Perform file readahead into page cache

说明

resource eio_readahead ( mixed $fd , int $offset , int $length [, int $pri = EIO_PRI_DEFAULT [, callable $callback = NULL [, mixed $data = NULL ]]] )

eio_readahead() populates the page cache with data from a file so that subsequent reads from that file will not block on disk I/O. See READAHEAD(2) man page for details.

参数

fd

Stream, Socket resource, or numeric file descriptor

offset

Starting point from which data is to be read.

length

Number of bytes to be read.

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_readahead() returns request resource on success or FALSE on error.