Machines.py

#=======================================================================
#
#   Python Lexical Analyser
#
#   Classes for building NFAs and DFAs
#
#=======================================================================

import sys
from sys import maxint
from types import TupleType

from Transitions import TransitionMap

LOWEST_PRIORITY = -sys.maxint

class Machine(object):
  """A collection of Nodes representing an NFA or DFA."""
  states = None         # [Node]
  next_state_number = 1
  initial_states = None # {(name, bol): Node}

  def __init__(self):
    self.states = []
    self.initial_states = {}

  def __del__(self):
    #print "Destroying", self ###
    for state in self.states:
      state.destroy()

  def new_state(self):
    """Add a new state to the machine and return it."""
    s = Node()
    n = self.next_state_number
    self.next_state_number = n + 1
    s.number = n
    self.states.append(s)
    return s

  def new_initial_state(self, name):
    state = self.new_state()
    self.make_initial_state(name, state)
    return state

  def make_initial_state(self, name, state):
    self.initial_states[name] = state

  def get_initial_state(self, name):
    return self.initial_states[name]
  
  def dump(self, file):
    file.write("Plex.Machine:\n")
    if self.initial_states is not None:
      file.write("   Initial states:\n")
      for (name, state) in self.initial_states.iteritems():
        file.write("      '%s': %d\n" % (name, state.number))
    for s in self.states:
      s.dump(file)

class Node(object):
  """A state of an NFA or DFA."""
  transitions = None       # TransitionMap
  action = None            # Action
  action_priority = None   # integer
  number = 0               # for debug output
  epsilon_closure = None   # used by nfa_to_dfa()

  def __init__(self):
    # Preinitialise the list of empty transitions, because
    # the nfa-to-dfa algorithm needs it
    #self.transitions = {'':[]}
    self.transitions = TransitionMap()
    self.action_priority = LOWEST_PRIORITY

  def destroy(self):
    #print "Destroying", self ###
    self.transitions = None
    self.action = None
    self.epsilon_closure = None

  def add_transition(self, event, new_state):
    self.transitions.add(event, new_state)
  
  def link_to(self, state):
    """Add an epsilon-move from this state to another state."""
    self.add_transition('', state)

  def set_action(self, action, priority):
    """Make this an accepting state with the given action. If 
    there is already an action, choose the action with highest
    priority."""
    if priority > self.action_priority:
      self.action = action
      self.action_priority = priority

  def get_action(self):
    return self.action

  def get_action_priority(self):
    return self.action_priority

  def is_accepting(self):
    return self.action is not None

  def __str__(self):
    return "State %d" % self.number

  def dump(self, file):
    # Header
    file.write("   State %d:\n" % self.number)
    # Transitions
#        self.dump_transitions(file)
    self.transitions.dump(file)
    # Action
    action = self.action
    priority = self.action_priority
    if action is not None:
      file.write("      %s [priority %d]\n" % (action, priority))
  

class FastMachine(object):
  """
  FastMachine is a deterministic machine represented in a way that
  allows fast scanning.
  """
  initial_states = None # {state_name:state}
  states = None         # [state]
                        # where state = {event:state, 'else':state, 'action':Action}
  next_number = 1       # for debugging
  
  new_state_template = {
    '':None, 'bol':None, 'eol':None, 'eof':None, 'else':None
  }
  
  def __init__(self, old_machine = None):
    self.initial_states = initial_states = {}
    self.states = []
    if old_machine:
      self.old_to_new = old_to_new = {}
      for old_state in old_machine.states:
        new_state = self.new_state()
        old_to_new[old_state] = new_state
      for name, old_state in old_machine.initial_states.iteritems():
        initial_states[name] = old_to_new[old_state]
      for old_state in old_machine.states:
        new_state = old_to_new[old_state]
        for event, old_state_set in old_state.transitions.iteritems():
          if old_state_set:
            new_state[event] = old_to_new[old_state_set.keys()[0]]
          else:
            new_state[event] = None
        new_state['action'] = old_state.action
  
  def __del__(self):
    for state in self.states:
      state.clear()
  
  def new_state(self, action = None):
    number = self.next_number
    self.next_number = number + 1
    result = self.new_state_template.copy()
    result['number'] = number
    result['action'] = action
    self.states.append(result)
    return result
  
  def make_initial_state(self, name, state):
    self.initial_states[name] = state
  
  def add_transitions(self, state, event, new_state):
    if type(event) == TupleType:
      code0, code1 = event
      if code0 == -maxint:
        state['else'] = new_state
      elif code1 != maxint:
        while code0 < code1:
          state[chr(code0)] = new_state
          code0 = code0 + 1
    else:
      state[event] = new_state
  
  def get_initial_state(self, name):
    return self.initial_states[name]
  
  def dump(self, file):
    file.write("Plex.FastMachine:\n")
    file.write("   Initial states:\n")
    for name, state in self.initial_states.iteritems():
      file.write("      %s: %s\n" % (repr(name), state['number']))
    for state in self.states:
      self.dump_state(state, file)

  def dump_state(self, state, file):
    # Header
    file.write("   State %d:\n" % state['number'])
    # Transitions
    self.dump_transitions(state, file)
    # Action
    action = state['action']
    if action is not None:
      file.write("      %s\n" % action)
  
  def dump_transitions(self, state, file):
    chars_leading_to_state = {}
    special_to_state = {}
    for (c, s) in state.iteritems():
      if len(c) == 1:
        chars = chars_leading_to_state.get(id(s), None)
        if chars is None:
          chars = []
          chars_leading_to_state[id(s)] = chars
        chars.append(c)
      elif len(c) <= 4:
        special_to_state[c] = s
    ranges_to_state = {}
    for state in self.states:
      char_list = chars_leading_to_state.get(id(state), None)
      if char_list:
        ranges = self.chars_to_ranges(char_list)
        ranges_to_state[ranges] = state
    ranges_list = ranges_to_state.keys()
    ranges_list.sort()
    for ranges in ranges_list:
      key = self.ranges_to_string(ranges)
      state = ranges_to_state[ranges]
      file.write("      %s --> State %d\n" % (key, state['number']))
    for key in ('bol', 'eol', 'eof', 'else'):
      state = special_to_state.get(key, None)
      if state:
        file.write("      %s --> State %d\n" % (key, state['number']))

  def chars_to_ranges(self, char_list):
    char_list.sort()
    i = 0
    n = len(char_list)
    result = []
    while i < n:
      c1 = ord(char_list[i])
      c2 = c1
      i = i + 1
      while i < n and ord(char_list[i]) == c2 + 1:
        i = i + 1
        c2 = c2 + 1
      result.append((chr(c1), chr(c2)))
    return tuple(result)
  
  def ranges_to_string(self, range_list):
    return ','.join(map(self.range_to_string, range_list))
  
  def range_to_string(self, range_tuple):
    (c1, c2) = range_tuple
    if c1 == c2:
      return repr(c1)
    else:
      return "%s..%s" % (repr(c1), repr(c2))