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# Copyright 1999-2009 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
from _emerge.AsynchronousTask import AsynchronousTask
from portage import os
class CompositeTask(AsynchronousTask):
__slots__ = ("scheduler",) + ("_current_task",)
def isAlive(self):
return self._current_task is not None
def cancel(self):
self.cancelled = True
if self._current_task is not None:
self._current_task.cancel()
def _poll(self):
"""
This does a loop calling self._current_task.poll()
repeatedly as long as the value of self._current_task
keeps changing. It calls poll() a maximum of one time
for a given self._current_task instance. This is useful
since calling poll() on a task can trigger advance to
the next task could eventually lead to the returncode
being set in cases when polling only a single task would
not have the same effect.
"""
prev = None
while True:
task = self._current_task
if task is None or task is prev:
# don't poll the same task more than once
break
task.poll()
prev = task
return self.returncode
def _wait(self):
prev = None
while True:
task = self._current_task
if task is None:
# don't wait for the same task more than once
break
if task is prev:
# Before the task.wait() method returned, an exit
# listener should have set self._current_task to either
# a different task or None. Something is wrong.
raise AssertionError("self._current_task has not " + \
"changed since calling wait", self, task)
task.wait()
prev = task
return self.returncode
def _assert_current(self, task):
"""
Raises an AssertionError if the given task is not the
same one as self._current_task. This can be useful
for detecting bugs.
"""
if task is not self._current_task:
raise AssertionError("Unrecognized task: %s" % (task,))
def _default_exit(self, task):
"""
Calls _assert_current() on the given task and then sets the
composite returncode attribute if task.returncode != os.EX_OK.
If the task failed then self._current_task will be set to None.
Subclasses can use this as a generic task exit callback.
@rtype: int
@returns: The task.returncode attribute.
"""
self._assert_current(task)
if task.returncode != os.EX_OK:
self.returncode = task.returncode
self._current_task = None
return task.returncode
def _final_exit(self, task):
"""
Assumes that task is the final task of this composite task.
Calls _default_exit() and sets self.returncode to the task's
returncode and sets self._current_task to None.
"""
self._default_exit(task)
self._current_task = None
self.returncode = task.returncode
return self.returncode
def _default_final_exit(self, task):
"""
This calls _final_exit() and then wait().
Subclasses can use this as a generic final task exit callback.
"""
self._final_exit(task)
return self.wait()
def _start_task(self, task, exit_handler):
"""
Register exit handler for the given task, set it
as self._current_task, and call task.start().
Subclasses can use this as a generic way to start
a task.
"""
task.addExitListener(exit_handler)
self._current_task = task
task.start()
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