If a function needs to maintain the state of some data over successive calls, such as a working buffer or a pointer, the caller should provide this data.
如果函数需要在一系列调用期间维持某些数据的状态，比如工作缓存或指针，那么调用者应该提供此数据。
Because the state of the internal buffer is FULL, the available data is returned and a notify issued.
因为内部缓冲的状态是FULL，所以可用数据将被返回，并发出一个notify 。
As we know, we also need to add a sequence number and a state (IOType variable, IOZeroReadCompleted, etc.) to our buffer.
众所周知，我们也需要添加序号和状态(IOType变量，IOZeroReadCompleted，等等)到我们的缓冲中。
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