/usr/lib/python2.7/dist-packages/eventlet/coros.py is in python-eventlet 0.20.0-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 | from __future__ import print_function
from eventlet import event as _event
class metaphore(object):
"""This is sort of an inverse semaphore: a counter that starts at 0 and
waits only if nonzero. It's used to implement a "wait for all" scenario.
>>> from eventlet import coros, spawn_n
>>> count = coros.metaphore()
>>> count.wait()
>>> def decrementer(count, id):
... print("{0} decrementing".format(id))
... count.dec()
...
>>> _ = spawn_n(decrementer, count, 'A')
>>> _ = spawn_n(decrementer, count, 'B')
>>> count.inc(2)
>>> count.wait()
A decrementing
B decrementing
"""
def __init__(self):
self.counter = 0
self.event = _event.Event()
# send() right away, else we'd wait on the default 0 count!
self.event.send()
def inc(self, by=1):
"""Increment our counter. If this transitions the counter from zero to
nonzero, make any subsequent :meth:`wait` call wait.
"""
assert by > 0
self.counter += by
if self.counter == by:
# If we just incremented self.counter by 'by', and the new count
# equals 'by', then the old value of self.counter was 0.
# Transitioning from 0 to a nonzero value means wait() must
# actually wait.
self.event.reset()
def dec(self, by=1):
"""Decrement our counter. If this transitions the counter from nonzero
to zero, a current or subsequent wait() call need no longer wait.
"""
assert by > 0
self.counter -= by
if self.counter <= 0:
# Don't leave self.counter < 0, that will screw things up in
# future calls.
self.counter = 0
# Transitioning from nonzero to 0 means wait() need no longer wait.
self.event.send()
def wait(self):
"""Suspend the caller only if our count is nonzero. In that case,
resume the caller once the count decrements to zero again.
"""
self.event.wait()
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