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von raredesign | Dez 3, 2019 | Allgemein | 0 Kommentare
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| Current Path : /var/lib/python-support/python2.6/gevent/ |
| Current File : //var/lib/python-support/python2.6/gevent/coros.py |
"""Locking primitives"""
# Copyright (c) 2009-2010 Denis Bilenko. See LICENSE for details.
import sys
import traceback
from gevent.core import active_event
from gevent.hub import get_hub, getcurrent
from gevent.timeout import Timeout
__all__ = ['Semaphore', 'DummySemaphore', 'BoundedSemaphore', 'RLock']
class Semaphore(object):
"""A semaphore manages a counter representing the number of release() calls minus the number of acquire() calls,
plus an initial value. The acquire() method blocks if necessary until it can return without making the counter
negative.
If not given, value defaults to 1."""
def __init__(self, value=1):
if value < 0:
raise ValueError("semaphore initial value must be >= 0")
self._links = []
self.counter = value
self._notifier = None
def __str__(self):
params = (self.__class__.__name__, self.counter, len(self._links))
return '<%s counter=%s _links[%s]>' % params
def locked(self):
return self.counter <= 0
def release(self):
self.counter += 1
if self._links and self.counter > 0 and self._notifier is None:
self._notifier = active_event(self._notify_links, list(self._links))
def _notify_links(self, links):
try:
for link in links:
if self.counter <= 0:
return
if link in self._links:
try:
link(self)
except:
traceback.print_exc()
try:
sys.stderr.write('Failed to notify link %r of %r\n\n' % (link, self))
except:
traceback.print_exc()
finally:
self._notifier = None
def rawlink(self, callback):
"""Register a callback to call when a counter is more than zero.
*callback* will be called in the :class:`Hub <gevent.hub.Hub>`, so it must not use blocking gevent API.
*callback* will be passed one argument: this instance.
"""
if not callable(callback):
raise TypeError('Expected callable: %r' % (callback, ))
self._links.append(callback)
if self.counter > 0 and self._notifier is None:
self._notifier = active_event(self._notify_links, list(self._links))
def unlink(self, callback):
"""Remove the callback set by :meth:`rawlink`"""
try:
self._links.remove(callback)
except ValueError:
pass
def wait(self, timeout=None):
if self.counter > 0:
return self.counter
else:
switch = getcurrent().switch
self.rawlink(switch)
try:
timer = Timeout.start_new(timeout)
try:
try:
result = get_hub().switch()
assert result is self, 'Invalid switch into Semaphore.wait(): %r' % (result, )
except Timeout, ex:
if ex is not timer:
raise
finally:
timer.cancel()
finally:
self.unlink(switch)
return self.counter
def acquire(self, blocking=True, timeout=None):
if self.counter > 0:
self.counter -= 1
return True
elif not blocking:
return False
else:
switch = getcurrent().switch
self.rawlink(switch)
try:
timer = Timeout.start_new(timeout)
try:
try:
result = get_hub().switch()
assert result is self, 'Invalid switch into Semaphore.acquire(): %r' % (result, )
except Timeout, ex:
if ex is timer:
return False
raise
finally:
timer.cancel()
finally:
self.unlink(switch)
self.counter -= 1
assert self.counter >= 0
return True
def __enter__(self):
self.acquire()
def __exit__(self, typ, val, tb):
self.release()
class DummySemaphore(object):
"""A Semaphore initialized with "infinite" initial value. Neither of its methods ever block."""
def __str__(self):
return '<%s>' % self.__class__.__name__
def locked(self):
return False
def release(self):
pass
def rawlink(self, callback):
pass
def unlink(self, callback):
pass
def wait(self, timeout=None):
pass
def acquire(self, blocking=True, timeout=None):
pass
def __enter__(self):
self.acquire()
def __exit__(self, typ, val, tb):
self.release()
class BoundedSemaphore(Semaphore):
"""A bounded semaphore checks to make sure its current value doesn't exceed its initial value.
If it does, ``ValueError`` is raised. In most situations semaphores are used to guard resources
with limited capacity. If the semaphore is released too many times it's a sign of a bug.
If not given, *value* defaults to 1."""
def __init__(self, value=1):
Semaphore.__init__(self, value)
self._initial_value = value
def release(self):
if self.counter >= self._initial_value:
raise ValueError("Semaphore released too many times")
return Semaphore.release(self)
class RLock(object):
def __init__(self):
self._block = Semaphore(1)
self._owner = None
self._count = 0
def __repr__(self):
return "<%s(%s, %d)>" % (
self.__class__.__name__,
self._owner,
self._count)
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-aquired 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()
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