串口设备驱动相关事件的掩码定义（IOCTL_SERIAL_GET_WAIT_MASK）

     最近研究网口转虚拟串口驱动程序。通过查看DDK的例子，发现需要处理 IOCTL_SERIAL_GET_WAIT_MASK 。但是一些相关的掩码定义比较少见到，相关的资料说明也少。这里列举出来，以便自己更好的理解，同时用于编写的虚拟串口驱动程序中。

     相关掩码的定义在 C:\WinDDK\7600.16385.1\inc\api\ntddser.h 文件中。 原本的内容注释已经非常清晰了，我就不画蛇添足了。

//
// Defines the bitmask that the driver can used to notify
// app of various changes in the state of the UART.
//

#define SERIAL_EV_RXCHAR           0x0001  // Any Character received
#define SERIAL_EV_RXFLAG           0x0002  // Received certain character
#define SERIAL_EV_TXEMPTY          0x0004  // Transmitt Queue Empty
#define SERIAL_EV_CTS              0x0008  // CTS changed state
#define SERIAL_EV_DSR              0x0010  // DSR changed state
#define SERIAL_EV_RLSD             0x0020  // RLSD changed state
#define SERIAL_EV_BREAK            0x0040  // BREAK received
#define SERIAL_EV_ERR              0x0080  // Line status error occurred
#define SERIAL_EV_RING             0x0100  // Ring signal detected
#define SERIAL_EV_PERR             0x0200  // Printer error occured
#define SERIAL_EV_RX80FULL         0x0400  // Receive buffer is 80 percent full
#define SERIAL_EV_EVENT1           0x0800  // Provider specific event 1
#define SERIAL_EV_EVENT2           0x1000  // Provider specific event 2