From: Leandro Lucarella Date: Tue, 13 Nov 2007 00:58:04 +0000 (-0300) Subject: Support general signals handling in EventLoop. X-Git-Url: https://git.llucax.com/software/pymin.git/commitdiff_plain/9b74460c463eaeb6cc6573ee9e7309f91fafd20c?ds=sidebyside Support general signals handling in EventLoop. Now the EventLoop has no support for timers but have general signals handling support. Signals to be handled can be specified in the constructor or by calling set_signal() method. Stop handling a particular type of signals is supported too by calling to the unset_signal() method. A callback can be specified for each type of signal, or all signal handling can be done in the handle_signal() method, if overriden by EventLoop subclasses. --- diff --git a/pymin/eventloop.py b/pymin/eventloop.py index 86b8932..fe3c4ec 100644 --- a/pymin/eventloop.py +++ b/pymin/eventloop.py @@ -37,16 +37,16 @@ class LoopInterruptedError(RuntimeError): r"str(obj) -> String representation." return 'Loop interrupted: %s' % self.select_error -# Flag to know if a timer was expired -timeout = False +# Flag to know if a signal was caught +signals = list() # Alarm Signal handler -def alarm_handler(signum, stack_frame): - global timeout - timeout = True +def signal_handler(signum, stack_frame): + global signals + signals.append(signum) class EventLoop: - r"""EventLoop(file[, timer[, handler[, timer_handler]]]) -> EventLoop. + r"""EventLoop(file[, handler[, signals]]]) -> EventLoop. This class implements a simple event loop based on select module. It "listens" to activity a single 'file' object (a file, a pipe, @@ -54,8 +54,11 @@ class EventLoop: function (or the handle() method if you prefer subclassing) every time the file is ready for reading (or has an error). - If a 'timer' is supplied, then the timer_handler() function object - (or the handle_timer() method) is called every 'timer' seconds. + 'signals' is a dictionary with signals to be handled by the loop, + where keys are signal numbers and values are callbacks (which takes + 2 arguments, first the event loop that captured the signal, and then + the captured signal number). Callbacks can be None if all signals + are handled by the handle_signal() member function. This is a really simple example of usage using a hanlder callable: @@ -75,20 +78,19 @@ class EventLoop: >>> class Test(EventLoop): >>> def handle(self): >>> data = os.read(self.fileno, 100) - >>> if data == 'q\n': - >>> self.stop() - >>> else: - >>> os.write(1, 'Received message: %r\n' % data) - >>> def handle_timer(self): - >>> print time.strftime('%c') - >>> p = Test(0, timer=5) + >>> os.write(1, 'Received message: %r\n' % data) + >>> def handle_signal(self, signum): + >>> os.write(1, 'Signal %d received, stopping\n' % signum) + >>> self.stop() + >>> p = Test(0, signals={signal.SIGTERM: None, signal.SIGINT: None}) >>> p.loop() - This example loops until the user enters a single "q", when stop() - is called and the event loop is exited. + This example loops until the user enter interrupts the program (by + pressing Ctrl-C) or untile the program is terminated by a TERM signal + (kill) when stop() is called and the event loop is exited. """ - def __init__(self, file, handler=None, timer=None, timer_handler=None): + def __init__(self, file, handler=None, signals=None): r"""Initialize the EventLoop object. See EventLoop class documentation for more info. @@ -96,15 +98,35 @@ class EventLoop: self.poll = select.poll() self._stop = False self.__register(file) - self.timer = timer self.handler = handler - self.timer_handler = timer_handler + self.signals = dict() + if signals is None: + signals = dict() + for (signum, sighandler) in signals.items(): + self.set_signal(signum, sighandler) def __register(self, file): r"__register(file) -> None :: Register a new file for polling." self._file = file self.poll.register(self.fileno, POLLIN | POLLPRI | POLLERR) + def set_signal(self, signum, sighandler): + prev = self.signals.get(signum, None) + # If the signal was not already handled, handle it + if signum not in self.signals: + signal.signal(signum, signal_handler) + self.signals[signum] = sighandler + return prev + + def get_signal_handler(self, signum): + return self.signals[signum] + + def unset_signal(self, signum): + prev = self.signals[signum] + # Restore the default handler + signal.signal(signum, signal.SIG_DFL) + return prev + def set_file(self, file): r"""set_file(file) -> None :: New file object to be monitored @@ -142,40 +164,35 @@ class EventLoop: Wait for events and handle then when they arrive. If once is True, then only 1 event is processed and then this method returns. """ - # Flag modified by the signal handler - global timeout - # If we use a timer, we set up the signal - if self.timer is not None: - signal.signal(signal.SIGALRM, alarm_handler) - self.handle_timer() - signal.alarm(self.timer) + # List of pending signals + global signals while True: try: res = self.poll.poll() except select.error, e: - # The error is not an interrupt caused by the alarm, then raise - if e.args[0] != errno.EINTR or not timeout: + # The error is not an interrupt caused by a signal, then raise + if e.args[0] != errno.EINTR or not signals: raise LoopInterruptedError(e) - # There was a timeout, so execute the timer handler - if timeout: - timeout = False - self.handle_timer() - signal.alarm(self.timer) - # Not a timeout, execute the regular handler - else: + # If we have signals to process, we just do it + have_signals = bool(signals) + while signals: + self.handle_signal(signals.pop(0)) + # No signals to process, execute the regular handler + if not have_signals: self.handle() + import os # Look if we have to stop if self._stop or once: self._stop = False break def handle(self): - r"handle() -> None :: Abstract method to be overriden to handle events." + r"handle() -> None :: Handle file descriptor events." self.handler(self) - def handle_timer(self): - r"handle() -> None :: Abstract method to be overriden to handle events." - self.timer_handler(self) + def handle_signal(self, signum): + r"handle_signal(signum) -> None :: Handles signals." + self.signals[signum](self, signum) if __name__ == '__main__': @@ -195,16 +212,14 @@ if __name__ == '__main__': class Test(EventLoop): def handle(self): data = os.read(self.fileno, 100) - if data == 'q\n': - self.stop() - else: - os.write(1, 'Received message: %r\n' % data) - def handle_timer(self): - print time.strftime('%c') + os.write(1, 'Received message: %r\n' % data) + def handle_signal(self, signum): + os.write(1, 'Signal %d received, stopping\n' % signum) + self.stop() - p = Test(0, timer=5) + p = Test(0, signals={signal.SIGTERM: None, signal.SIGINT: None}) - os.write(1, 'Say a lot of things, then press write just "q" to stop: ') + os.write(1, 'Say a lot of things, then press Ctrl-C or kill me to stop: ') p.loop() os.write(1, 'Ok, bye!\n')