Initial Commit

lib/cherrypy/lib/locking.py

@@ -0,0 +1,47 @@
+import datetime
+
+
+class NeverExpires(object):
+    def expired(self):
+        return False
+
+
+class Timer(object):
+    """
+    A simple timer that will indicate when an expiration time has passed.
+    """
+    def __init__(self, expiration):
+        "Create a timer that expires at `expiration` (UTC datetime)"
+        self.expiration = expiration
+
+    @classmethod
+    def after(cls, elapsed):
+        """
+        Return a timer that will expire after `elapsed` passes.
+        """
+        return cls(datetime.datetime.utcnow() + elapsed)
+
+    def expired(self):
+        return datetime.datetime.utcnow() >= self.expiration
+
+
+class LockTimeout(Exception):
+    "An exception when a lock could not be acquired before a timeout period"
+
+
+class LockChecker(object):
+    """
+    Keep track of the time and detect if a timeout has expired
+    """
+    def __init__(self, session_id, timeout):
+        self.session_id = session_id
+        if timeout:
+            self.timer = Timer.after(timeout)
+        else:
+            self.timer = NeverExpires()
+
+    def expired(self):
+        if self.timer.expired():
+            raise LockTimeout(
+                "Timeout acquiring lock for %(session_id)s" % vars(self))
+        return False