terom@31: """
terom@31:     Syslog handling.
terom@31: """
terom@31: 
terom@43: import select
terom@43: 
terom@31: import logging; log = logging.getLogger('pvl.syslog.source')
terom@31: 
terom@31: class SyslogSource (object) :
terom@31:     """
terom@50:         Process syslog input from a given source.
terom@50:         
terom@50:         Implements an iterable mainloop doing continuous polling on the source, using either a timeout or
terom@50:         select():able source.
terom@31:     """
terom@31:     
terom@60:     def __init__ (self, source, parser, filter, poll=None) :
terom@31:         """
terom@31:             Using given underlying line source.
terom@50:                 
terom@50:                 source      - source to select() if poll=True
terom@50:                 poll        - polling behaviour
terom@31:         """
terom@50:         
terom@31:         self.source = source
terom@60:         self.parser = parser
terom@60:         self.filter = filter
terom@60: 
terom@43:         self._poll = poll
terom@31: 
terom@63:     def __iter__ (self) :
terom@60:         """
terom@60:             Yield available input.
terom@60:         """
terom@60: 
terom@60:         return self.filter(self.parser(self.source))
terom@60: 
terom@50:     def poll (self, poll=None) :
terom@31:         """
terom@50:             Poll our source for input, with given polling behaviour:
terom@50:                 True    - select() on source
terom@50:                 False   - peek on source
terom@50:                 float   - timeout in seconds
terom@43: 
terom@43:             Returns True if we have input waiting, False on timeout with no input. None on indeterminate.
terom@43:         """
terom@43: 
terom@50:         reading = writing = ()
terom@43:         
terom@50:         if poll is True :
terom@50:             timeout = None # block
terom@50:             reading += (self.source, ) # file-like object with fileno()
terom@43: 
terom@50:         elif not poll :
terom@50:             timeout = 0.0 # do not block
terom@50: 
terom@50:         else :
terom@50:             timeout = float(poll)
terom@43: 
terom@48:         log.debug("%s", timeout)
terom@43:     
terom@43:         # select
terom@50:         readable, writeable, ex = select.select(reading, writing, [], timeout)
terom@43: 
terom@50:         if readable :
terom@43:             return True
terom@43: 
terom@50:         elif reading :
terom@43:             # timeout
terom@43:             return False
terom@43: 
terom@50:         else :
terom@50:             # unknown
terom@50:             return None
terom@50: 
terom@50:     def main (self, poll=None) :
terom@43:         """
terom@50:             yield items from syslog source, polling as given.
terom@43: 
terom@43:             Returns once no more lines are available.
terom@43: 
terom@50:             XXX: reconnect? or source takes care of that..
terom@50:             TODO: SIGINT -> finish iteration and return?
terom@43:         """
terom@50: 
terom@50:         if poll is None :
terom@50:             poll = self._poll
terom@43:         
terom@43:         # mainloop
terom@43:         while True :
terom@43:             # pull in messages
terom@63:             for item in self :
terom@48:                 log.debug("%s", item)
terom@43:                 yield item
terom@31:             
terom@43:             # poll
terom@50:             if poll :
terom@43:                 # wait
terom@50:                 self.poll(poll)
terom@43:             else :
terom@43:                 # done
terom@43:                 break
terom@43: 
terom@43:         log.debug("exit")
terom@43: