> ----------------------------------------------------------------------------
> long initialise(unsigned char *Num, Config **cfg, List *alarms);
> ----------------------------------------------------------------------------
>
> Where the structures are defined as follows:
>
> ---------------------------------------
> struct Config
> {
> unsigned char sensor_id;
> unsigned short offset_time;
> double sample_rate;
> unsigned short buffer_len;
> } ;
> --------------------------------------------
> struct List
> {
> CAlarm *alarms[255];
> } ;
> ------------------------------------------------
> struct CAlarm
> {
> TimeStamp time_stamp;
> unsigned char src_channel
> char area[255];
> unsigned char priority;
> char msg[255];
> } ;
> ----------------------------------------------------
I'm having to make some guesses here since I don't have the full
documentation or even the full API. It look like the DLL intends to
return a pointer to the Config struct, either you are supposed to call
back later to release it, or it is static storage that you just share
with the DLL.
LV data is pretty dynamic and LV wants to have allocated all of the data
that its generated code affects. This is in part due to the scheduling
that goes on to execute, and partly to simplify things. If you write a
wrapper DLL that takes that pointer and copies the fields into a LV
cluster passed into the wrapper by Adapt To Type, then LV will be happier.
The last parameter looks like something you are supposed to allocate
storage for and the DLL will fill in. It also causes some difficulty
since LV currently use handles for nested allocations and it looks like
the List is 255 pointers to a struct. A LV array of clusters will have
the CAlarm info inline and an array of arrays will look like 255
pointers to pointers to structs. If you have access to the C code, you
can look at introducing an initialise2 function with a more LV friendly
function signature, or you can build that in the wrapper DLL. For the
second one, I'd make an array of clusters. In the cluster put a
timestamp, whatever that is, followed by the u8, then a cluster of 255
u8s, then a u8, then a cluster of 255 u8s. Initialize the array to be
255 elements big and call the wrapper. In the wrapper, make a stack
based array of pointers to the LV clusters and send that to the original
DLL. The DLL will automatically write into the LV clusters so there is
nothing to do on the way back out of the DLL.
Also, determine if the storage of the Config needs to be freed later and
arrange for that to happen. You may need to return the pointer to LV as
an int32 and pass it in to a later DLL call for release.
Greg McKaskle
