    function stream_open($path, $mode, $options, &$opath)
    {
        $url = parse_url($path);
        $url['path'] = substr($url['path'], 1);
        try{
            $this->_pdo = new PDO("mysql:host={$url['host']};dbname={$url['path']}", $url['user'], isset($url['pass'])? $url['pass'] : '', array());
        } catch(PDOException $e){ return false; }
        switch ($mode){
            case 'w' : 
                $this->_ps = $this->_pdo->prepare('INSERT INTO data VALUES(null, ?, NOW())');
                break;
            case 'r' : 
                $this->_ps = $this->_pdo->prepare('SELECT id, data FROM data WHERE id > ? LIMIT 1');
                break;
            default  : return false;
        }
        return true;
    }

    function stream_read()
    {
         $this->_ps->execute(array($this->_rowId));
         if($this->_ps->rowCount() == 0) return false;
         $this->_ps->bindcolumn(1, $this->_rowId);
         $this->_ps->bindcolumn(2, $ret);
         $this->_ps->fetch();
         return $ret;
    }

    function stream_write($data)
    {
        $this->_ps->execute(array($data));
        return strlen($data);
    }

    function stream_tell()
    {
        return $this->_rowId;
    }

    function stream_eof()
    {
        $this->_ps->execute(array($this->_rowId));
        return (bool) $this->_ps->rowCount();
    }

    function stream_seek($offset, $step)
    {
        //No need to be implemented
    }
}

stream_register_wrapper('db', 'DBStream');

$fr = fopen('db://testuser@localhost/testdb', 'r');
$fw = fopen('db://testuser:testpassword@localhost/testdb', 'w');
//The two forms above are accepted : for the former, the default password "" will be used

$alg = hash_algos();
$al = $alg[array_rand($alg)];
$data = hash($al, rand(rand(0, 9), rand(10, 999))); // Some random data to be written
fwrite($fw, $data); // Writing the data to the wrapper
while($a = fread($fr, 256)){ //A loop for reading from the wrapper
    echo $a . '<br />';
}
?>

Hope it helps, cheers ;)

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