DH_ReadPoint, DH_ReadExistingPoint
DH_ReadPoint,
DH_ReadExistingPoint — read a point from the Cascade DataHub.
Syntax
#include <cogent.h>
ST_STATUS DH_ReadPoint( | IP_hTASK | myself, |
| | PT_pCPOINT | ppoint, |
| | IP_hMSG | hmsg, |
| | ER_hLIST | elist); |
ST_STATUS DH_ReadExistingPoint( | IP_hTASK | myself, |
| | PT_pCPOINT | ppoint, |
| | IP_hMSG | hmsg, |
| | ER_hLIST | elist); |
Arguments
- myself
- The
task handle associated with this task. This should always be
the return value from IP_NserveInit.
- ppoint
- A
pointer to a Cascade DataHub point structure, which must contain at
least name. All other fields in the point
structure should be 0 if this is the first
call on this point, because they will be filled in by this
call. Subsequent calls on the same point do not require
zeroing any fields. If one point structure is used with
several point names, the address field must be zeroed each time
a different name is used in a call to this
function.
- hmsg
- A
handle to a previously allocated message structure (using IP_MsgCreate) providing enough
buffer space to handle the inter-process communication
associated with the DataHub transaction.
- inter
- Process communication associated with
the DataHub transaction.
- elist
- A
return value containing error information. This is unimplemented in this
version, and should be NULL.
Returns
ST_OK on
success, ST_ERROR on failure, or some other
value of ST_STATUS.
Description
This function reads a point from
the DataHub. If the named point does not exist then DH_ReadPoint
will create it on the DataHub with a confidence factor of zero and
DH_ReadExistingPoint
will return the error ST_NO_POINT.
