+# vim: set encoding=utf-8 et sw=4 sts=4 :
+
+r"""
+A simple event loop.
+
+Please see EventLoop class documentation for more info.
+"""
+
+from select import poll, POLLIN, POLLPRI, POLLERR
+
+__ALL__ = ('EventLoop')
+
+class EventLoop:
+ r"""EventLoop(file[, handler]) -> EventLoop instance
+
+ This class implements a simple event loop based on select module.
+ It "listens" to activity a single 'file' object (a file, a pipe,
+ a socket, or even a simple file descriptor) and calls a 'handler'
+ function (or the handle() method if you prefer subclassing) every
+ time the file is ready for reading (or has an error).
+
+ This is a really simple example of usage using a hanlder callable:
+
+ >>> import os
+ >>> def handle(event_loop):
+ data = os.read(event_loop.fileno, 100)
+ os.write(1, 'Received message: %r\n' % data)
+ >>> p = EventLoop(0, handle)
+ >>> p.loop(once=True)
+
+ In this example only one event is handled (see the 'once' argument
+ of loop).
+
+ A more complex example, making a subclass and explicitly stopping
+ the loop, looks something like this:
+
+ >>> 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)
+ >>> p = Test(0)
+ >>> p.loop()
+
+ This example loops until the user enters a single "q", when stop()
+ is called and the event loop is exited.
+ """
+
+ def __init__(self, file, handler=None):
+ r"""Initialize the EventLoop object.
+
+ See EventLoop class documentation for more info.
+ """
+ self.poll = poll()
+ self._stop = False
+ self.__register(file)
+ self.handler = handler
+
+ 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_file(self, file):
+ r"""set_file(file) -> None :: New file object to be monitored
+
+ Unregister the previous file object being monitored and register
+ a new one.
+ """
+ self.poll.unregister(self.fileno)
+ self.__register(file)
+
+ def get_file(self):
+ r"get_file() -> file object/int :: Get the current file object/fd."
+ return self._file
+
+ file = property(get_file, set_file, doc='File object (or descriptor)')
+
+ def get_fileno(self):
+ r"get_fileno() -> int :: Get the current file descriptor"
+ if hasattr(self.file, 'fileno'):
+ return self.file.fileno()
+ return self.file
+
+ fileno = property(get_fileno, doc='File descriptor (never a file object)')
+
+ def stop(self):
+ r"""stop() -> None :: Stop the event loop.
+
+ The event loop will be interrupted as soon as the current handler
+ finishes.
+ """
+ self._stop = True
+
+ def loop(self, once=False):
+ r"""loop([once]) -> None :: Wait for events.
+
+ Wait for events and handle then when they arrive. If once is True,
+ then only 1 event is processed and then this method returns.
+ """
+ while True:
+ res = self.poll.poll()
+ if self.handler is not None:
+ self.handler(self)
+ else:
+ self.handle()
+ if self._stop or once:
+ self._stop = False
+ break
+
+ def handle(self):
+ r"handle() -> None :: Abstract method to be overriden to handle events."
+ raise NotImplementedError
+
+if __name__ == '__main__':
+
+ import os
+
+ def handle(event_loop):
+ data = os.read(event_loop.fileno, 100)
+ os.write(1, 'Received message: %r\n' % data)
+
+ p = EventLoop(0, handle)
+
+ os.write(1, 'Say something once: ')
+ p.loop(once=True)
+ os.write(1, 'Great!\n')
+
+ 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)
+
+ p = Test(0)
+
+ os.write(1, 'Say a lot of things, then press write just "q" to stop: ')
+ p.loop()
+ os.write(1, 'Ok, bye!\n')
+
projects / software / pymin.git / commitdiff