# -*- test-case-name: twisted.python.test_threadable -*-
# Copyright (c) 2001-2010 Twisted Matrix Laboratories.
# See LICENSE for details.


"""
A module that will allow your program to be multi-threaded,
micro-threaded, and single-threaded.  Currently microthreads are
unimplemented.  The idea is to abstract away some commonly used
functionality so that I don't have to special-case it in all programs.
"""



from twisted.python import hook

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, *a, **b):
    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, *a, **b):
    self._threadable_lock.release()

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 threadmodule is not None:
        for klass in klasses:
            for methodName in klass.synchronized:
                hook.addPre(klass, methodName, _synchPre)
                hook.addPost(klass, methodName, _synchPost)

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 threadmodule 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 threadmodule is None:
        return _dummyID
    return threadmodule.get_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 thread as threadmodule
    import threading as threadingmodule
except ImportError:
    threadmodule = None
    threadingmodule = None
else:
    init(True)



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