# gevent

# Source code for gevent.lock

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

    from gevent.hub import getcurrent
    from gevent._compat import PYPY
    from gevent._semaphore import Semaphore, BoundedSemaphore # pylint:disable=no-name-in-module,import-error

    __all__ = [
        'Semaphore',
        'DummySemaphore',
        'BoundedSemaphore',
        '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 _do_wait do we call back into Python and
    # allow switching threads). 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.)
    if PYPY:
        # TODO: Need to use monkey.get_original?
        try:
            from _thread import allocate_lock as _allocate_lock # pylint:disable=import-error,useless-suppression
            from _thread import get_ident as _get_ident # pylint:disable=import-error,useless-suppression
        except ImportError:
            # Python 2
            from thread import allocate_lock as _allocate_lock # pylint:disable=import-error,useless-suppression
            from thread import get_ident as _get_ident # pylint:disable=import-error,useless-suppression
        _sem_lock = _allocate_lock()

        def untraceable(f):
            # Don't allow re-entry to these functions in a single thread, as can
            # happen if a sys.settrace is used
            def wrapper(self):
                me = _get_ident()
                try:
                    count = self._locking[me]
                except KeyError:
                    count = self._locking[me] = 1
                else:
                    count = self._locking[me] = count + 1
                if count:
                    return

                try:
                    return f(self)
                finally:
                    count = count - 1
                    if not count:
                        del self._locking[me]
                    else:
                        self._locking[me] = count
            return wrapper

        class _OwnedLock(object):

            def __init__(self):
                self._owner = None
                self._block = _allocate_lock()
                self._locking = {}
                self._count = 0

            @untraceable
            def acquire(self):
                me = _get_ident()
                if self._owner == me:
                    self._count += 1
                    return

                self._owner = me
                self._block.acquire()
                self._count = 1

            @untraceable
            def release(self):
                self._count = count = self._count - 1
                if not count:
                    self._block.release()
                    self._owner = None

        # acquire, wait, and release all acquire the lock on entry and release it
        # on exit. acquire and wait can call _do_wait, which must release it on entry
        # and re-acquire it for them on exit.
        class _around(object):
            __slots__ = ('before', 'after')

            def __init__(self, before, after):
                self.before = before
                self.after = after

            def __enter__(self):
                self.before()

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

        def _decorate(func, cmname):
            # functools.wrap?
            def wrapped(self, *args, **kwargs):
                with getattr(self, cmname):
                    return func(self, *args, **kwargs)
            return wrapped

        Semaphore._py3k_acquire = Semaphore.acquire = _decorate(Semaphore.acquire, '_lock_locked')
        Semaphore.release = _decorate(Semaphore.release, '_lock_locked')
        Semaphore.wait = _decorate(Semaphore.wait, '_lock_locked')
        Semaphore._wait = _decorate(Semaphore._wait, '_lock_unlocked')

        _Sem_init = Semaphore.__init__

        def __init__(self, *args, **kwargs):
            l = self._lock_lock = _OwnedLock()
            self._lock_locked = _around(l.acquire, l.release)
            self._lock_unlocked = _around(l.release, l.acquire)

            _Sem_init(self, *args, **kwargs)

        Semaphore.__init__ = __init__

        del _decorate
        del untraceable

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

        A 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 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):
            """Waiting for a DummySemaphore returns immediately."""

        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.
        """

        def __init__(self):
            self._block = Semaphore(1)
            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=1):
            me = getcurrent()
            if self._owner is me:
                self._count = self._count + 1
                return 1
            rc = self._block.acquire(blocking)
            if rc:
                self._owner = me
                self._count = 1
            return rc

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

        def release(self):
            if self._owner is not getcurrent():
                raise RuntimeError("cannot release un-acquired lock")
            self._count = count = self._count - 1
            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()