wickman · October 5, 2012 16:24 · Oct 5, 2012
diff --git a/clock.py b/clock.py
@@ -0,0 +1,71 @@
+from abc import ABCMeta, abstractmethod
+import threading
+
+
+class ClockInterface(object):
+  __metaclass__ = ABCMeta
+
+  @abstractmethod
+  def time(self):
+    pass
+
+  @abstractmethod
+  def tick(self, amount):
+    pass
+
+  @abstractmethod
+  def sleep(self, amount):
+    pass
+
+
+class Handshake(object):
+  def __init__(self):
+    self._syn_event = threading.Event()
+    self._ack_event = threading.Event()
+
+  def syn(self):
+    self._syn_event.wait()
+    self._ack_event.set()
+
+  def ack(self):
+    self._syn_event.set()
+    self._ack_event.wait()
+
+
+class ThreadedClock(ClockInterface):
+  def __init__(self):
+    self._time = 0
+    self._waiters = []  # queue of [stop time, Handshake]
+
+  def time(self):
+    return self._time
+
+  def _pop_waiter(self, end):
+    times_up = sorted((waiter for waiter in self._waiters if waiter[0] <= end),
+                       key=lambda element: element[0])
+    if times_up:
+      waiter = times_up[0]
+      self._waiters.remove(waiter)
+      return waiter
+
+  def tick(self, amount):
+    now = self._time
+    end = now + amount
+
+    while True:
+      waiter = self._pop_waiter(end)
+      if not waiter:
+        break
+
+      waiter_time, waiter_handshake = waiter
+      self._time = waiter_time
+      waiter_handshake.ack()
+
+    self._time = end
+
+  def sleep(self, amount):
+    waiter_end = self._time + amount
+    waiter_handshake = Handshake()
+
+    self._waiters.append((waiter_end, waiter_handshake))
+    waiter_handshake.syn()