如何获得与python ctypes一起用作回调的方法？ [英] How can I get methods to work as callbacks with python ctypes?

问题描述

我有一个C api与python ctypes软件包连接。

I have an C api that i'm interfacing with the python ctypes package. Everything works well, except this little tidbit.

要将功能注册为某些通知的回调，我称这个功能为：

To register functions as callbacks to some notifications, i call this function :

void RegisterNotifyCallback( int loginId, int extraFlags, void *(*callbackFunc)(Notification *))

因此在python中，我的代码如下：

so in python my code looks like :

CALLBACK = ctypes.CFUNCTYPE(None, ctypes.POINTER(Notification))
func = CALLBACK(myPythonCallback)
myLib.RegisterNofityCallback(45454, 0, func)

如果myPythonCallback的值是FunctionType（即不是方法），则可以正常工作并使用正确的参数调用回调函数。如果它是MethodType，它仍然会调用该方法，但是一旦该方法完成，就会出现段错误。

If the value of myPythonCallback is a FunctionType (i.e. not a method), it works fine and calls the callback function with the correct parameters. If it's a MethodType, it still calls the method but then blows up with a segfault once the method is finished.

edit

为了澄清，当我说函数类型时，我的意思是myPythonCallback被定义为一个函数，

To clarify, when i say function type i mean that myPythonCallback is defined as a function,

def myPythonCallback(Notification):
    ...do something with the Notification object i get passed in

$ b中传递$ b

当我说它是一个MethodType时，我的意思是一个类方法：

When i say it's a MethodType, i mean a class method :

class MyClass(object):
    def myPythonCallback(self, Notification):
        ...do something with Notification

这附近容易吗？或者有人可以向我解释为什么会发生这种情况？

Is there an easy away around this ? Or can someone offer me an explanation as to why this is happening ?

非常感谢，
Al。

Many thanks, Al.

edit

与GDB进一步挖掘可以使我做到这一点：

Digging a bit further with GDB gives me this :

Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 1544567712 (LWP 5389)] 0x555ae962 in instancemethod_dealloc (im=0x558ed644) at Objects/classobject.c:2360 2360    Objects/classobject.c: No such file or directory.
        in Objects/classobject.c (gdb) backtrace
#0  0x555ae962 in instancemethod_dealloc (im=0x558ed644) at Objects/classobject.c:2360
#1  0x555f6a61 in tupledealloc (op=0x5592010c) at Objects/tupleobject.c:220
#2  0x555aeed1 in instancemethod_call (func=0x558db8ec, arg=0x5592010c, kw=0x0) at Objects/classobject.c:2579
#3  0x5559aedb in PyObject_Call (func=0x558db8ec, arg=0x5592c0ec, kw=0x0) at Objects/abstract.c:2529
#4  0x5563d5af in PyEval_CallObjectWithKeywords (func=0x558db8ec, arg=0x5592c0ec, kw=0x0) at Python/ceval.c:3881
#5  0x5559ae6a in PyObject_CallObject (o=0x0, a=0x0) at Objects/abstract.c:2517

并且传递给instancemethod_dealloc的值是：

and the value passed into instancemethod_dealloc is :

(gdb) x 0x558ed644 0x558ed644:     0x00000000

您认为这是可以解决的吗？

Do you reckon this is fixable ?

推荐答案

据我所知，您不能调用绑定方法，因为它缺少sel f参数。我使用闭包来解决此问题，如下所示：

You can't, so far as I know, call a bound method because it is missing the self parameter. I solve this problem using a closure, like this:

CALLBACK = ctypes.CFUNCTYPE(None, ctypes.POINTER(Notification))

class MyClass(object):

    def getCallbackFunc(self):
        def func(Notification):
            self.doSomething(Notification)
        return CALLBACK(func)

    def doRegister(self):
        myLib.RegisterNofityCallback(45454, 0, self.getCallbackFunc())

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