Windows: Use 32-bit distribution of python

python/gevent/_waiter.py

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+# -*- 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')