(PECL event >= 1.2.6-beta)
EventBuffer::expand — Reserves space in buffer
$len
): bool
Alters the last chunk of memory in the buffer, or adds a new chunk, such
that the buffer is now large enough to contain
len
bytes without any further allocations.
len
The number of bytes to reserve for the buffer
成功时返回 true， 或者在失败时返回 false。