eio_readahead

(PECL eio >= 0.0.1dev)

eio_readahead — Perform file readahead into page cache

說明

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

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.

參數(shù)

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

請(qǐng)求的優(yōu)先級(jí)：EIO_PRI_DEFAULT，EIO_PRI_MIN，EIO_PRI_MAX 或 null。如果是 null，pri 將設(shè)為 EIO_PRI_DEFAULT。

callback

callback 函數(shù)在請(qǐng)求完成時(shí)被調(diào)用。其應(yīng)匹配一下原型：

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

傳遞給請(qǐng)求的用戶數(shù)據(jù)。

result

針對(duì)請(qǐng)求的結(jié)果的值。通常是相應(yīng)的系統(tǒng)調(diào)用返回的值。

req

可選的請(qǐng)求資源，可被 eio_get_last_error() 之類的函數(shù)使用。

data

Arbitrary variable passed to callback.

返回值

eio_readahead() returns request resource on success, 或者在失敗時(shí)返回 false.