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# -*- coding: utf-8 -*-
"""
Timeout encapsulation, complete with countdowns and scope managers.
"""
from __future__ import division
import time
import pwnlib
class _DummyContextClass(object):
def __enter__(self): pass
def __exit__(self,*a): pass
_DummyContext = _DummyContextClass()
class _countdown_handler(object):
def __init__(self, obj, timeout):
self.obj = obj
self.timeout = timeout
def __enter__(self):
self.old_timeout = self.obj._timeout
self.old_stop = self.obj._stop
self.obj._stop = time.time() + self.timeout
if self.old_stop:
self.obj._stop = min(self.obj._stop, self.old_stop)
self.obj._timeout = self.timeout
self.obj.timeout_change()
def __exit__(self, *a):
self.obj._timeout = self.old_timeout
self.obj._stop = self.old_stop
self.obj.timeout_change()
class _local_handler(object):
def __init__(self, obj, timeout):
self.obj = obj
self.timeout = timeout
def __enter__(self):
self.old_timeout = self.obj._timeout
self.old_stop = self.obj._stop
self.obj._stop = 0
self.obj._timeout = self.timeout # leverage validation
self.obj.timeout_change()
def __exit__(self, *a):
self.obj._timeout = self.old_timeout
self.obj._stop = self.old_stop
self.obj.timeout_change()
class TimeoutDefault(object):
def __repr__(self): return "pwnlib.timeout.Timeout.default"
def __str__(self): return "<default timeout>"
class Maximum(float):
def __repr__(self):
return 'pwnlib.timeout.maximum'
maximum = Maximum(2**20)
class Timeout(object):
"""
Implements a basic class which has a timeout, and support for
scoped timeout countdowns.
Valid timeout values are:
- ``Timeout.default`` use the global default value (``context.default``)
- ``Timeout.forever`` or :const:`None` never time out
- Any positive float, indicates timeouts in seconds
Example:
>>> context.timeout = 30
>>> t = Timeout()
>>> t.timeout == 30
True
>>> t = Timeout(5)
>>> t.timeout == 5
True
>>> i = 0
>>> with t.countdown():
... print(4 <= t.timeout and t.timeout <= 5)
...
True
>>> with t.countdown(0.5): # doctest: +ELLIPSIS
... while t.timeout:
... print(round(t.timeout,1))
... time.sleep(0.1)
0.5
0.4
0.3
0.2
0.1
>>> print(t.timeout)
5.0
>>> with t.local(0.5):# doctest: +ELLIPSIS
... for i in range(5):
... print(round(t.timeout,1))
... time.sleep(0.1)
0.5
0.5
0.5
0.5
...
>>> print(t.timeout)
5.0
"""
#: Value indicating that the timeout should not be changed
default = TimeoutDefault()
#: Value indicating that a timeout should not ever occur
forever = None
#: Maximum value for a timeout. Used to get around platform issues
#: with very large timeouts.
#:
#: OSX does not permit setting socket timeouts to 2**22.
#: Assume that if we receive a timeout of 2**21 or greater,
#: that the value is effectively infinite.
maximum = maximum
def __init__(self, timeout=default):
self._stop = 0
self.timeout = self._get_timeout_seconds(timeout)
@property
def timeout(self):
"""
Timeout for obj operations. By default, uses ``context.timeout``.
"""
timeout = self._timeout
stop = self._stop
if not stop:
return timeout
return max(stop-time.time(), 0)
@timeout.setter
def timeout(self, value):
assert not self._stop
self._timeout = self._get_timeout_seconds(value)
self.timeout_change()
def _get_timeout_seconds(self, value):
if value is self.default:
value = pwnlib.context.context.timeout
elif value is self.forever:
value = self.maximum
else:
value = float(value)
if value < 0:
raise AttributeError("timeout: Timeout cannot be negative")
if value > self.maximum:
value = self.maximum
return value
def countdown_active(self):
return (self._stop == 0) or (self._stop > time.time())
def timeout_change(self):
"""
Callback for subclasses to hook a timeout change.
"""
pass
def countdown(self, timeout = default):
"""
Scoped timeout setter. Sets the timeout within the scope,
and restores it when leaving the scope.
When accessing :attr:`timeout` within the scope, it will be
calculated against the time when the scope was entered, in a
countdown fashion.
If :const:`None` is specified for ``timeout``, then the current
timeout is used is made. This allows :const:`None` to be specified
as a default argument with less complexity.
"""
# Don't count down from infinity
if timeout is self.maximum:
return _DummyContext
if timeout is self.default and self.timeout is self.maximum:
return _DummyContext
if timeout is self.default:
timeout = self._timeout
return _countdown_handler(self, timeout)
def local(self, timeout):
"""
Scoped timeout setter. Sets the timeout within the scope,
and restores it when leaving the scope.
"""
if timeout is self.default or timeout == self.timeout:
return _DummyContext
return _local_handler(self, timeout)
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