receive bitfield

[Kito]

Hi GerdW!

The prototype of the function i am calling is like this:

void ExampleFunction(int inputA, int inputB, myType output);

The type "myType" is like this:

typedef struct

{

     int a :4;

     int b :8;

     int c :4;

} myType;

It means the type "myType" is 16 bit long (because of the bitfields).

if I define it without the bitfields, it looks like the struct below:

typedef struct

{

     int a;

     int b;

     int c;

} myType;

In this case the type "myType" is 48 bit long, considering int = 16bit.

When I use the type "myType" without bitfields, LabView can build the shared lib call functio.

When I use the struct with bitfields, LabView can't build the shared lib call function.

Then, it is clear that LabView is not being able to handle the bitfields.

So, i am trying to find a way to make LabView handle the "myType" with bitfields, because this is the output of the DLL.

[GerdW]

Hi kito,

it seems you know more about C than me Today I learnt how to define a bitfield...

Ok, serious: how is C storing those bitfields?

When it packs together all the bits you can use my approach from message 4 - you just receive a U16. When it uses single ints with just limited number of bits you can still access them seperately by LabView.

All you need to know is how your C compiler is storing the bitfields in memory. Then mimic that memory layout by a LabView cluster (or a single int, if possible) and you're done...

Message Edited by GerdW on 11-02-2009 04:29 PM

[Kito]

Hi GerdW,

The Labview cannot create a cluster like that. Do you have any alternative for the cluster?

Regards

Kito

[GerdW]

Hi kito,

"It means the type "myType" is 16 bit long (because of the bitfields)."

Use a U16! And the code from message 4...

[Kito]

Hi GerdW, I tryed to that but the Labview cannot recognize the bitfields......and as I told you the code can't be changed.

In my opinion the Labview can't handle in a low level (bit). Otherwise the wizard would have succeeded to do that.

Anyway......thanks for your helping

Regards

Kito

[RavensFan]

I'll step in and ask ...

What if you wrap the call to this dll with another dll that reconstructs the inputs and outputs into datatypes that LV can call?

[Kito]

that's the way I will do......But I really would like that Labview could handle bitfields.....

Again, thanks for you helping

Regards

Kito

[GerdW]

Hi kito,

have you only tried the wizard or really tried to receive an U16? No, LabView doesn't recognize the bitfields - it's your turn to get the needed bits from the U16 (as shown in message 4).

Otherwise try Raven'sFan suggestion!

Message Edited by GerdW on 11-02-2009 10:05 PM

[Kito]

Hi GerdW,

I tryed both and I couldn't have success on that.

By the way, Where is the Reaven's approach?

Regards

Kito

[GerdW]

Hi kito,

read message 16.

Make a wrapper that splits your bitfield into 3 seperate outputs...

Btw. what is "no success"? LV crashing? Not expected output? Have you examined the output in binary display?

Message Edited by GerdW on 11-02-2009 10:13 PM