/usr/lib/python3.6/lib2to3/pgen2/pgen.py is in python3-lib2to3 3.6.5-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 | # Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.
# Pgen imports
from . import grammar, token, tokenize
class PgenGrammar(grammar.Grammar):
pass
class ParserGenerator(object):
def __init__(self, filename, stream=None):
close_stream = None
if stream is None:
stream = open(filename)
close_stream = stream.close
self.filename = filename
self.stream = stream
self.generator = tokenize.generate_tokens(stream.readline)
self.gettoken() # Initialize lookahead
self.dfas, self.startsymbol = self.parse()
if close_stream is not None:
close_stream()
self.first = {} # map from symbol name to set of tokens
self.addfirstsets()
def make_grammar(self):
c = PgenGrammar()
names = list(self.dfas.keys())
names.sort()
names.remove(self.startsymbol)
names.insert(0, self.startsymbol)
for name in names:
i = 256 + len(c.symbol2number)
c.symbol2number[name] = i
c.number2symbol[i] = name
for name in names:
dfa = self.dfas[name]
states = []
for state in dfa:
arcs = []
for label, next in sorted(state.arcs.items()):
arcs.append((self.make_label(c, label), dfa.index(next)))
if state.isfinal:
arcs.append((0, dfa.index(state)))
states.append(arcs)
c.states.append(states)
c.dfas[c.symbol2number[name]] = (states, self.make_first(c, name))
c.start = c.symbol2number[self.startsymbol]
return c
def make_first(self, c, name):
rawfirst = self.first[name]
first = {}
for label in sorted(rawfirst):
ilabel = self.make_label(c, label)
##assert ilabel not in first # XXX failed on <> ... !=
first[ilabel] = 1
return first
def make_label(self, c, label):
# XXX Maybe this should be a method on a subclass of converter?
ilabel = len(c.labels)
if label[0].isalpha():
# Either a symbol name or a named token
if label in c.symbol2number:
# A symbol name (a non-terminal)
if label in c.symbol2label:
return c.symbol2label[label]
else:
c.labels.append((c.symbol2number[label], None))
c.symbol2label[label] = ilabel
return ilabel
else:
# A named token (NAME, NUMBER, STRING)
itoken = getattr(token, label, None)
assert isinstance(itoken, int), label
assert itoken in token.tok_name, label
if itoken in c.tokens:
return c.tokens[itoken]
else:
c.labels.append((itoken, None))
c.tokens[itoken] = ilabel
return ilabel
else:
# Either a keyword or an operator
assert label[0] in ('"', "'"), label
value = eval(label)
if value[0].isalpha():
# A keyword
if value in c.keywords:
return c.keywords[value]
else:
c.labels.append((token.NAME, value))
c.keywords[value] = ilabel
return ilabel
else:
# An operator (any non-numeric token)
itoken = grammar.opmap[value] # Fails if unknown token
if itoken in c.tokens:
return c.tokens[itoken]
else:
c.labels.append((itoken, None))
c.tokens[itoken] = ilabel
return ilabel
def addfirstsets(self):
names = list(self.dfas.keys())
names.sort()
for name in names:
if name not in self.first:
self.calcfirst(name)
#print name, self.first[name].keys()
def calcfirst(self, name):
dfa = self.dfas[name]
self.first[name] = None # dummy to detect left recursion
state = dfa[0]
totalset = {}
overlapcheck = {}
for label, next in state.arcs.items():
if label in self.dfas:
if label in self.first:
fset = self.first[label]
if fset is None:
raise ValueError("recursion for rule %r" % name)
else:
self.calcfirst(label)
fset = self.first[label]
totalset.update(fset)
overlapcheck[label] = fset
else:
totalset[label] = 1
overlapcheck[label] = {label: 1}
inverse = {}
for label, itsfirst in overlapcheck.items():
for symbol in itsfirst:
if symbol in inverse:
raise ValueError("rule %s is ambiguous; %s is in the"
" first sets of %s as well as %s" %
(name, symbol, label, inverse[symbol]))
inverse[symbol] = label
self.first[name] = totalset
def parse(self):
dfas = {}
startsymbol = None
# MSTART: (NEWLINE | RULE)* ENDMARKER
while self.type != token.ENDMARKER:
while self.type == token.NEWLINE:
self.gettoken()
# RULE: NAME ':' RHS NEWLINE
name = self.expect(token.NAME)
self.expect(token.OP, ":")
a, z = self.parse_rhs()
self.expect(token.NEWLINE)
#self.dump_nfa(name, a, z)
dfa = self.make_dfa(a, z)
#self.dump_dfa(name, dfa)
oldlen = len(dfa)
self.simplify_dfa(dfa)
newlen = len(dfa)
dfas[name] = dfa
#print name, oldlen, newlen
if startsymbol is None:
startsymbol = name
return dfas, startsymbol
def make_dfa(self, start, finish):
# To turn an NFA into a DFA, we define the states of the DFA
# to correspond to *sets* of states of the NFA. Then do some
# state reduction. Let's represent sets as dicts with 1 for
# values.
assert isinstance(start, NFAState)
assert isinstance(finish, NFAState)
def closure(state):
base = {}
addclosure(state, base)
return base
def addclosure(state, base):
assert isinstance(state, NFAState)
if state in base:
return
base[state] = 1
for label, next in state.arcs:
if label is None:
addclosure(next, base)
states = [DFAState(closure(start), finish)]
for state in states: # NB states grows while we're iterating
arcs = {}
for nfastate in state.nfaset:
for label, next in nfastate.arcs:
if label is not None:
addclosure(next, arcs.setdefault(label, {}))
for label, nfaset in sorted(arcs.items()):
for st in states:
if st.nfaset == nfaset:
break
else:
st = DFAState(nfaset, finish)
states.append(st)
state.addarc(st, label)
return states # List of DFAState instances; first one is start
def dump_nfa(self, name, start, finish):
print("Dump of NFA for", name)
todo = [start]
for i, state in enumerate(todo):
print(" State", i, state is finish and "(final)" or "")
for label, next in state.arcs:
if next in todo:
j = todo.index(next)
else:
j = len(todo)
todo.append(next)
if label is None:
print(" -> %d" % j)
else:
print(" %s -> %d" % (label, j))
def dump_dfa(self, name, dfa):
print("Dump of DFA for", name)
for i, state in enumerate(dfa):
print(" State", i, state.isfinal and "(final)" or "")
for label, next in sorted(state.arcs.items()):
print(" %s -> %d" % (label, dfa.index(next)))
def simplify_dfa(self, dfa):
# This is not theoretically optimal, but works well enough.
# Algorithm: repeatedly look for two states that have the same
# set of arcs (same labels pointing to the same nodes) and
# unify them, until things stop changing.
# dfa is a list of DFAState instances
changes = True
while changes:
changes = False
for i, state_i in enumerate(dfa):
for j in range(i+1, len(dfa)):
state_j = dfa[j]
if state_i == state_j:
#print " unify", i, j
del dfa[j]
for state in dfa:
state.unifystate(state_j, state_i)
changes = True
break
def parse_rhs(self):
# RHS: ALT ('|' ALT)*
a, z = self.parse_alt()
if self.value != "|":
return a, z
else:
aa = NFAState()
zz = NFAState()
aa.addarc(a)
z.addarc(zz)
while self.value == "|":
self.gettoken()
a, z = self.parse_alt()
aa.addarc(a)
z.addarc(zz)
return aa, zz
def parse_alt(self):
# ALT: ITEM+
a, b = self.parse_item()
while (self.value in ("(", "[") or
self.type in (token.NAME, token.STRING)):
c, d = self.parse_item()
b.addarc(c)
b = d
return a, b
def parse_item(self):
# ITEM: '[' RHS ']' | ATOM ['+' | '*']
if self.value == "[":
self.gettoken()
a, z = self.parse_rhs()
self.expect(token.OP, "]")
a.addarc(z)
return a, z
else:
a, z = self.parse_atom()
value = self.value
if value not in ("+", "*"):
return a, z
self.gettoken()
z.addarc(a)
if value == "+":
return a, z
else:
return a, a
def parse_atom(self):
# ATOM: '(' RHS ')' | NAME | STRING
if self.value == "(":
self.gettoken()
a, z = self.parse_rhs()
self.expect(token.OP, ")")
return a, z
elif self.type in (token.NAME, token.STRING):
a = NFAState()
z = NFAState()
a.addarc(z, self.value)
self.gettoken()
return a, z
else:
self.raise_error("expected (...) or NAME or STRING, got %s/%s",
self.type, self.value)
def expect(self, type, value=None):
if self.type != type or (value is not None and self.value != value):
self.raise_error("expected %s/%s, got %s/%s",
type, value, self.type, self.value)
value = self.value
self.gettoken()
return value
def gettoken(self):
tup = next(self.generator)
while tup[0] in (tokenize.COMMENT, tokenize.NL):
tup = next(self.generator)
self.type, self.value, self.begin, self.end, self.line = tup
#print token.tok_name[self.type], repr(self.value)
def raise_error(self, msg, *args):
if args:
try:
msg = msg % args
except:
msg = " ".join([msg] + list(map(str, args)))
raise SyntaxError(msg, (self.filename, self.end[0],
self.end[1], self.line))
class NFAState(object):
def __init__(self):
self.arcs = [] # list of (label, NFAState) pairs
def addarc(self, next, label=None):
assert label is None or isinstance(label, str)
assert isinstance(next, NFAState)
self.arcs.append((label, next))
class DFAState(object):
def __init__(self, nfaset, final):
assert isinstance(nfaset, dict)
assert isinstance(next(iter(nfaset)), NFAState)
assert isinstance(final, NFAState)
self.nfaset = nfaset
self.isfinal = final in nfaset
self.arcs = {} # map from label to DFAState
def addarc(self, next, label):
assert isinstance(label, str)
assert label not in self.arcs
assert isinstance(next, DFAState)
self.arcs[label] = next
def unifystate(self, old, new):
for label, next in self.arcs.items():
if next is old:
self.arcs[label] = new
def __eq__(self, other):
# Equality test -- ignore the nfaset instance variable
assert isinstance(other, DFAState)
if self.isfinal != other.isfinal:
return False
# Can't just return self.arcs == other.arcs, because that
# would invoke this method recursively, with cycles...
if len(self.arcs) != len(other.arcs):
return False
for label, next in self.arcs.items():
if next is not other.arcs.get(label):
return False
return True
__hash__ = None # For Py3 compatibility.
def generate_grammar(filename="Grammar.txt"):
p = ParserGenerator(filename)
return p.make_grammar()
|