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Diffstat (limited to 'pym/_emerge/TaskSequence.py')
-rw-r--r-- | pym/_emerge/TaskSequence.py | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/pym/_emerge/TaskSequence.py b/pym/_emerge/TaskSequence.py new file mode 100644 index 000000000..d0609f43e --- /dev/null +++ b/pym/_emerge/TaskSequence.py @@ -0,0 +1,40 @@ +from _emerge.CompositeTask import CompositeTask +from _emerge.AsynchronousTask import AsynchronousTask +import os +from collections import deque +class TaskSequence(CompositeTask): + """ + A collection of tasks that executes sequentially. Each task + must have a addExitListener() method that can be used as + a means to trigger movement from one task to the next. + """ + + __slots__ = ("_task_queue",) + + def __init__(self, **kwargs): + AsynchronousTask.__init__(self, **kwargs) + self._task_queue = deque() + + def add(self, task): + self._task_queue.append(task) + + def _start(self): + self._start_next_task() + + def cancel(self): + self._task_queue.clear() + CompositeTask.cancel(self) + + def _start_next_task(self): + self._start_task(self._task_queue.popleft(), + self._task_exit_handler) + + def _task_exit_handler(self, task): + if self._default_exit(task) != os.EX_OK: + self.wait() + elif self._task_queue: + self._start_next_task() + else: + self._final_exit(task) + self.wait() + |