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Diffstat (limited to 'python/gevent/_waiter.py')
| -rw-r--r-- | python/gevent/_waiter.py | 204 |
1 files changed, 0 insertions, 204 deletions
diff --git a/python/gevent/_waiter.py b/python/gevent/_waiter.py deleted file mode 100644 index b9ba3e8..0000000 --- a/python/gevent/_waiter.py +++ /dev/null @@ -1,204 +0,0 @@ -# -*- coding: utf-8 -*- -# copyright 2018 gevent -# cython: auto_pickle=False,embedsignature=True,always_allow_keywords=False -""" -Low-level waiting primitives. - -""" -from __future__ import absolute_import -from __future__ import division -from __future__ import print_function - -import sys - -from gevent._hub_local import get_hub_noargs as get_hub -from gevent.exceptions import ConcurrentObjectUseError - -__all__ = [ - 'Waiter', -] - -_NONE = object() - -locals()['getcurrent'] = __import__('greenlet').getcurrent -locals()['greenlet_init'] = lambda: None - - -class Waiter(object): - """ - A low level communication utility for greenlets. - - Waiter is a wrapper around greenlet's ``switch()`` and ``throw()`` calls that makes them somewhat safer: - - * switching will occur only if the waiting greenlet is executing :meth:`get` method currently; - * any error raised in the greenlet is handled inside :meth:`switch` and :meth:`throw` - * if :meth:`switch`/:meth:`throw` is called before the receiver calls :meth:`get`, then :class:`Waiter` - will store the value/exception. The following :meth:`get` will return the value/raise the exception. - - The :meth:`switch` and :meth:`throw` methods must only be called from the :class:`Hub` greenlet. - The :meth:`get` method must be called from a greenlet other than :class:`Hub`. - - >>> result = Waiter() - >>> timer = get_hub().loop.timer(0.1) - >>> timer.start(result.switch, 'hello from Waiter') - >>> result.get() # blocks for 0.1 seconds - 'hello from Waiter' - >>> timer.close() - - If switch is called before the greenlet gets a chance to call :meth:`get` then - :class:`Waiter` stores the value. - - >>> result = Waiter() - >>> timer = get_hub().loop.timer(0.1) - >>> timer.start(result.switch, 'hi from Waiter') - >>> sleep(0.2) - >>> result.get() # returns immediately without blocking - 'hi from Waiter' - >>> timer.close() - - .. warning:: - - This a limited and dangerous way to communicate between - greenlets. It can easily leave a greenlet unscheduled forever - if used incorrectly. Consider using safer classes such as - :class:`gevent.event.Event`, :class:`gevent.event.AsyncResult`, - or :class:`gevent.queue.Queue`. - """ - - __slots__ = ['hub', 'greenlet', 'value', '_exception'] - - def __init__(self, hub=None): - self.hub = get_hub() if hub is None else hub - self.greenlet = None - self.value = None - self._exception = _NONE - - def clear(self): - self.greenlet = None - self.value = None - self._exception = _NONE - - def __str__(self): - if self._exception is _NONE: - return '<%s greenlet=%s>' % (type(self).__name__, self.greenlet) - if self._exception is None: - return '<%s greenlet=%s value=%r>' % (type(self).__name__, self.greenlet, self.value) - return '<%s greenlet=%s exc_info=%r>' % (type(self).__name__, self.greenlet, self.exc_info) - - def ready(self): - """Return true if and only if it holds a value or an exception""" - return self._exception is not _NONE - - def successful(self): - """Return true if and only if it is ready and holds a value""" - return self._exception is None - - @property - def exc_info(self): - "Holds the exception info passed to :meth:`throw` if :meth:`throw` was called. Otherwise ``None``." - if self._exception is not _NONE: - return self._exception - - def switch(self, value): - """ - Switch to the greenlet if one's available. Otherwise store the - *value*. - - .. versionchanged:: 1.3b1 - The *value* is no longer optional. - """ - greenlet = self.greenlet - if greenlet is None: - self.value = value - self._exception = None - else: - if getcurrent() is not self.hub: # pylint:disable=undefined-variable - raise AssertionError("Can only use Waiter.switch method from the Hub greenlet") - switch = greenlet.switch - try: - switch(value) - except: # pylint:disable=bare-except - self.hub.handle_error(switch, *sys.exc_info()) - - def switch_args(self, *args): - return self.switch(args) - - def throw(self, *throw_args): - """Switch to the greenlet with the exception. If there's no greenlet, store the exception.""" - greenlet = self.greenlet - if greenlet is None: - self._exception = throw_args - else: - if getcurrent() is not self.hub: # pylint:disable=undefined-variable - raise AssertionError("Can only use Waiter.switch method from the Hub greenlet") - throw = greenlet.throw - try: - throw(*throw_args) - except: # pylint:disable=bare-except - self.hub.handle_error(throw, *sys.exc_info()) - - def get(self): - """If a value/an exception is stored, return/raise it. Otherwise until switch() or throw() is called.""" - if self._exception is not _NONE: - if self._exception is None: - return self.value - getcurrent().throw(*self._exception) # pylint:disable=undefined-variable - else: - if self.greenlet is not None: - raise ConcurrentObjectUseError('This Waiter is already used by %r' % (self.greenlet, )) - self.greenlet = getcurrent() # pylint:disable=undefined-variable - try: - return self.hub.switch() - finally: - self.greenlet = None - - def __call__(self, source): - if source.exception is None: - self.switch(source.value) - else: - self.throw(source.exception) - - # can also have a debugging version, that wraps the value in a tuple (self, value) in switch() - # and unwraps it in wait() thus checking that switch() was indeed called - - - -class MultipleWaiter(Waiter): - """ - An internal extension of Waiter that can be used if multiple objects - must be waited on, and there is a chance that in between waits greenlets - might be switched out. All greenlets that switch to this waiter - will have their value returned. - - This does not handle exceptions or throw methods. - """ - __slots__ = ['_values'] - - def __init__(self, hub=None): - Waiter.__init__(self, hub) - # we typically expect a relatively small number of these to be outstanding. - # since we pop from the left, a deque might be slightly - # more efficient, but since we're in the hub we avoid imports if - # we can help it to better support monkey-patching, and delaying the import - # here can be impractical (see https://github.com/gevent/gevent/issues/652) - self._values = list() - - def switch(self, value): - self._values.append(value) - Waiter.switch(self, True) - - def get(self): - if not self._values: - Waiter.get(self) - Waiter.clear(self) - - return self._values.pop(0) - -def _init(): - greenlet_init() # pylint:disable=undefined-variable - -_init() - - -from gevent._util import import_c_accel -import_c_accel(globals(), 'gevent.__waiter') |