terom@2: """
terom@2:     Syslog handling.
terom@2: 
terom@2:     XXX: this belongs in pvl.syslog.source (apart from __iter__?)
terom@2: """
terom@2: 
terom@2: import select
terom@2: 
terom@2: import logging; log = logging.getLogger('pvl.syslog.source')
terom@2: 
terom@2: class SyslogSource (object) :
terom@2:     """
terom@2:         Process syslog input from a given source.
terom@2:         
terom@2:         Implements an iterable mainloop doing continuous polling on the source, using either a timeout or
terom@2:         select():able source.
terom@2:     """
terom@2:     
terom@2:     def __init__ (self, source, parser, filter, poll=None) :
terom@2:         """
terom@2:             Using given underlying line source.
terom@2:                 
terom@2:                 source      - source to select() if poll=True
terom@2:                 poll        - polling behaviour for source
terom@2:         """
terom@2:         
terom@2:         self.source = source
terom@2:         self.parser = parser
terom@2:         self.filter = filter
terom@2: 
terom@2:         self.poll = poll
terom@2: 
terom@2:     def __iter__ (self) :
terom@2:         """
terom@2:             Yield available input.
terom@2: 
terom@2:             Raises EOFError if source has been closed.
terom@2:         """
terom@2: 
terom@2:         return self.filter(self.parser(self.source))
terom@2:         
terom@2:     def fileno (self) :
terom@2:         return self.source.fileno()
terom@2: 
terom@2:     def select (self, poll=None, reading=(), writing=()) :
terom@2:         """
terom@2:             Poll our source for input, with given polling behaviour:
terom@2:                 True    - select() on source
terom@2:                 False   - peek on source
terom@2:                 float   - timeout in seconds
terom@2:             
terom@2:             Returns None on unknown, empty sequence on timeout, list of readables on select.
terom@2:         """
terom@2:         
terom@2:         if poll is True :
terom@2:             timeout = None # block
terom@2:             reading += (self, ) # source.fileno()
terom@2: 
terom@2:         elif not poll :
terom@2:             timeout = 0.0 # do not block
terom@2: 
terom@2:         else :
terom@2:             timeout = float(poll)
terom@2: 
terom@2:         log.debug("%s (%s)", reading, timeout)
terom@2:     
terom@2:         # select
terom@2:         readable, writeable, ex = select.select(reading, writing, [], timeout)
terom@2:         
terom@2:         log.debug("select: %s", readable)
terom@2: 
terom@2:         if readable :
terom@2:             return readable
terom@2: 
terom@2:         elif reading :
terom@2:             # timeout
terom@2:             # XXX: this is the same as readable
terom@2:             return ()
terom@2: 
terom@2:         else :
terom@2:             # unknown
terom@2:             return None
terom@2: 
terom@2:     def main (self, poll=None) :
terom@2:         """
terom@2:             Yield active syslog sources, polling as given.
terom@2: 
terom@2:             Returns once no more lines are available.
terom@2: 
terom@2:             XXX: reconnect? or source takes care of that..
terom@2:             TODO: SIGINT -> finish iteration and return?
terom@2:         """
terom@2: 
terom@2:         # from __init__
terom@2:         # note that we must interpret poll here, since False -> never poll
terom@2:         if poll is None :
terom@2:             poll = self.poll
terom@2: 
terom@2:         # mainloop
terom@2:         while True :
terom@2:             # caller is responsible for reading them!
terom@2:             yield self
terom@2:             
terom@2:             # poll
terom@2:             if poll :
terom@2:                 # wait
terom@2:                 self.select(poll)
terom@2: 
terom@2:             else :
terom@2:                 # done
terom@2:                 break
terom@2: 
terom@2:         log.debug("exit")
terom@2: 
terom@2:     def close (self) :
terom@2:         """
terom@2:             Close the syslog source, if possible.
terom@2: 
terom@2:         """
terom@2: 
terom@2:         # XXX: do all sources support close?
terom@2:         self.source.close()
terom@2: 
terom@2:     def __str__ (self) :
terom@2:         return ' | '.join((str(self.source), str(self.parser), str(self.filter)))
terom@2: