This file is indexed.

/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()