How to access Call Back Functions using *.dll in the Labview?

Question

Hai,
I am Pavan Ram Kumar Somu.
I am new to Labview, currently I am working on MVB Interface.
I need to access the API functions from *.dll file in Labview, as of now , I am doing this with Call function Library node in Labview but it does not support the following data types like
    1. Pointer Arguments(To which memory it points in Labview)
    2. function pointers Arguments
    3 .pointers in structures and pointer structures in structures and many other data types.
Please Answer the below queries also:
1. How to pass pointer arguments to API functions in DLL and how to collect pointer  
    return types from API functions in DLL
2. How to pass structure arguments to API functions in DLL and how to collect structure
    return types from API functions in DLL
3. How to use callback functions(nothing but function pointers) in Labview and how to
    collect callback fuctions return types from API functions in DLL
I need your help while passing these datatypes to API functions in DLL from labview.
Suggest me if there is any other alternative for implementing this task.
I am referencing some examples here:
Examples:
I)
Unsigned short int gf_open_device(void *p_device_config, unsigned long int client_life_sign_timeout, unsigned short int *device_error)
void *p_device_config: How to access/pass these arguments in LabView and to which memory location it points in LabView.
II) #include <windows.h>
     #include <process.h>
     HANDLE rcvEvent0, rcvEvent1;
/* Function call*/
CanGetReceiveEvent(handle[0], &rcvEvent0);
Above is a piece of C code, Now I want to use HANDLE datatype which is windows based, how to use these type in the LABVIEW.
With regards
Pavan Ramu Samu

Answer 1

"Somu" <[email protected]> wrote in message news:[email protected]...
Hai,
I am Pavan Ram Kumar Somu.
&nbsp;
I am new to Labview, currently I am working on MVB Interface.
&nbsp;
I need to access the API functions from *.dll file in Labview, as of now , I am doing this with Call function Library node in Labview but it does not support the following data types like
&nbsp;&nbsp;&nbsp; 1. Pointer Arguments(To which memory it points in Labview)
&nbsp;&nbsp;&nbsp; 2. function pointers Arguments
&nbsp;&nbsp;&nbsp; 3 .pointers in structures and pointer structures in structures and many other data types.
&nbsp;
Please Answer the below queries also:
&nbsp;
1. How to pass pointer arguments to API functions in DLL and how to collect pointer&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp; return types from API functions in DLL
&nbsp;
2. How to pass structure arguments to API functions in DLL and how to collect structure
&nbsp;&nbsp;&nbsp; return types from API functions in DLL
&nbsp;
3. How to use callback functions(nothing but function pointers) in Labview and how to
&nbsp;&nbsp;&nbsp; collect callback fuctions return types from API functions in DLL
&nbsp;
I need your help while passing these datatypes to API functions in DLL from labview.
&nbsp;
Suggest me if there is any other alternative for implementing this task.
&nbsp;
&nbsp;
I am referencing some examples here:
Examples:
I)
Unsigned short int gf_open_device(void *p_device_config, unsigned long int client_life_sign_timeout, unsigned short int *device_error)
&nbsp;
void *p_device_config: How to access/pass these arguments in LabView and to which memory location it points in LabView.
&nbsp;
II) #include &lt;windows.h&gt;
&nbsp;&nbsp;&nbsp;&nbsp; #include &lt;process.h&gt;
&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp; HANDLE rcvEvent0, rcvEvent1;
&nbsp;
/* Function call*/
CanGetReceiveEvent(handle[0], &amp;rcvEvent0);
&nbsp;
Above is a piece of C code, Now I want to use HANDLE datatype which is windows based, how to use these type in the LABVIEW.
&nbsp;
With regardsPavan Ramu Samu
Search the forum (forums.ni.com) for callback, pointer or handle, and you'll find that it is all possible, but not very easy.
e.g.: http://forums.ni.com/ni/board/message?board.id=170&message.id=88974&requireLogin=False
Regards,
Wiebe.