Add support for an on_stop callback

echo_server.py

@@ -12,6 +12,7 @@ if __name__ == "__main__":
     pipe_io = EchoPipeIOServer('in', 'out')
     signal(SIGTERM, lambda a, b: pipe_io.stop())
     signal(SIGINT, lambda a, b: pipe_io.stop())
+    pipe_io.on_stop = lambda: print('Stopping...')
     pipe_io.start()
     print('Running pipe IO server with named pipes:')
     print(f'Input:  {pipe_io.in_pipe}')

pipe_io_server/pipe_io_server.py

@@ -1,5 +1,6 @@
 from abc import ABC, abstractmethod
 from threading import Thread, Event
+from typing import Callable
 
 from .pipe_reader_thread import PipeReaderThread
 from .pipe_writer_thread import PipeWriterThread
@@ -15,6 +16,7 @@ class PipeIOServer(ABC, Thread):
         self._stop_event = Event()
         self._reader_thread, self._writer_thread = self._create_io_threads()
         self._io_threads = (self._reader_thread, self._writer_thread)
+        self._on_stop = lambda: None
 
     def _create_pipes(self, permissions):
         Pipe(self.in_pipe).recreate(permissions)
@@ -58,6 +60,14 @@ class PipeIOServer(ABC, Thread):
                 thread.stop()
         Pipe(self.in_pipe).remove()
         Pipe(self.out_pipe).remove()
+        self._on_stop()
+
+    def _set_on_stop(self, value):
+        if not isinstance(value, Callable):
+            raise ValueError("Supplied object is not callable!")
+        self._on_stop = value
+
+    on_stop = property(fset=_set_on_stop)
 
     def wait(self):
         self._stop_event.wait()