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#!/usr/bin/env python
# M Newville <newville@cars.uchicago.edu>
# The University of Chicago, 2010
# Epics Open License
"""
alarm module -- Alarm class
"""
import sys
import time
import operator
from . import pv
from .utils import is_string
class Alarm(object):
""" alarm class for a PV:
run a user-supplied callback when a PV's value goes out of range
quick synopsis:
The supplied callback will be run when a comparison of the PV's
value and a trip point is True. An optional alert delay can be
set to limit how frequently the callback is run
arguments:
pvname name of PV for which to set alarm
trip_point value of trip point
comparison a string for the comparison operation: one of
'eq', 'ne', 'le', 'lt', 'ge', 'gt'
'==', '!=', '<=', '<' , '>=', '>'
callback function to run when comparison(value,trip_point) is True
alert_delay time (in seconds) to stay quiet after executing a callback.
this is a minimum time, as it is checked only when a PVs
value actually changes. See note below.
example:
>>> from epics import alarm, poll
>>> def alarmHandler(pvname=None, value=None, **kw):
>>> print 'Alarm!! ', pvname, value
>>> alarm(pvname = 'XX.VAL',
>>> comparison='gt',
>>> callback = alarmHandler,
>>> trip_point=2.0,
>>> alert_delay=600)
>>> while True:
>>> poll()
when 'XX.VAL' exceeds (is 'gt') 2.0, the alarmHandler will be called.
notes:
alarm_delay: The alarm delay avoids over-notification by specifying a
time period to NOT send messages after a message has been
sent, even if a value is changing and out-of-range. Since
Epics callback are used to process events, the alarm state
will only be checked when a PV's value changes.
callback function: the user-supplied callback function should be prepared
for a large number of keyword arguments: use **kw!!!
For further explanation, see notes in pv.py.
These keyword arguments will always be included:
pvname name of PV
value current value of PV
char_value text string for PV
trip_point will hold the trip point used to define 'out of range'
comparison string
self.user_callback(pvname=pvname, value=value,
char_value=char_value,
trip_point=self.trip_point,
comparison=self.cmp.__name__, **kw)
"""
ops = {'eq': operator.__eq__,
'==': operator.__eq__,
'ne': operator.__ne__,
'!=': operator.__ne__,
'le': operator.__le__,
'<=': operator.__le__,
'lt': operator.__lt__,
'<' : operator.__lt__,
'ge': operator.__ge__,
'>=': operator.__ge__,
'gt': operator.__gt__,
'>' : operator.__gt__ }
def __init__(self, pvname, comparison=None, trip_point=None,
callback=None, alert_delay=10):
if isinstance(pvname, pv.PV):
self.pv = pvname
elif is_string(pvname):
self.pv = pv.get_pv(pvname)
self.pv.connect()
if self.pv is None or comparison is None or trip_point is None:
msg = 'alarm requires valid PV, comparison, and trip_point'
raise UserWarning(msg)
self.trip_point = trip_point
self.last_alert = 0
self.alert_delay = alert_delay
self.user_callback = callback
self.cmp = None
self.comp_name = 'Not Defined'
if callable(comparison):
self.comp_name = comparison.__name__
self.cmp = comparison
elif comparison is not None:
self.cmp = self.ops.get(comparison.replace('_', ''), None)
if self.cmp is not None:
self.comp_name = comparison
self.alarm_state = False
self.pv.add_callback(self.check_alarm)
self.check_alarm()
def __repr__(self):
return "<Alarm '%s', comp=%s, trip_point=%s >" % (self.pv.name,
self.comp_name,
self.trip_point)
def reset(self):
"resets the alarm state"
self.last_alert = 0
self.alarm_state = False
def check_alarm(self, pvname=None, value=None, char_value=None, **kw):
"""checks alarm status, act if needed.
"""
if (pvname is None or value is None or
self.cmp is None or self.trip_point is None): return
val = value
if char_value is None:
char_value = value
old_alarm_state = self.alarm_state
self.alarm_state = self.cmp(val, self.trip_point)
now = time.time()
if (self.alarm_state and not old_alarm_state and
((now - self.last_alert) > self.alert_delay)) :
self.last_alert = now
if callable(self.user_callback):
self.user_callback(pvname=pvname, value=value,
char_value=char_value,
trip_point=self.trip_point,
comparison=self.comp_name, **kw)
else:
sys.stdout.write('Alarm: %s=%s (%s)\n' % (pvname, char_value,
time.ctime()))
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