Php/docs/function.eio-read

• PHP Manual
• Eio 函数
• Read from a file descriptor at given offset

eio_read

(PECL eio >= 0.0.1dev)

eio_read — Read from a file descriptor at given offset

说明

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.

参数

fd

Stream, Socket resource, or numeric file descriptor

length

Maximum number of bytes to read.

offset

Offset within the file.

pri

请求的优先级：EIO_PRI_DEFAULT，EIO_PRI_MIN，EIO_PRI_MAX 或 null。如果是 null，pri 将设为 EIO_PRI_DEFAULT。

callback

callback 函数在请求完成时被调用。其应匹配一下原型：

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

data

传递给请求的用户数据。

result

针对请求的结果的值。通常是相应的系统调用返回的值。

req

可选的请求资源，可被 eio_get_last_error() 之类的函数使用。

data

Arbitrary variable passed to callback.

返回值

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

范例

Example #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 writingeio_open($temp_filename, EIO_O_RDWR, NULL,    EIO_PRI_DEFAULT, "my_file_opened_callback", $temp_filename);eio_event_loop();?>

以上例程的输出类似于：

string(5) "34567"

参见

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