Source code for pycopia.protocols

#!/usr/bin/python2
# -*- coding: utf-8 -*-
# vim:ts=4:sw=4:softtabstop=4:smarttab:expandtab
#
#    Copyright (C) 2010 Keith Dart <keith@dartworks.biz>
#
#    This library is free software; you can redistribute it and/or
#    modify it under the terms of the GNU Lesser General Public
#    License as published by the Free Software Foundation; either
#    version 2.1 of the License, or (at your option) any later version.
#
#    This library is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
#    Lesser General Public License for more details.

"""
Implment an abstraction of a protocol state machine.

"""
from __future__ import absolute_import
from __future__ import print_function
from __future__ import division


import sys
import re

from pycopia.stringmatch import compile_exact
from pycopia.aid import Enum


[docs]class ProtocolExit(Exception): """Raise when the protocol completes.""" pass
[docs]class ProtocolError(Exception): """Raise when the protocol transition is invalid.""" pass
RESET = Enum(0, "RESET") ANY = Enum(-1, "ANY") # default transition
[docs]def transition_error(text): raise ProtocolError('Symbol {!r} is undefined.'.format(text))
[docs]class StateMachine(object): ANY = ANY # place here for easy access from other modules RESET = RESET def __init__(self, initial_state=RESET): self._exact_transitions = {} self._any_transitions = {} self._re_transitions = {} self.default_transition = (transition_error, initial_state) self.initial_state = initial_state self.reset() def __str__(self): return "StateMachine: state=%r" % (self.current_state,)
[docs] def reset(self): self.current_state = self.initial_state self.stack = [] # primary stack self.altstack = [] # alternate stack # stacks for user
[docs] def push(self, v): self.stack.append(v)
[docs] def pop(self): return self.stack.pop()
[docs] def pushalt(self, v): self.altstack.append(v)
[docs] def popalt(self): return self.altstack.pop()
[docs] def step(self, symbol): state = self.current_state try: cre, action, next = self._exact_transitions[(symbol, state)] mo = cre.search(symbol) if mo: self.current_state = next if action: action(mo) return except KeyError: pass try: rel = self._re_transitions[state] for cre, action, next in rel: mo = cre.search(symbol) if mo: self.current_state = next if action: action(mo) return except KeyError: pass try: action, next = self._any_transitions[state] self.current_state = next if action: action(symbol) except KeyError: action, next = self.default_transition self.current_state = next if action: action(symbol) # transition constructors
[docs] def set_default_transition(self, action, next_state): self.default_transition = (action, next_state)
[docs] def add_exact(self, symbol, state, action, next_state): cre = compile_exact(symbol) self._exact_transitions[(symbol, state)] = (cre, action, next_state) # general add method that knows what you want. ;-)
[docs] def add(self, symbol, state, action, next_state): if symbol is ANY: self._any_transitions[state] = (action, next_state) elif is_exact(symbol): self.add_exact(symbol, state, action, next_state) else: self.add_regex(symbol, state, action, next_state)
[docs] def add_any(self, state, action, next_state): self._any_transitions[state] = (action, next_state)
[docs] def add_glob(self, expression, state, action, next_state): self.add_regex(glob_translate(expression), state, action, next_state)
[docs] def add_regex(self, expression, state, action, next_state, ignore_case=False, multiline=False): cre = re.compile(expression, _get_re_flags(ignore_case, multiline)) try: rel = self._re_transitions[state] rel.append((cre, action, next_state)) except KeyError: self._re_transitions[state] = [(cre, action, next_state)]
[docs] def add_list(self, expression_list, state, action, next_state): for input_symbol in expression_list: self.add_exact(input_symbol, state, action, next_state)
[docs]def is_exact(pattern): for c in pattern: if c in ".^$*?+\\{}(),[]|": return False return True
[docs]class Protocol(object): """Implement the actions for the state machine. Add bound methods to it.""" EOL = "\n" def __init__(self, eol=None): self.states = StateMachine() self.iostream = None self.data = None # extra data action handlers might use. self.eol = eol or self.EOL self.initialize(self.states) def __str__(self): if self.iostream is None: return "Protocol: fsm: {}. current: {}, Not running.".format( self.states, self.states.current_state) else: return "Protocol: fsm: {},\n current: {},\n iostream: {}".format( self.states, self.states.current_state, self.iostream)
[docs] def log(self, *args): print(*args, file=sys.stderr)
[docs] def run(self, iostream, data=None): self.iostream = iostream self.data = data states = self.states states.reset() self.start() try: while 1: nextline = iostream.readline() if nextline: states.step(nextline) else: break finally: self.iostream = None self.data = None
[docs] def step(self, iostream, data=None): self.iostream = iostream self.data = data try: nextline = iostream.readline() if nextline: self.states.step(nextline) else: raise ProtocolExit("No more data") finally: self.iostream = None self.data = None
[docs] def close(self): self.states = None self.iostream = None
[docs] def initialize(self, states): """Fill this in with state transitions.""" raise NotImplementedError
[docs] def start(self): return NotImplemented
[docs] def reset(self): self.states.reset()
[docs] def writeln(self, data): self.iostream.write(data + self.eol)
def _get_re_flags(ignore_case, multiline): flags = 0 if ignore_case: flags |= re.I if multiline: flags |= re.M return flags if __name__ == "__main__": from pycopia import autodebug from pycopia import IO class TestProtocol(Protocol): def initialize(self, fsm): fsm.set_default_transition(self._error, fsm.RESET) fsm.add("GREETINGS\n", fsm.RESET, self._bye, 2) fsm.add(fsm.ANY, 2, self._bye, fsm.RESET) def start(self): self.writeln("HELLO type GREETINGS") def _bye(self, match): self.writeln("BYE") raise ProtocolExit def _error(self, symbol): self.writeln("ERROR") proto = TestProtocol() try: proto.run(IO.ConsoleIO()) except ProtocolExit: print("exited")