onoff/command.py

   1 import logging
   2
   3 from .common import OnoffDevice, ST_ACTIVE, ST_TRANSITION
   4 from .gobject import spawn_child
   5
   6 logger = logging.getLogger("onoff.command")
   7
   8 class OnoffCommand(OnoffDevice):
   9     def __init__(self, oncommand, offcommand):
  10         OnoffDevice.__init__(self)
  11         self.oncommand = oncommand
  12         self.offcommand = offcommand
  13         self.desired_state = 0 # bit mask of just ST_ACTIVE
  14         self.pid = None
  15         self.watch = None
  16         self.target_state = 0 # state the last command targeted
  17
  18     @property
  19     def state(self):
  20         if self.pid is not None:
  21             return self.desired_state | ST_TRANSITION
  22         return self.desired_state
  23
  24     def transition(self, state):
  25         command, name = [(self.offcommand, "offcommand"),
  26                          (self.oncommand, "oncommand")][state]
  27         self.target_state = state
  28         logger.info("invoking %s %s", name, " ".join(command))
  29         self.pid, self.watch = spawn_child(command, self.process_died)
  30         logger.debug("started %s as pid %d", name, self.pid)
  31         self.changestate(self.state)
  32
  33     def process_died(self, pid, condition):
  34         assert self.pid == pid
  35         assert self.watch is not None
  36         self.watch = None
  37         self.pid = None
  38         logger.info("command %d targeting %d completed", pid, self.target_state)
  39         if self.desired_state == self.target_state:
  40             self.changestate(self.state)
  41         else:
  42             logger.info("desired state changed to %d during invocation " +
  43                         "targeting %d", self.desired_state, self.target_state)
  44             self.transition(self.desired_state)
  45
  46     def activate(self):
  47         if self.desired_state != ST_ACTIVE:
  48             self.desired_state = ST_ACTIVE
  49             if self.pid is None:
  50                 self.transition(self.desired_state)
  51
  52     def deactivate(self):
  53         if self.desired_state != 0:
  54             self.desired_state = 0
  55             if self.pid is None:
  56                 self.transition(self.desired_state)