If the pointer for an overlapped operation is set to NULL, DeviceIoControl will work in a blocked (synchronous) way.
如果重叠操作的指针设为NULL，那么DeviceIoControl将以阻塞(同步)方式工作。
An overlapped operation was successfully initiated and completion will be indicated at a later time.
成功启动一个重叠操作，过后将有完成指示。
An overlapped operation was successfully initiated and completion will be indicated at a later time.
成功启动一个重叠操作，过后将有完成指示。
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