Pass DWORD pointer by using 'calllib' to c function

hi,

I'm trying to pass values by using 'calllib' to c function.

The input of the function is a dword pointer,how can i create dword pointer?

p.s I can't change the dll, the code must be on the matlab side.

c:

Counter(DWORD* Packets)

matlab:

my_pointer= libpointer('______'); % here is the question
calllib('c_dll','Counter',my_pointer)

TNX

Answer 1

[Philip Borghesani]

A DWORD is a uint32 in matlab but no libpointer or conversion should be necceary.

You did not give enough information to formulate a full answer but here are some suggestions. A pointer object should not be needed to call this function.

If the function has a return value try:

 [retval, newcounterval]=calllib('c_dll','Counter',0) % or whatever value counter wants as input

If you feel you need a pointer then use:

 my_pointer=libpointer('uint32Ptr',0)
 retval=calllib('c_dll','Counter',my_pointer)
 newcountervalue=my_pointer.value

If you are getting error messages then please let us know what is happening. Frequently use of DWORD by a library requires adding windows.h to the included header or making a new header.

[pavel]

Hi, First of all thanks for the quick response. I can't use the first option, because the c function changes the pointer's value and only returns 'pass' or 'fail' status. The second option worked great. thank you very mutch.

[Philip Borghesani]

The first syntax should still work. the pass fail status will be in retval and the modified counter value will be in newcounterval. If the function continuously modifies the counter after the call then the second syntax is required and the situation is dangerous because the process MUST be stopped before the pointer variable goes out of scope.