# -*- test-case-name: twisted.python.test_threadable -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
A module to provide some very basic threading primitives, such as
synchronization.
"""

from __future__ import division, absolute_import

from functools import wraps

class DummyLock(object):
"""
Hack to allow locks to be unpickled on an unthreaded system.
"""

def __reduce__(self):
return (unpickle_lock, ())



def unpickle_lock():
if threadingmodule is not None:
return XLock()
else:
return DummyLock()
unpickle_lock.__safe_for_unpickling__ = True



def _synchPre(self):
if '_threadable_lock' not in self.__dict__:
_synchLockCreator.acquire()
if '_threadable_lock' not in self.__dict__:
self.__dict__['_threadable_lock'] = XLock()
_synchLockCreator.release()
self._threadable_lock.acquire()



def _synchPost(self):
self._threadable_lock.release()



def _sync(klass, function):
@wraps(function)
def sync(self, *args, **kwargs):
_synchPre(self)
try:
return function(self, *args, **kwargs)
finally:
_synchPost(self)
return sync



def synchronize(*klasses):
"""
Make all methods listed in each class' synchronized attribute synchronized.

The synchronized attribute should be a list of strings, consisting of the
names of methods that must be synchronized. If we are running in threaded
mode these methods will be wrapped with a lock.
"""
if threadingmodule is not None:
for klass in klasses:
for methodName in klass.synchronized:
sync = _sync(klass, klass.__dict__[methodName])
setattr(klass, methodName, sync)



def init(with_threads=1):
"""Initialize threading.

Don't bother calling this. If it needs to happen, it will happen.
"""
global threaded, _synchLockCreator, XLock

if with_threads:
if not threaded:
if threadingmodule is not None:
threaded = True

class XLock(threadingmodule._RLock, object):
def __reduce__(self):
return (unpickle_lock, ())

_synchLockCreator = XLock()
else:
raise RuntimeError("Cannot initialize threading, platform lacks thread support")
else:
if threaded:
raise RuntimeError("Cannot uninitialize threads")
else:
pass



_dummyID = object()
def getThreadID():
if threadingmodule is None:
return _dummyID
return threadingmodule.currentThread().ident



def isInIOThread():
"""Are we in the thread responsable for I/O requests (the event loop)?
"""
return ioThread == getThreadID()



def registerAsIOThread():
"""Mark the current thread as responsable for I/O requests.
"""
global ioThread
ioThread = getThreadID()


ioThread = None
threaded = False



try:
import threading as threadingmodule
except ImportError:
threadingmodule = None
else:
init(True)



__all__ = ['isInIOThread', 'registerAsIOThread', 'getThreadID', 'XLock']