(PECL eio >= 0.5.0b)
eio_seek — Repositions the offset of the open file associated with the fd argument to the argument offset according to the directive whence
$fd
, int $offset
, int $whence
[, int $pri = EIO_PRI_DEFAULT
[, callable $callback = NULL
[, mixed $data = NULL
]]] ) : resource
eio_seek() repositions the offset of the open file associated with
stream, Socket resource, or file descriptor specified by fd to the argument offset according to the directive whence as follows:
EIO_SEEK_SET - Set position equal to offset bytes.EIO_SEEK_CUR - Set position to current location plus offset.EIO_SEEK_END - Set position to end-of-file plus offset.fdStream, Socket resource, or numeric file descriptor
offsetStarting point from which data is to be read.
lengthNumber 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.
eio_seek() returns request resource on success or FALSE on error.