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stream_register_wrapper

(PHP 4 >= 4.3.0)

stream_register_wrapper -- Register a URL wrapper implemented as a PHP class

Description

boolean stream_register_wrapper ( string protocol, string classname)

stream_register_wrapper() allows you to implement your own protocol handlers and streams for use with all the other filesystem functions (such as fopen(), fread() etc.).

To implement a wrapper, you need to define a class with a number of member functions, as defined below. When someone fopens your stream, PHP will create an instance of classname and then call methods on that instance. You must implement the methods exactly as described below - doing otherwise will lead to undefined behaviour.

stream_register_wrapper() will return FALSE if the protocol already has a handler.

boolean stream_open ( string path, string mode, int options, string opened_path)

This method is called immediately after your stream object is created. path specifies the URL that was passed to fopen() and that this object is expected to retrieve. You can use parse_url() to break it apart.

mode is the mode used to open the file, as detailed for fopen(). You are responsible for checking that mode is valid for the path requested.

options holds additional flags set by the streams API. It can hold one or more of the following values OR'd together.

FlagDescription
STREAM_USE_PATHIf path is relative, search for the resource using the include_path.
STREAM_REPORT_ERRORSIf this flag is set, you are responsible for raising errors using trigger_error() during opening of the stream. If this flag is not set, you should not raise any errors.

If the path is opened successfully, and STREAM_USE_PATH is set in options, you should set opened_path to the full path of the file/resource that was actually opened.

If the requested resource was opened successfully, you should return TRUE, otherwise you should return FALSE

void stream_close ( void )

This method is called when the stream is closed, using fclose(). You must release any resources that were locked or allocated by the stream.

string stream_read ( int count)

This method is called in response to fread() and fgets() calls on the stream. You must return up-to count bytes of data from the current read/write position as a string. If there are less than count bytes available, return as many as are available. If no more data is available, return either FALSE or an empty string. You must also update the read/write position of the stream by the number of bytes that were successfully read.

int stream_write ( string data)

This method is called in response to fwrite() calls on the stream. You should store data into the underlying storage used by your stream. If there is not enough room, try to store as many bytes as possible. You should return the number of bytes that were successfully stored in the stream, or 0 if none could be stored. You must also update the read/write position of the stream by the number of bytes that were successfully written.

boolean stream_eof ( void )

This method is called in response to feof() calls on the stream. You should return TRUE if the read/write position is at the end of the stream and if no more data is available to be read, or FALSE otherwise.

int stream_tell ( void )

This method is called in response to ftell() calls on the stream. You should return the current read/write position of the stream.

boolean stream_seek ( int offset, int whence)

This method is called in response to fseek() calls on the stream. You should update the read/write position of the stream according to offset and whence. See fseek() for more information about these parameters. Return TRUE if the position was updated, FALSE otherwise.

boolean stream_flush ( void )

This method is called in response to fflush() calls on the stream. If you have cached data in your stream but not yet stored it into the underlying storage, you should do so now. Return TRUE if the cached data was successfully stored (or if there was no data to store), or FALSE if the data could not be stored.

The example below implements a var:// protocol handler that allows read/write access to a named global variable using standard filesystem stream functions such as fread(). The var:// protocol implemented below, given the url "var://foo" will read/write data to/from $GLOBALS["foo"].

Ejemplo 1. A Stream for reading/writing global variables

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;
        }
    }
}

stream_register_wrapper("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);

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