Call CFUNCTYPE, class Structure, ctype, dll and Callback function problem
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From: legard_new on 31 Jul 2010 15:09 Hello, I have a problem with calling Callback function with Python. I have a DLL file. Below is a description in documentation. FUNCTION Callback Arguments: Callback ID integer read-only, immediate value CBackProc address read-only, immediate value Returns: status The Callback routine registers the callback routine for notification of a link state change. The callback procedure provided by the application must accept one parameter: the address of the structure containing the data. CallbackID An integer identifying the callback routine being provided to the API. Can be one of 1 or 2. CBackProc The address of the callback procedure that the API will execute. This procedure must accept one parameter, of type LinkStateStruct, passed by reference. LinkStateStruct read-only, by reference OldState: byte NewState byte The routine will return one of the following error codes: 1 - The callback address was successfully registered by the API. 2 - The API has not been initialised. 3 - The CallbackID value was not recognised as a valid link state callback. Here is my little code in Python: from ctypes import * class LinkStateStruct(Structure): _fields_ = [("OldState", c_byte), ("NewState", c_byte)] demoapi=windll.LoadLibrary("D:\\DEMO.dll") #DECLARE CALLBACK FUNCTION g_HLSC = CFUNCTYPE(c_int, POINTER(LinkStateStruct)) def py_g_HLSC(x): print "CALLBACK__py_g_HLSC_FIRED->", x return 0 g__HLSC = g_HLSC(py_g_HLSC) status=demoapi.Callback(1,g__HLSC) print "Status=",status My result is: Status= 1 But Callback function is not executed. If think that i call g__HLSC witohout paramter that in document "The callback procedure provided by the application must accept one parameter: the address of the structure containing the data.". I don't now how to do. Please help. Best regards, Gregory
From: legard_new on 1 Aug 2010 02:42
On Jul 31, 10:22 pm, "Mark Tolonen" <metolone+gm...(a)gmail.com> wrote: > "legard_new" <legar...(a)gmail.com> wrote in message > > news:70faf0b4-fead-49ac-bf18-e182fd63bbff(a)j8g2000yqd.googlegroups.com... > > > > > > > Hello, > > > I have a problem with calling Callback function with Python. I have a > > DLL file. > > > Below is a description in documentation. > > FUNCTION Callback > > Arguments: Callback ID integer read-only, immediate value > > CBackProc address read-only, immediate value > > Returns: status > > The Callback routine registers the callback routine for > > notification of a link state change. > > The callback procedure provided by the application must accept one > > parameter: > > the address of the structure containing the data. > > > CallbackID An integer identifying the callback routine being > > provided to the API. Can be one of 1 or 2. > > CBackProc The address of the callback procedure that the API will > > execute. > > > This procedure must accept one parameter, of type LinkStateStruct, > > passed by reference. > > > LinkStateStruct read-only, by reference > > OldState: byte > > NewState byte > > > The routine will return one of the following error codes: > > 1 - The callback address was successfully registered by the API. > > 2 - The API has not been initialised. > > 3 - The CallbackID value was not recognised as a valid link state > > callback. > > > Here is my little code in Python: > > > from ctypes import * > > class LinkStateStruct(Structure): > > _fields_ = [("OldState", c_byte), > > ("NewState", c_byte)] > > demoapi=windll.LoadLibrary("D:\\DEMO.dll") > > #DECLARE CALLBACK FUNCTION > > g_HLSC = CFUNCTYPE(c_int, POINTER(LinkStateStruct)) > > def py_g_HLSC(x): > > print "CALLBACK__py_g_HLSC_FIRED->", x > > return 0 > > g__HLSC = g_HLSC(py_g_HLSC) > > status=demoapi.Callback(1,g__HLSC) > > print "Status=",status > > > My result is: > > Status= 1 > > > But Callback function is not executed. If think that i call g__HLSC > > witohout paramter that in document "The callback procedure > > > provided by the application must accept one parameter: the address of > > the structure containing the data.". I don't now how to do. > > I don't see anything wrong with your declarations. It indicates you > registered the callback successfully. Since the callback sounds like it > monitors changes in "link state" maybe it isn't changing. Perhaps you need > to call another function that causes this change. > > Here's a DLL I wrote to test your code, but I added a ChangeLinkState > function. When I call it after running your code the callback gets called, > so your code is working properly. > > (Compiled with Visual Studio 2008 "cl /MD /LD demo.c" > > typedef unsigned char BYTE; > > typedef struct tagLINKSTATE { > BYTE OldState, NewState; > > } LINKSTATE; > > typedef int (*CB)(LINKSTATE*); > > CB g_cb; > BYTE g_linkState; > > __declspec(dllexport) int __stdcall Callback(int a,CB cb) > { > g_cb = cb; > return 1; > > } > > __declspec(dllexport) void __stdcall ChangeLinkState(BYTE newState) > { > LINKSTATE state; > state.OldState = g_linkState; > state.NewState = newState; > g_linkState = newState; > g_cb(&state); > > } > > -Mark Thanks Mark for good news. >> Perhaps you need to call another function that causes this change. Exactly, i check again documentation and i must call another functions. Thanks for help. Best regards, Gregory |