Purpose
Check if data was returned from a previously
issued AsyncRead API. This API can be issued multiple times
for a single AsyncRead call. It will return 0 when the
data actually has been returned.
Syntax
unsigned int CWB_ENTRY cwbDQ_CheckData(
cwbDQ_ReadHandle readHandle,
cwbSV_ErrHandle errorHandle);
Parameters
- cwbDQ_ReadHandle readHandle - input
- The handle that was returned by the AsyncRead API.
- cwbSV_ErrHandle errorHandle - output
- Any returned messages will be written to this object. It is created with
the cwbSV_CreateErrHandle API. The messages may be retrieved
through the cwbSV_GetErrText API. If the parameter is set
to zero, no messages will be retrieved.
Return Codes
The following list shows common return
values.
- CWB_OK
- Successful completion.
- CWBDQ_INVALID_READ_HANDLE
- Invalid read handle.
- CWBDQ_DATA_TRUNCATED
- Data truncated.
- CWBDQ_TIMED_OUT
- Wait time expired and no data returned.
- CWBDQ_REJECTED_USER_EXIT
- Command rejected by user exit program.
- CWBDQ_QUEUE_DESTROYED
- Queue was destroyed.
- CWBDQ_NO_DATA
- No data.
- CWBDQ_CANNOT_CONVERT
- Unable to convert data.
Usage
This function requires that you have previously
issued the following APIs:
- cwbDQ_Open or cwbDQ_OpenEx
- cwbDQ_CreateData
- cwbDQ_AsyncRead
If a time limit was specified on the AsyncRead,
this API will return CWBDQ_NO_DATA until data is returned (return code will
be CWB_OK), or the time limit expires (return code will be CWBDQ_TIMED_OUT).