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# Copyright 2016 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
#
# This module provides an extended subset of the asyncio.futures.Futures
# interface.
__all__ = (
"CancelledError",
"ExtendedFuture",
"InvalidStateError",
)
import concurrent.futures
from concurrent.futures import Future, CancelledError
try:
from concurrent.futures import InvalidStateError
except ImportError:
from portage.util.futures.futures import InvalidStateError
# Create our one time settable unset constant
UNSET_CONST = Future()
UNSET_CONST.set_result(object())
class ExtendedFuture(Future):
"""Extended Future class adding convienince get and set operations with
default result capabilities for unset result(). It also adds pass
capability for duplicate set_result() calls.
"""
def __init__(self, default_result=UNSET_CONST.result()):
"""Class init
@param default_result: Optional data type/value to return in the event
of a result() call when result has not yet been
set.
"""
self.default_result = default_result
super().__init__()
self.set = self.set_result
def set_result(self, data, ignore_InvalidState=False):
"""Set the Future's result to the data, optionally don't raise
an error for 'InvalidStateError' errors
@param ignore_exception: Boolean
"""
if ignore_InvalidState:
try:
super().set_result(data)
except InvalidStateError:
pass
else:
super().set_result(data)
def get(self, default=UNSET_CONST.result()):
"""Convenience function to wrap result() but adds an optional
default value to return rather than raise an InvalidStateError
@param default: Optional override for the classwide default_result
@returns: the result data or the default value, raisies an exception
if result is unset and no default is defined.
"""
if default is not UNSET_CONST.result():
pass
elif self.default_result is not UNSET_CONST.result():
default = self.default_result
if default is not UNSET_CONST.result():
try:
data = self.result()
except InvalidStateError:
data = default
else:
data = self.result()
return data
def exception(self):
try:
return super().exception(timeout=0)
except concurrent.futures.TimeoutError:
raise InvalidStateError
def result(self):
try:
return super().result(timeout=0)
except concurrent.futures.TimeoutError:
raise InvalidStateError
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