eio_read

(PECL eio >= 0.0.1dev)

eio_read — Read from a file descriptor at given offset

Beschreibung

eio_read(
    mixed $fd,
    int $length,
    int $offset,
    int $pri,
    callable $callback,
    mixed $data = NULL
): resource

eio_read() reads up to length bytes from fd file descriptor at offset. The read bytes are stored in result argument of callback.

Parameter-Liste

fd

Stream, Socket resource, or numeric file descriptor

length

Maximum number of bytes to read.

offset

Offset within the file.

pri

The request priority: EIO_PRI_DEFAULT, EIO_PRI_MIN, EIO_PRI_MAX, or null. If null passed, pri internally is set to EIO_PRI_DEFAULT.

callback

Die callback-Funktion wird aufgerufen, wenn die Anfrage abgeschlossen ist. Sie muss dem folgenden Prototyp entsprechen:

void callback(mixed $data, int $result[, resource $req]);

data: sind die benutzerdefinierten Daten, die an die Anfrage übergeben werden.
result: der anfragespezifische Ergebniswert; im Grunde der Wert, der vom entsprechenden Systemaufruf zurückgegeben wird.
req: ist eine optionale Anfrage-Ressource, die in Funktionen wie eio_get_last_error() verwendet werden kann

data

Arbitrary variable passed to callback.

Rückgabewerte

eio_read() stores read bytes in result argument of callback function.

Beispiele

Beispiel #1 eio_read() example

<?php
// Open a temporary file and write some bytes there
$temp_filename = "eio-temp-file.tmp";
$fp = fopen($temp_filename, "w");
fwrite($fp, "1234567890");
fclose($fp);

/* Is called when eio_read() is done */
function my_read_cb($data, $result) {
    global $temp_filename;

 // Output read bytes
    var_dump($result);

 // Close file
    eio_close($data);
    eio_event_loop();

 // Remove temporary file
    @unlink($temp_filename);
}

/* Is called when eio_open() is done */
function my_file_opened_callback($data, $result) {
 // $result should contain the file descriptor
    if ($result > 0) {
  // Read 5 bytes starting from third
        eio_read($result, 5, 2, EIO_PRI_DEFAULT, "my_read_cb", $result);
        eio_event_loop();
    } else {
  // eio_open() failed
        unlink($data);
    }
}

// Open the file for reading and writing
eio_open($temp_filename, EIO_O_RDWR, NULL,
    EIO_PRI_DEFAULT, "my_file_opened_callback", $temp_filename);
eio_event_loop();
?>

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

string(5) "34567"

Siehe auch

eio_open() - Opens a file
eio_write() - Write to file
eio_close() - Close file
eio_event_loop() - Polls libeio until all requests proceeded

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