title: Python ctypes and function pointers
body: <p>This is related to <a href="https://stackoverflow.com/questions/867850/creating-a-wrapper-for-a-c-library-in-python">my other question</a>, but I felt like I should ask it in a new question.</p>
  
  <p>Basically FLAC uses function pointers for callbacks, and to implement callbacks with ctypes, you use <code>CFUNCTYPE</code> to prototype them, and then you use the <code>prototype()</code> function to create them. </p>
  
  <p>The problem I have with this is that I figured that I would create my callback function as such (I am not showing the structures that I have recreated, FLAC__Frame is a Structure):</p>
  
  <pre><code>write_callback_prototype = CFUNCTYPE(c_int, c_void_p, 
                                       POINTER(FLAC__Frame), 
                                       POINTER(c_int32), v_void_p)</code></pre>
  
  <p>The problem that I have is the implementation. FLAC__Frame is never instantiated by the programmer, it's only called from from the initialization function, and the processing functions.I have to write the callback function myself, but he problem is that I don't know how I would do this, so if anyone knows how I should do this, then some help would be greatly appreciated.</p>