ctypes and how to copy data passed to callback

waldek waldemar.rymarkiewicz at gmail.com
Mon Jul 28 15:11:56 CEST 2008


I'm trying  to handle data passed to Py Callback which is called from
C dll. Callback passes data to another thread using Queue module and
there the data are printed out.

If data is printed out in a callback itself  it's ok. If I put on
queue and next get from queue in another thread script prints some
trash. Looks like the data is released when callback returned. I tired
to make d = copy.deepcopy(data), but it does not work - I got nothing.
Any idea why it's happening ?

--------------------- main thread  --------
def callback(data, size):
    myqueue.put((data, size))

mydll = cdll.MyDLL
cbproto = CFUNCTYPE(c_int, POINTER(c_char), c_int)
mycallback = cbproto(callback)


---------------------------------- thread listener

while True:
    data, size = myqueue.get()
    print "***", data[:size]


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