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authorLance Stout <lancestout@gmail.com>2010-07-26 19:44:42 -0400
committerLance Stout <lancestout@gmail.com>2010-07-26 19:44:42 -0400
commitec860bf9e29f4a88fc1797faa1dbcf0c0fc3889c (patch)
tree28447ff0d4d248a9797bbf3ebe647e2adbf9d29a /sleekxmpp/xmlstream/statemanager.py
parent73a3d07ad9b9154e6f712012bad489207c9f8e85 (diff)
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Add StateManager as replacement for StateMachine.
Diffstat (limited to 'sleekxmpp/xmlstream/statemanager.py')
-rw-r--r--sleekxmpp/xmlstream/statemanager.py139
1 files changed, 139 insertions, 0 deletions
diff --git a/sleekxmpp/xmlstream/statemanager.py b/sleekxmpp/xmlstream/statemanager.py
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+"""
+ SleekXMPP: The Sleek XMPP Library
+ Copyright (C) 2010 Nathanael C. Fritz, Lance J.T. Stout
+ This file is part of SleekXMPP.
+
+ See the file LICENSE for copying permission.
+"""
+
+from __future__ import with_statement
+import threading
+
+
+class StateError(Exception):
+ """Raised whenever a state transition was attempted but failed."""
+
+
+class StateManager(object):
+ """
+ At the very core of SleekXMPP there is a need to track various
+ library configuration settings, XML stream features, and the
+ network connection status. The state manager is responsible for
+ tracking this information in a thread-safe manner.
+
+ State 'variables' store the current state of these items as simple
+ string values or booleans. Changing those values must be done
+ according to transitions defined when creating the state variable.
+
+ If a state variable is given a value that is not allowed according
+ to the transition definitions, a StateError is raised. When a
+ valid value is assigned an event is raised named:
+
+ _state_changed_nameofthestatevariable
+
+ The event carries a dictionary containing the previous and the new
+ state values.
+ """
+
+ def __init__(self, event_func=None):
+ """
+ Initialize the state manager. The parameter event_func should be
+ the event() method of a SleekXMPP object in order to enable
+ _state_changed_* events.
+ """
+ self.main_lock = threading.Lock()
+ self.locks = {}
+ self.state_variables = {}
+
+ if event_func is not None:
+ self.event = event_func
+ else:
+ self.event = lambda name, data: None
+
+ def add(self, name, default=False, values=None, transitions=None):
+ """
+ Create a new state variable.
+
+ When transitions is specified, only those defined state change
+ transitions will be allowed.
+
+ When values is specified (and not transitions), any state changes
+ between those values are allowed.
+
+ If neither values nor transitions are defined, then the state variable
+ will be a binary switch between True and False.
+ """
+ if name in self.state_variables:
+ raise IndexError("State variable %s already exists" % name)
+
+ self.locks[name] = threading.Lock()
+ with self.locks[name]:
+ var = {'value': default,
+ 'default': default,
+ 'transitions': {}}
+
+ if transitions is not None:
+ for start in transitions:
+ var['transitions'][start] = set(transitions[start])
+ elif values is not None:
+ values = set(values)
+ for value in values:
+ var['transitions'][value] = values
+ elif values is None:
+ var['transitions'] = {True: [False],
+ False: [True]}
+
+ self.state_variables[name] = var
+
+ def addStates(self, var_defs):
+ """
+ Create multiple state variables at once.
+ """
+ for var, data in var_defs:
+ self.add(var,
+ default=data.get('default', False),
+ values=data.get('values', None),
+ transitions=data.get('transitions', None))
+
+ def force_set(self, name, val):
+ """
+ Force setting a state variable's value by overriding transition checks.
+ """
+ with self.locks[name]:
+ self.state_variables[name]['value'] = val
+
+ def reset(self, name):
+ """
+ Reset a state variable to its default value.
+ """
+ with self.locks[name]:
+ default = self.state_variables[name]['default']
+ self.state_variables[name]['value'] = default
+
+ def __getitem__(self, name):
+ """
+ Get the value of a state variable if it exists.
+ """
+ with self.locks[name]:
+ if name not in self.state_variables:
+ raise IndexError("State variable %s does not exist" % name)
+ return self.state_variables[name]['value']
+
+ def __setitem__(self, name, val):
+ """
+ Attempt to set the value of a state variable, but raise StateError
+ if the transition is undefined.
+
+ A _state_changed_* event is triggered after a successful transition.
+ """
+ with self.locks[name]:
+ if name not in self.state_variables:
+ raise IndexError("State variable %s does not exist" % name)
+ current = self.state_variables[name]['value']
+ if current == val:
+ return
+ if val in self.state_variables[name]['transitions'][current]:
+ self.state_variables[name]['value'] = val
+ self.event('_state_changed_%s' % name, {'from': current, 'to': val})
+ else:
+ raise StateError("Can not transition from '%s' to '%s'" % (str(current), str(val)))