256 lines
7.6 KiB
Python
256 lines
7.6 KiB
Python
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#=======================================================================
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#
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# Python Lexical Analyser
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#
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# Classes for building NFAs and DFAs
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#
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#=======================================================================
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from __future__ import absolute_import
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import sys
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from .Transitions import TransitionMap
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try:
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from sys import maxsize as maxint
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except ImportError:
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from sys import maxint
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try:
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unichr
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except NameError:
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unichr = chr
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LOWEST_PRIORITY = -maxint
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class Machine(object):
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"""A collection of Nodes representing an NFA or DFA."""
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states = None # [Node]
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next_state_number = 1
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initial_states = None # {(name, bol): Node}
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def __init__(self):
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self.states = []
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self.initial_states = {}
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def __del__(self):
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#print "Destroying", self ###
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for state in self.states:
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state.destroy()
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def new_state(self):
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"""Add a new state to the machine and return it."""
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s = Node()
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n = self.next_state_number
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self.next_state_number = n + 1
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s.number = n
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self.states.append(s)
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return s
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def new_initial_state(self, name):
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state = self.new_state()
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self.make_initial_state(name, state)
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return state
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def make_initial_state(self, name, state):
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self.initial_states[name] = state
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def get_initial_state(self, name):
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return self.initial_states[name]
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def dump(self, file):
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file.write("Plex.Machine:\n")
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if self.initial_states is not None:
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file.write(" Initial states:\n")
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for (name, state) in sorted(self.initial_states.items()):
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file.write(" '%s': %d\n" % (name, state.number))
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for s in self.states:
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s.dump(file)
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class Node(object):
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"""A state of an NFA or DFA."""
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transitions = None # TransitionMap
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action = None # Action
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action_priority = None # integer
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number = 0 # for debug output
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epsilon_closure = None # used by nfa_to_dfa()
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def __init__(self):
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# Preinitialise the list of empty transitions, because
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# the nfa-to-dfa algorithm needs it
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#self.transitions = {'':[]}
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self.transitions = TransitionMap()
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self.action_priority = LOWEST_PRIORITY
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def destroy(self):
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#print "Destroying", self ###
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self.transitions = None
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self.action = None
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self.epsilon_closure = None
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def add_transition(self, event, new_state):
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self.transitions.add(event, new_state)
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def link_to(self, state):
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"""Add an epsilon-move from this state to another state."""
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self.add_transition('', state)
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def set_action(self, action, priority):
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"""Make this an accepting state with the given action. If
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there is already an action, choose the action with highest
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priority."""
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if priority > self.action_priority:
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self.action = action
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self.action_priority = priority
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def get_action(self):
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return self.action
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def get_action_priority(self):
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return self.action_priority
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def is_accepting(self):
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return self.action is not None
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def __str__(self):
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return "State %d" % self.number
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def dump(self, file):
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# Header
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file.write(" State %d:\n" % self.number)
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# Transitions
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# self.dump_transitions(file)
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self.transitions.dump(file)
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# Action
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action = self.action
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priority = self.action_priority
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if action is not None:
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file.write(" %s [priority %d]\n" % (action, priority))
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def __lt__(self, other):
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return self.number < other.number
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class FastMachine(object):
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"""
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FastMachine is a deterministic machine represented in a way that
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allows fast scanning.
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"""
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initial_states = None # {state_name:state}
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states = None # [state] where state = {event:state, 'else':state, 'action':Action}
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next_number = 1 # for debugging
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new_state_template = {
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'': None, 'bol': None, 'eol': None, 'eof': None, 'else': None
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}
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def __init__(self):
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self.initial_states = {}
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self.states = []
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def __del__(self):
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for state in self.states:
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state.clear()
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def new_state(self, action=None):
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number = self.next_number
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self.next_number = number + 1
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result = self.new_state_template.copy()
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result['number'] = number
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result['action'] = action
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self.states.append(result)
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return result
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def make_initial_state(self, name, state):
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self.initial_states[name] = state
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def add_transitions(self, state, event, new_state, maxint=maxint):
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if type(event) is tuple:
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code0, code1 = event
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if code0 == -maxint:
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state['else'] = new_state
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elif code1 != maxint:
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while code0 < code1:
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state[unichr(code0)] = new_state
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code0 += 1
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else:
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state[event] = new_state
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def get_initial_state(self, name):
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return self.initial_states[name]
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def dump(self, file):
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file.write("Plex.FastMachine:\n")
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file.write(" Initial states:\n")
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for name, state in sorted(self.initial_states.items()):
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file.write(" %s: %s\n" % (repr(name), state['number']))
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for state in self.states:
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self.dump_state(state, file)
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def dump_state(self, state, file):
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# Header
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file.write(" State %d:\n" % state['number'])
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# Transitions
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self.dump_transitions(state, file)
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# Action
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action = state['action']
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if action is not None:
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file.write(" %s\n" % action)
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def dump_transitions(self, state, file):
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chars_leading_to_state = {}
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special_to_state = {}
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for (c, s) in state.items():
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if len(c) == 1:
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chars = chars_leading_to_state.get(id(s), None)
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if chars is None:
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chars = []
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chars_leading_to_state[id(s)] = chars
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chars.append(c)
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elif len(c) <= 4:
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special_to_state[c] = s
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ranges_to_state = {}
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for state in self.states:
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char_list = chars_leading_to_state.get(id(state), None)
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if char_list:
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ranges = self.chars_to_ranges(char_list)
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ranges_to_state[ranges] = state
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ranges_list = ranges_to_state.keys()
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ranges_list.sort()
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for ranges in ranges_list:
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key = self.ranges_to_string(ranges)
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state = ranges_to_state[ranges]
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file.write(" %s --> State %d\n" % (key, state['number']))
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for key in ('bol', 'eol', 'eof', 'else'):
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state = special_to_state.get(key, None)
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if state:
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file.write(" %s --> State %d\n" % (key, state['number']))
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def chars_to_ranges(self, char_list):
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char_list.sort()
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i = 0
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n = len(char_list)
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result = []
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while i < n:
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c1 = ord(char_list[i])
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c2 = c1
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i += 1
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while i < n and ord(char_list[i]) == c2 + 1:
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i += 1
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c2 += 1
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result.append((chr(c1), chr(c2)))
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return tuple(result)
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def ranges_to_string(self, range_list):
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return ','.join(map(self.range_to_string, range_list))
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def range_to_string(self, range_tuple):
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(c1, c2) = range_tuple
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if c1 == c2:
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return repr(c1)
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else:
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return "%s..%s" % (repr(c1), repr(c2))
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