def execATN(self, input: InputStream, ds0: DFAState):
if self.debug:
print("start state closure=" + str(ds0.configs))
if ds0.isAcceptState:
# allow zero-length tokens
self.captureSimState(self.prevAccept, input, ds0)
t = input.LA(1)
s = ds0 # s is current/from DFA state
while True: # while more work
if self.debug:
print("execATN loop starting closure: %s\n", s.configs)
# As we move src->trg, src->trg, we keep track of the previous trg to
# avoid looking up the DFA state again, which is expensive.
# If the previous target was already part of the DFA, we might
# be able to avoid doing a reach operation upon t. If s!=null,
# it means that semantic predicates didn't prevent us from
# creating a DFA state. Once we know s!=null, we check to see if
# the DFA state has an edge already for t. If so, we can just reuse
# it's configuration set; there's no point in re-computing it.
# This is kind of like doing DFA simulation within the ATN
# simulation because DFA simulation is really just a way to avoid
# computing reach/closure sets. Technically, once we know that
# we have a previously added DFA state, we could jump over to
# the DFA simulator. But, that would mean popping back and forth
# a lot and making things more complicated algorithmically.
# This optimization makes a lot of sense for loops within DFA.
# A character will take us back to an existing DFA state
# that already has lots of edges out of it. e.g., .* in comments.
# print("Target for:" + str(s) + " and:" + str(t))
target = self.getExistingTargetState(s, t)
# print("Existing:" + str(target))
if target is None:
target = self.computeTargetState(input, s, t)
# print("Computed:" + str(target))
if target == self.ERROR:
break
# If this is a consumable input element, make sure to consume before
# capturing the accept state so the input index, line, and char
# position accurately reflect the state of the interpreter at the
# end of the token.
if t != Token.EOF:
self.consume(input)
if target.isAcceptState:
self.captureSimState(self.prevAccept, input, target)
if t == Token.EOF:
break
t = input.LA(1)
s = target # flip; current DFA target becomes new src/from state
return self.failOrAccept(self.prevAccept, input, s.configs, t)
def testStream(self):
stream = InputStream("abcde")
self.assertEqual(0, stream.index)
self.assertEqual(5, stream.size)
self.assertEqual(ord("a"), stream.LA(1))
stream.consume()
self.assertEqual(1, stream.index)
stream.seek(5)
self.assertEqual(Token.EOF, stream.LA(1))
self.assertEqual("bcd", stream.getText(1, 3))
stream.reset()
self.assertEqual(0, stream.index)
def consume(self, input: InputStream):
curChar = input.LA(1)
if curChar == ord('\n'):
self.line += 1
self.column = 0
else:
self.column += 1
input.consume()
def accept(self, input: InputStream,
lexerActionExecutor: LexerActionExecutor, startIndex: int,
index: int, line: int, charPos: int):
if self.debug:
print("ACTION %s\n", lexerActionExecutor)
# seek to after last char in token
input.seek(index)
self.line = line
self.column = charPos
if input.LA(1) != Token.EOF:
self.consume(input)
if lexerActionExecutor is not None and self.recog is not None:
lexerActionExecutor.execute(self.recog, input, startIndex)
