KsWaitCommEvent

The availability of this function depends on what the device supports.

Waits for an event to occur for a specified communications device. The set of events that are monitored by this function is contained in the event mask associated with the device handle.

Syntax

BOOL KsWaitCommEvent(
     HANDLE hFile,
     LPDWORD lpEvtMask,
     LPOVERLAPPED lpOverlapped
);

Parameters

hFile: a handle to the communications device. The KsCreateComm function returns this handle.

lpEvtMask: a pointer to a variable that receives a mask indicating the type of event that occurred. If an error occurs, the value is zero; otherwise, it is one of the following values.

Value	Description
EV_BREAK 0x0040	A break was detected on input.
EV_CTS 0x0008	The CTS (clear-to-send) signal changed state.
EV_DSR 0x0010	The DSR (data-set-ready) signal changed state.
EV_ERR 0x0080	A line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY.
EV_RING 0x0100	A ring indicator was detected.
EV_RLSD 0x0020	The RLSD (receive-line-signal-detect) signal changed state.
EV_RXCHAR 0x0001	A character was received and placed in the input buffer.
EV_RXFLAG 0x0002	The event character was received and placed in the input buffer. The event character is specified in the device's DCB structure, which is applied to a serial port by using the KsSetCommState function.
EV_TXEMPTY 0x0004	The last character in the output buffer was sent.

lpOverlapped: a pointer to an OVERLAPPED structure. This structure is required if hFile was opened with FILE_FLAG_OVERLAPPED.

If hFile was opened with FILE_FLAG_OVERLAPPED, the lpOverlapped parameter must not be NULL. It must point to a valid OVERLAPPED structure. If hFile was opened with FILE_FLAG_OVERLAPPED and lpOverlapped is NULL, the function can incorrectly report that the operation is complete.

If hFile was opened with FILE_FLAG_OVERLAPPED and lpOverlapped is not NULL, KsWaitCommEvent is performed as an overlapped operation. In this case, the OVERLAPPED structure must contain a handle to a manual-reset event object (created by using the CreateEvent function).

If hFile was not opened with FILE_FLAG_OVERLAPPED, KsWaitCommEvent does not return until one of the specified events or an error occurs.

Return value

If the function succeeds, it returns TRUE, otherwise FALSE. To get extended error information, call GetLastError.

Remarks

The KsWaitCommEvent function monitors a set of events for a specified communications resource. To set and query the current event mask of a communications resource, use the KsSetCommMask and KsGetCommMask functions.

If the overlapped operation cannot be completed immediately, the function returns FALSE and the GetLastError function returns ERROR_IO_PENDING, indicating that the operation is executing in the background. When this happens, the system sets the hEvent member of the OVERLAPPED structure to the not-signaled state before KsWaitCommEvent returns, and then it sets it to the signaled state when one of the specified events or an error occurs. The calling process can use one of the wait functions to determine the event object's state and then use KsGetOverlappedResult function to determine the results of the KsWaitCommEvent operation. KsGetOverlappedResult reports the success or failure of the operation, and the variable pointed to by the lpEvtMask parameter is set to indicate the event that occurred.

If a process attempts to change the device handle's event mask by using the KsSetCommMask function while an overlapped KsWaitCommEvent operation is in progress, KsWaitCommEvent returns immediately. The variable pointed to by the lpEvtMask parameter is set to zero.

Example

N/A

Requirements

	RT	Win32
Minimum supported version	4.0	4.0
Header	kscom.h	kscom.h
Library	KsApi_Rtss.lib	ksapi.h