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1# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
2# Licensed to PSF under a Contributor Agreement.
3
4import os
5from typing import (
6 IO,
7 Any,
8 Dict,
9 Iterator,
10 List,
11 NoReturn,
12 Optional,
13 Sequence,
14 Tuple,
15 Union,
16)
17
18from blib2to3.pgen2 import grammar, token, tokenize
19from blib2to3.pgen2.tokenize import GoodTokenInfo
20
21Path = Union[str, "os.PathLike[str]"]
22
23
24class PgenGrammar(grammar.Grammar):
25 pass
26
27
28class ParserGenerator:
29 filename: Path
30 stream: IO[str]
31 generator: Iterator[GoodTokenInfo]
32 first: Dict[str, Optional[Dict[str, int]]]
33
34 def __init__(self, filename: Path, stream: Optional[IO[str]] = None) -> None:
35 close_stream = None
36 if stream is None:
37 stream = open(filename, encoding="utf-8")
38 close_stream = stream.close
39 self.filename = filename
40 self.stream = stream
41 self.generator = tokenize.generate_tokens(stream.readline)
42 self.gettoken() # Initialize lookahead
43 self.dfas, self.startsymbol = self.parse()
44 if close_stream is not None:
45 close_stream()
46 self.first = {} # map from symbol name to set of tokens
47 self.addfirstsets()
48
49 def make_grammar(self) -> PgenGrammar:
50 c = PgenGrammar()
51 names = list(self.dfas.keys())
52 names.sort()
53 names.remove(self.startsymbol)
54 names.insert(0, self.startsymbol)
55 for name in names:
56 i = 256 + len(c.symbol2number)
57 c.symbol2number[name] = i
58 c.number2symbol[i] = name
59 for name in names:
60 dfa = self.dfas[name]
61 states = []
62 for state in dfa:
63 arcs = []
64 for label, next in sorted(state.arcs.items()):
65 arcs.append((self.make_label(c, label), dfa.index(next)))
66 if state.isfinal:
67 arcs.append((0, dfa.index(state)))
68 states.append(arcs)
69 c.states.append(states)
70 c.dfas[c.symbol2number[name]] = (states, self.make_first(c, name))
71 c.start = c.symbol2number[self.startsymbol]
72 return c
73
74 def make_first(self, c: PgenGrammar, name: str) -> Dict[int, int]:
75 rawfirst = self.first[name]
76 assert rawfirst is not None
77 first = {}
78 for label in sorted(rawfirst):
79 ilabel = self.make_label(c, label)
80 ##assert ilabel not in first # XXX failed on <> ... !=
81 first[ilabel] = 1
82 return first
83
84 def make_label(self, c: PgenGrammar, label: str) -> int:
85 # XXX Maybe this should be a method on a subclass of converter?
86 ilabel = len(c.labels)
87 if label[0].isalpha():
88 # Either a symbol name or a named token
89 if label in c.symbol2number:
90 # A symbol name (a non-terminal)
91 if label in c.symbol2label:
92 return c.symbol2label[label]
93 else:
94 c.labels.append((c.symbol2number[label], None))
95 c.symbol2label[label] = ilabel
96 return ilabel
97 else:
98 # A named token (NAME, NUMBER, STRING)
99 itoken = getattr(token, label, None)
100 assert isinstance(itoken, int), label
101 assert itoken in token.tok_name, label
102 if itoken in c.tokens:
103 return c.tokens[itoken]
104 else:
105 c.labels.append((itoken, None))
106 c.tokens[itoken] = ilabel
107 return ilabel
108 else:
109 # Either a keyword or an operator
110 assert label[0] in ('"', "'"), label
111 value = eval(label)
112 if value[0].isalpha():
113 if label[0] == '"':
114 keywords = c.soft_keywords
115 else:
116 keywords = c.keywords
117
118 # A keyword
119 if value in keywords:
120 return keywords[value]
121 else:
122 c.labels.append((token.NAME, value))
123 keywords[value] = ilabel
124 return ilabel
125 else:
126 # An operator (any non-numeric token)
127 itoken = grammar.opmap[value] # Fails if unknown token
128 if itoken in c.tokens:
129 return c.tokens[itoken]
130 else:
131 c.labels.append((itoken, None))
132 c.tokens[itoken] = ilabel
133 return ilabel
134
135 def addfirstsets(self) -> None:
136 names = list(self.dfas.keys())
137 names.sort()
138 for name in names:
139 if name not in self.first:
140 self.calcfirst(name)
141 # print name, self.first[name].keys()
142
143 def calcfirst(self, name: str) -> None:
144 dfa = self.dfas[name]
145 self.first[name] = None # dummy to detect left recursion
146 state = dfa[0]
147 totalset: Dict[str, int] = {}
148 overlapcheck = {}
149 for label in state.arcs:
150 if label in self.dfas:
151 if label in self.first:
152 fset = self.first[label]
153 if fset is None:
154 raise ValueError("recursion for rule %r" % name)
155 else:
156 self.calcfirst(label)
157 fset = self.first[label]
158 assert fset is not None
159 totalset.update(fset)
160 overlapcheck[label] = fset
161 else:
162 totalset[label] = 1
163 overlapcheck[label] = {label: 1}
164 inverse: Dict[str, str] = {}
165 for label, itsfirst in overlapcheck.items():
166 for symbol in itsfirst:
167 if symbol in inverse:
168 raise ValueError(
169 "rule %s is ambiguous; %s is in the first sets of %s as well"
170 " as %s" % (name, symbol, label, inverse[symbol])
171 )
172 inverse[symbol] = label
173 self.first[name] = totalset
174
175 def parse(self) -> Tuple[Dict[str, List["DFAState"]], str]:
176 dfas = {}
177 startsymbol: Optional[str] = None
178 # MSTART: (NEWLINE | RULE)* ENDMARKER
179 while self.type != token.ENDMARKER:
180 while self.type == token.NEWLINE:
181 self.gettoken()
182 # RULE: NAME ':' RHS NEWLINE
183 name = self.expect(token.NAME)
184 self.expect(token.OP, ":")
185 a, z = self.parse_rhs()
186 self.expect(token.NEWLINE)
187 # self.dump_nfa(name, a, z)
188 dfa = self.make_dfa(a, z)
189 # self.dump_dfa(name, dfa)
190 # oldlen = len(dfa)
191 self.simplify_dfa(dfa)
192 # newlen = len(dfa)
193 dfas[name] = dfa
194 # print name, oldlen, newlen
195 if startsymbol is None:
196 startsymbol = name
197 assert startsymbol is not None
198 return dfas, startsymbol
199
200 def make_dfa(self, start: "NFAState", finish: "NFAState") -> List["DFAState"]:
201 # To turn an NFA into a DFA, we define the states of the DFA
202 # to correspond to *sets* of states of the NFA. Then do some
203 # state reduction. Let's represent sets as dicts with 1 for
204 # values.
205 assert isinstance(start, NFAState)
206 assert isinstance(finish, NFAState)
207
208 def closure(state: NFAState) -> Dict[NFAState, int]:
209 base: Dict[NFAState, int] = {}
210 addclosure(state, base)
211 return base
212
213 def addclosure(state: NFAState, base: Dict[NFAState, int]) -> None:
214 assert isinstance(state, NFAState)
215 if state in base:
216 return
217 base[state] = 1
218 for label, next in state.arcs:
219 if label is None:
220 addclosure(next, base)
221
222 states = [DFAState(closure(start), finish)]
223 for state in states: # NB states grows while we're iterating
224 arcs: Dict[str, Dict[NFAState, int]] = {}
225 for nfastate in state.nfaset:
226 for label, next in nfastate.arcs:
227 if label is not None:
228 addclosure(next, arcs.setdefault(label, {}))
229 for label, nfaset in sorted(arcs.items()):
230 for st in states:
231 if st.nfaset == nfaset:
232 break
233 else:
234 st = DFAState(nfaset, finish)
235 states.append(st)
236 state.addarc(st, label)
237 return states # List of DFAState instances; first one is start
238
239 def dump_nfa(self, name: str, start: "NFAState", finish: "NFAState") -> None:
240 print("Dump of NFA for", name)
241 todo = [start]
242 for i, state in enumerate(todo):
243 print(" State", i, state is finish and "(final)" or "")
244 for label, next in state.arcs:
245 if next in todo:
246 j = todo.index(next)
247 else:
248 j = len(todo)
249 todo.append(next)
250 if label is None:
251 print(" -> %d" % j)
252 else:
253 print(" %s -> %d" % (label, j))
254
255 def dump_dfa(self, name: str, dfa: Sequence["DFAState"]) -> None:
256 print("Dump of DFA for", name)
257 for i, state in enumerate(dfa):
258 print(" State", i, state.isfinal and "(final)" or "")
259 for label, next in sorted(state.arcs.items()):
260 print(" %s -> %d" % (label, dfa.index(next)))
261
262 def simplify_dfa(self, dfa: List["DFAState"]) -> None:
263 # This is not theoretically optimal, but works well enough.
264 # Algorithm: repeatedly look for two states that have the same
265 # set of arcs (same labels pointing to the same nodes) and
266 # unify them, until things stop changing.
267
268 # dfa is a list of DFAState instances
269 changes = True
270 while changes:
271 changes = False
272 for i, state_i in enumerate(dfa):
273 for j in range(i + 1, len(dfa)):
274 state_j = dfa[j]
275 if state_i == state_j:
276 # print " unify", i, j
277 del dfa[j]
278 for state in dfa:
279 state.unifystate(state_j, state_i)
280 changes = True
281 break
282
283 def parse_rhs(self) -> Tuple["NFAState", "NFAState"]:
284 # RHS: ALT ('|' ALT)*
285 a, z = self.parse_alt()
286 if self.value != "|":
287 return a, z
288 else:
289 aa = NFAState()
290 zz = NFAState()
291 aa.addarc(a)
292 z.addarc(zz)
293 while self.value == "|":
294 self.gettoken()
295 a, z = self.parse_alt()
296 aa.addarc(a)
297 z.addarc(zz)
298 return aa, zz
299
300 def parse_alt(self) -> Tuple["NFAState", "NFAState"]:
301 # ALT: ITEM+
302 a, b = self.parse_item()
303 while self.value in ("(", "[") or self.type in (token.NAME, token.STRING):
304 c, d = self.parse_item()
305 b.addarc(c)
306 b = d
307 return a, b
308
309 def parse_item(self) -> Tuple["NFAState", "NFAState"]:
310 # ITEM: '[' RHS ']' | ATOM ['+' | '*']
311 if self.value == "[":
312 self.gettoken()
313 a, z = self.parse_rhs()
314 self.expect(token.OP, "]")
315 a.addarc(z)
316 return a, z
317 else:
318 a, z = self.parse_atom()
319 value = self.value
320 if value not in ("+", "*"):
321 return a, z
322 self.gettoken()
323 z.addarc(a)
324 if value == "+":
325 return a, z
326 else:
327 return a, a
328
329 def parse_atom(self) -> Tuple["NFAState", "NFAState"]:
330 # ATOM: '(' RHS ')' | NAME | STRING
331 if self.value == "(":
332 self.gettoken()
333 a, z = self.parse_rhs()
334 self.expect(token.OP, ")")
335 return a, z
336 elif self.type in (token.NAME, token.STRING):
337 a = NFAState()
338 z = NFAState()
339 a.addarc(z, self.value)
340 self.gettoken()
341 return a, z
342 else:
343 self.raise_error(
344 "expected (...) or NAME or STRING, got %s/%s", self.type, self.value
345 )
346 raise AssertionError
347
348 def expect(self, type: int, value: Optional[Any] = None) -> str:
349 if self.type != type or (value is not None and self.value != value):
350 self.raise_error(
351 "expected %s/%s, got %s/%s", type, value, self.type, self.value
352 )
353 value = self.value
354 self.gettoken()
355 return value
356
357 def gettoken(self) -> None:
358 tup = next(self.generator)
359 while tup[0] in (tokenize.COMMENT, tokenize.NL):
360 tup = next(self.generator)
361 self.type, self.value, self.begin, self.end, self.line = tup
362 # print token.tok_name[self.type], repr(self.value)
363
364 def raise_error(self, msg: str, *args: Any) -> NoReturn:
365 if args:
366 try:
367 msg = msg % args
368 except Exception:
369 msg = " ".join([msg] + list(map(str, args)))
370 raise SyntaxError(msg, (self.filename, self.end[0], self.end[1], self.line))
371
372
373class NFAState:
374 arcs: List[Tuple[Optional[str], "NFAState"]]
375
376 def __init__(self) -> None:
377 self.arcs = [] # list of (label, NFAState) pairs
378
379 def addarc(self, next: "NFAState", label: Optional[str] = None) -> None:
380 assert label is None or isinstance(label, str)
381 assert isinstance(next, NFAState)
382 self.arcs.append((label, next))
383
384
385class DFAState:
386 nfaset: Dict[NFAState, Any]
387 isfinal: bool
388 arcs: Dict[str, "DFAState"]
389
390 def __init__(self, nfaset: Dict[NFAState, Any], final: NFAState) -> None:
391 assert isinstance(nfaset, dict)
392 assert isinstance(next(iter(nfaset)), NFAState)
393 assert isinstance(final, NFAState)
394 self.nfaset = nfaset
395 self.isfinal = final in nfaset
396 self.arcs = {} # map from label to DFAState
397
398 def addarc(self, next: "DFAState", label: str) -> None:
399 assert isinstance(label, str)
400 assert label not in self.arcs
401 assert isinstance(next, DFAState)
402 self.arcs[label] = next
403
404 def unifystate(self, old: "DFAState", new: "DFAState") -> None:
405 for label, next in self.arcs.items():
406 if next is old:
407 self.arcs[label] = new
408
409 def __eq__(self, other: Any) -> bool:
410 # Equality test -- ignore the nfaset instance variable
411 assert isinstance(other, DFAState)
412 if self.isfinal != other.isfinal:
413 return False
414 # Can't just return self.arcs == other.arcs, because that
415 # would invoke this method recursively, with cycles...
416 if len(self.arcs) != len(other.arcs):
417 return False
418 for label, next in self.arcs.items():
419 if next is not other.arcs.get(label):
420 return False
421 return True
422
423 __hash__: Any = None # For Py3 compatibility.
424
425
426def generate_grammar(filename: Path = "Grammar.txt") -> PgenGrammar:
427 p = ParserGenerator(filename)
428 return p.make_grammar()