How to invoke kernel32.SetWaitableTimer

Python Help
1

Hi, I get a problem by using python invoke windows kernel32.Setwaitable, it don’t call back my python function, how to simulate
PTIMERAPCROUTINE param.

the microsoft doc:

my code:

test py:
unitree_sdk2py/test/platform/test_timerfd.py

2

Here are a few of the mistakes in your code:

  • wintypes.LARGE_INTEGER is defined as a ctypes.c_longlong simple type, not a WinAPI LARGE_INTEGER structure. It thus doesn’t have a QuadPart attribute, and assigning a dynamic QuadPart attribute isn’t used by anything.
  • The timer callback function has to be kept alive by a reference. You can’t just create and assign it in a function scope that no longer exists when the system tries to call it.
  • The callback function gets queued to the thread’s APC (asynchronous procedure call) queue as a non-special APC. The system only executes non-special APCs when a thread signals that it’s in an alertable state via SleepEx() or a wait function such as WaitForSingleObjectEx(). Your code uses a non-alertable wait via WaitForSingleObject().

Here’s some code that demonstrates using a waitable timer.

import ctypes from ctypes import wintypes kernel32 = ctypes.WinDLL('kernel32', use_last_error=True) INFINITE = wintypes.DWORD(-1).value WAIT_FAILED = wintypes.DWORD(-1).value WAIT_IO_COMPLETION = 192 # https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nc-synchapi-ptimerapcroutine PTIMERAPCROUTINE = ctypes.WINFUNCTYPE( None, # no return value wintypes.LPVOID, # lpArgToCompletionRoutine wintypes.DWORD, # dwTimerLowValue wintypes.DWORD, # dwTimerHighValue ) # https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-createwaitabletimerw kernel32.CreateWaitableTimerW.restype = wintypes.HANDLE kernel32.CreateWaitableTimerW.argtypes = ( wintypes.LPVOID, # lpTimerAttributes wintypes.BOOL, # bManualReset wintypes.LPCWSTR, # lpTimerName ) # https://learn.microsoft.com/zh-cn/windows/win32/api/synchapi/nf-synchapi-setwaitabletimer kernel32.SetWaitableTimer.restype = wintypes.BOOL kernel32.SetWaitableTimer.argtypes = ( wintypes.HANDLE, # hTimer wintypes.PLARGE_INTEGER, # lpDueTime wintypes.LONG, # lPeriod PTIMERAPCROUTINE, # pfnCompletionRoutine, wintypes.LPVOID, # lpArgToCompletionRoutine wintypes.BOOL, # fResume ) # https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-cancelwaitabletimer kernel32.CancelWaitableTimer.restype = wintypes.BOOL kernel32.CancelWaitableTimer.argtypes = ( wintypes.HANDLE, # hTimer ) # https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-waitforsingleobjectex kernel32.WaitForSingleObjectEx.restype = wintypes.DWORD kernel32.WaitForSingleObjectEx.argtypes = ( wintypes.HANDLE, # hHandle wintypes.DWORD, # dwMilliseconds wintypes.BOOL, # bAlertable ) #https://learn.microsoft.com/en-us/windows/win32/api/handleapi/nf-handleapi-closehandle kernel32.CloseHandle.restype = wintypes.BOOL kernel32.CloseHandle.argtypes = ( wintypes.HANDLE, # hObject ) 
@PTIMERAPCROUTINE def timer_callback(arg, timer_low, timer_high): print(f'CALLBACK: {timer_low / 1e7:.2f}') def timer_init(due_time: float, period: float) -> int: due_time = wintypes.LARGE_INTEGER(-int(due_time * 10**7)) period = int(period * 1000) handle = kernel32.CreateWaitableTimerW(None, True, None) if not handle: raise ctypes.WinError(ctypes.get_last_error()) if not kernel32.SetWaitableTimer( handle, ctypes.byref(due_time), period, timer_callback, 0, True): kernel32.CloseHandle(handle) raise ctypes.WinError(ctypes.get_last_error()) return handle def test(count): h = timer_init(1, 5) try: for i in range(count * 2): result = kernel32.WaitForSingleObjectEx(h, INFINITE, True) if result == 0: print('WAIT: Successful') elif result == WAIT_IO_COMPLETION: print('WAIT: APC Executed\n') elif result == WAIT_FAILED: raise ctypes.WinError(ctypes.get_last_error()) else: raise OSError(f'Unexpected wait result: {result}') finally: kernel32.CancelWaitableTimer(h) kernel32.CloseHandle(h)

Example:

>>> test(3) WAIT: Successful CALLBACK: 64.10 WAIT: APC Executed WAIT: Successful CALLBACK: 69.11 WAIT: APC Executed WAIT: Successful CALLBACK: 74.12 WAIT: APC Executed
1 Like
3

thank for your help. Let me discover my mistake