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# Source code for gevent.lock

    # Copyright (c) 2009-2012 Denis Bilenko. See LICENSE for details.
    """
    Locking primitives.

    These include semaphores with arbitrary bounds (:class:`Semaphore` and
    its safer subclass :class:`BoundedSemaphore`) and a semaphore with
    infinite bounds (:class:`DummySemaphore`), along with a reentrant lock
    (:class:`RLock`) with the same API as :class:`threading.RLock`.
    """
    from __future__ import absolute_import
    from __future__ import print_function

    from gevent.hub import getcurrent
    from gevent._compat import PURE_PYTHON

    # This is the one exception to the rule of where to
    # import Semaphore, obviously
    from gevent import monkey
    from gevent._semaphore import Semaphore
    from gevent._semaphore import BoundedSemaphore

    __all__ = [
        'Semaphore',
        'BoundedSemaphore',
        'DummySemaphore',
        'RLock',
    ]

    # On PyPy, we don't compile the Semaphore class with Cython. Under
    # Cython, each individual method holds the GIL for its entire
    # duration, ensuring that no other thread can interrupt us in an
    # unsafe state (only when we _wait do we call back into Python and
    # allow switching threads; this is broken down into the
    # _drop_lock_for_switch_out and _acquire_lock_for_switch_in methods).
    # Simulate that here through the use of a manual lock. (We use a
    # separate lock for each semaphore to allow sys.settrace functions to
    # use locks *other* than the one being traced.) This, of course, must
    # also hold for PURE_PYTHON mode when no optional C extensions are
    # used.

    _allocate_lock, _get_ident = monkey.get_original(
        ('_thread', 'thread'),
        ('allocate_lock', 'get_ident')
    )

    def atomic(meth):
        def m(self, *args):
            with self._atomic:
                return meth(self, *args)
        return m

    class _GILLock(object):
        __slots__ = (
            '_owned_thread_id',
            '_gil',
            '_atomic',
            '_recursion_depth',
        )
        # Don't allow re-entry to these functions in a single thread, as
        # can happen if a sys.settrace is used. (XXX: What does that even
        # mean? Our original implementation that did that has been
        # replaced by something more robust)
        #
        # This is essentially a variant of the (pure-Python) RLock from the
        # standard library.
        def __init__(self):
            self._owned_thread_id = None
            self._gil = _allocate_lock()
            self._atomic = _allocate_lock()
            self._recursion_depth = 0

        @atomic
        def acquire(self):
            current_tid = _get_ident()
            if self._owned_thread_id == current_tid:
                self._recursion_depth += 1
                return True

            # Not owned by this thread. Only one thread will make it through this point.
            while 1:
                self._atomic.release()
                try:
                    self._gil.acquire()
                finally:
                    self._atomic.acquire()
                if self._owned_thread_id is None:
                    break

            self._owned_thread_id = current_tid
            self._recursion_depth = 1
            return True

        @atomic
        def release(self):
            current_tid = _get_ident()
            if current_tid != self._owned_thread_id:
                raise RuntimeError("%s: Releasing lock not owned by you. You: 0x%x; Owner: 0x%x" % (
                    self,
                    current_tid, self._owned_thread_id or 0,
                ))

            self._recursion_depth -= 1

            if not self._recursion_depth:
                self._owned_thread_id = None
                self._gil.release()

        def __enter__(self):
            self.acquire()

        def __exit__(self, t, v, tb):
            self.release()

        def locked(self):
            return self._gil.locked()

    class _AtomicSemaphoreMixin(object):
        # Behaves as though the GIL was held for the duration of acquire, wait,
        # and release, just as if we were in Cython.
        #
        # acquire, wait, and release all acquire the lock on entry and release it
        # on exit. acquire and wait can call _wait, which must release it on entry
        # and re-acquire it for them on exit.
        #
        # Note that this does *NOT*, in-and-of itself, make semaphores safe to use from multiple threads
        __slots__ = ()
        def __init__(self, *args, **kwargs):
            self._lock_lock = _GILLock() # pylint:disable=assigning-non-slot
            super(_AtomicSemaphoreMixin, self).__init__(*args, **kwargs)

        def _acquire_lock_for_switch_in(self):
            self._lock_lock.acquire()

        def _drop_lock_for_switch_out(self):
            self._lock_lock.release()

        def _notify_links(self, arrived_while_waiting):
            with self._lock_lock:
                return super(_AtomicSemaphoreMixin, self)._notify_links(arrived_while_waiting)

        def release(self):
            with self._lock_lock:
                return super(_AtomicSemaphoreMixin, self).release()

        def acquire(self, blocking=True, timeout=None):
            with self._lock_lock:
                return super(_AtomicSemaphoreMixin, self).acquire(blocking, timeout)

        _py3k_acquire = acquire

        def wait(self, timeout=None):
            with self._lock_lock:
                return super(_AtomicSemaphoreMixin, self).wait(timeout)

    class _AtomicSemaphore(_AtomicSemaphoreMixin, Semaphore):
        __doc__ = Semaphore.__doc__
        __slots__ = (
            '_lock_lock',
        )

    class _AtomicBoundedSemaphore(_AtomicSemaphoreMixin, BoundedSemaphore):
        __doc__ = BoundedSemaphore.__doc__
        __slots__ = (
            '_lock_lock',
        )

        def release(self): # pylint:disable=useless-super-delegation
            # This method is duplicated here so that it can get
            # properly documented.
            return super(_AtomicBoundedSemaphore, self).release()

    def _fixup_docstrings():
        for c in _AtomicSemaphore, _AtomicBoundedSemaphore:
            b = c.__mro__[2]
            assert b.__name__.endswith('Semaphore') and 'Atomic' not in b.__name__
            assert c.__doc__ == b.__doc__
            for m in 'acquire', 'release', 'wait':
                c_meth = getattr(c, m)
                b_meth = getattr(b, m)
                c_meth.__doc__ = b_meth.__doc__

    _fixup_docstrings()
    del _fixup_docstrings

    if PURE_PYTHON:
        Semaphore = _AtomicSemaphore
        Semaphore.__name__ = 'Semaphore'
        BoundedSemaphore = _AtomicBoundedSemaphore
        BoundedSemaphore.__name__ = 'BoundedSemaphore'

    class DummySemaphore(object):
        """
        DummySemaphore(value=None) -> DummySemaphore

        An object with the same API as :class:`Semaphore`,
        initialized with "infinite" initial value. None of its
        methods ever block.

        This can be used to parameterize on whether or not to actually
        guard access to a potentially limited resource. If the resource is
        actually limited, such as a fixed-size thread pool, use a real
        :class:`Semaphore`, but if the resource is unbounded, use an
        instance of this class. In that way none of the supporting code
        needs to change.

        Similarly, it can be used to parameterize on whether or not to
        enforce mutual exclusion to some underlying object. If the
        underlying object is known to be thread-safe itself mutual
        exclusion is not needed and a ``DummySemaphore`` can be used, but
        if that's not true, use a real ``Semaphore``.
        """

        # Internally this is used for exactly the purpose described in the
        # documentation. gevent.pool.Pool uses it instead of a Semaphore
        # when the pool size is unlimited, and
        # gevent.fileobject.FileObjectThread takes a parameter that
        # determines whether it should lock around IO to the underlying
        # file object.

        def __init__(self, value=None):
            """
            .. versionchanged:: 1.1rc3
                Accept and ignore a *value* argument for compatibility with Semaphore.
            """

        def __str__(self):
            return '<%s>' % self.__class__.__name__

        def locked(self):
            """A DummySemaphore is never locked so this always returns False."""
            return False

        def ready(self):
            """A DummySemaphore is never locked so this always returns True."""
            return True

        def release(self):
            """Releasing a dummy semaphore does nothing."""

        def rawlink(self, callback):
            # XXX should still work and notify?
            pass

        def unlink(self, callback):
            pass

        def wait(self, timeout=None): # pylint:disable=unused-argument
            """Waiting for a DummySemaphore returns immediately."""
            return 1

        def acquire(self, blocking=True, timeout=None):
            """
            A DummySemaphore can always be acquired immediately so this always
            returns True and ignores its arguments.

            .. versionchanged:: 1.1a1
               Always return *true*.
            """
            # pylint:disable=unused-argument
            return True

        def __enter__(self):
            pass

        def __exit__(self, typ, val, tb):
            pass

    class RLock(object):
        """
        A mutex that can be acquired more than once by the same greenlet.

        A mutex can only be locked by one greenlet at a time. A single greenlet
        can `acquire` the mutex as many times as desired, though. Each call to
        `acquire` must be paired with a matching call to `release`.

        It is an error for a greenlet that has not acquired the mutex
        to release it.

        Instances are context managers.
        """

        __slots__ = (
            '_block',
            '_owner',
            '_count',
            '__weakref__',
        )

        def __init__(self, hub=None):
            """
            .. versionchanged:: 20.5.1
               Add the ``hub`` argument.
            """
            self._block = Semaphore(1, hub)
            self._owner = None
            self._count = 0

        def __repr__(self):
            return "<%s at 0x%x _block=%s _count=%r _owner=%r)>" % (
                self.__class__.__name__,
                id(self),
                self._block,
                self._count,
                self._owner)

        def acquire(self, blocking=True, timeout=None):
            """
            Acquire the mutex, blocking if *blocking* is true, for up to
            *timeout* seconds.

            .. versionchanged:: 1.5a4
               Added the *timeout* parameter.

            :return: A boolean indicating whether the mutex was acquired.
            """
            me = getcurrent()
            if self._owner is me:
                self._count += 1
                return 1
            rc = self._block.acquire(blocking, timeout)
            if rc:
                self._owner = me
                self._count = 1
            return rc

        def __enter__(self):
            return self.acquire()

        def release(self):
            """
            Release the mutex.

            Only the greenlet that originally acquired the mutex can
            release it.
            """
            if self._owner is not getcurrent():
                raise RuntimeError("cannot release un-acquired lock. Owner: %r Current: %r" % (
                    self._owner, getcurrent()
                ))
            self._count = count = self._count - 1 # pylint:disable=consider-using-augmented-assign
            if not count:
                self._owner = None
                self._block.release()

        def __exit__(self, typ, value, tb):
            self.release()

        # Internal methods used by condition variables

        def _acquire_restore(self, count_owner):
            count, owner = count_owner
            self._block.acquire()
            self._count = count
            self._owner = owner

        def _release_save(self):
            count = self._count
            self._count = 0
            owner = self._owner
            self._owner = None
            self._block.release()
            return (count, owner)

        def _is_owned(self):
            return self._owner is getcurrent()