1#
2# Secret Labs' Regular Expression Engine
3#
4# convert re-style regular expression to sre pattern
5#
6# Copyright (c) 1998-2001 by Secret Labs AB.  All rights reserved.
7#
8# See the sre.py file for information on usage and redistribution.
9#
10
11"""Internal support module for sre"""
12
13# XXX: show string offset and offending character for all errors
14
15import sys
16
17from sre_constants import *
18
19SPECIAL_CHARS = ".\\[{()*+?^$|"
20REPEAT_CHARS = "*+?{"
21
22DIGITS = set("0123456789")
23
24OCTDIGITS = set("01234567")
25HEXDIGITS = set("0123456789abcdefABCDEF")
26
27WHITESPACE = set(" \t\n\r\v\f")
28
29ESCAPES = {
30    r"\a": (LITERAL, ord("\a")),
31    r"\b": (LITERAL, ord("\b")),
32    r"\f": (LITERAL, ord("\f")),
33    r"\n": (LITERAL, ord("\n")),
34    r"\r": (LITERAL, ord("\r")),
35    r"\t": (LITERAL, ord("\t")),
36    r"\v": (LITERAL, ord("\v")),
37    r"\\": (LITERAL, ord("\\"))
38}
39
40CATEGORIES = {
41    r"\A": (AT, AT_BEGINNING_STRING), # start of string
42    r"\b": (AT, AT_BOUNDARY),
43    r"\B": (AT, AT_NON_BOUNDARY),
44    r"\d": (IN, [(CATEGORY, CATEGORY_DIGIT)]),
45    r"\D": (IN, [(CATEGORY, CATEGORY_NOT_DIGIT)]),
46    r"\s": (IN, [(CATEGORY, CATEGORY_SPACE)]),
47    r"\S": (IN, [(CATEGORY, CATEGORY_NOT_SPACE)]),
48    r"\w": (IN, [(CATEGORY, CATEGORY_WORD)]),
49    r"\W": (IN, [(CATEGORY, CATEGORY_NOT_WORD)]),
50    r"\Z": (AT, AT_END_STRING), # end of string
51}
52
53FLAGS = {
54    # standard flags
55    "i": SRE_FLAG_IGNORECASE,
56    "L": SRE_FLAG_LOCALE,
57    "m": SRE_FLAG_MULTILINE,
58    "s": SRE_FLAG_DOTALL,
59    "x": SRE_FLAG_VERBOSE,
60    # extensions
61    "t": SRE_FLAG_TEMPLATE,
62    "u": SRE_FLAG_UNICODE,
63}
64
65class Pattern:
66    # master pattern object.  keeps track of global attributes
67    def __init__(self):
68        self.flags = 0
69        self.open = []
70        self.groups = 1
71        self.groupdict = {}
72    def opengroup(self, name=None):
73        gid = self.groups
74        self.groups = gid + 1
75        if name is not None:
76            ogid = self.groupdict.get(name, None)
77            if ogid is not None:
78                raise error, ("redefinition of group name %s as group %d; "
79                              "was group %d" % (repr(name), gid,  ogid))
80            self.groupdict[name] = gid
81        self.open.append(gid)
82        return gid
83    def closegroup(self, gid):
84        self.open.remove(gid)
85    def checkgroup(self, gid):
86        return gid < self.groups and gid not in self.open
87
88class SubPattern:
89    # a subpattern, in intermediate form
90    def __init__(self, pattern, data=None):
91        self.pattern = pattern
92        if data is None:
93            data = []
94        self.data = data
95        self.width = None
96    def dump(self, level=0):
97        nl = 1
98        seqtypes = type(()), type([])
99        for op, av in self.data:
100            print level*"  " + op,; nl = 0
101            if op == "in":
102                # member sublanguage
103                print; nl = 1
104                for op, a in av:
105                    print (level+1)*"  " + op, a
106            elif op == "branch":
107                print; nl = 1
108                i = 0
109                for a in av[1]:
110                    if i > 0:
111                        print level*"  " + "or"
112                    a.dump(level+1); nl = 1
113                    i = i + 1
114            elif type(av) in seqtypes:
115                for a in av:
116                    if isinstance(a, SubPattern):
117                        if not nl: print
118                        a.dump(level+1); nl = 1
119                    else:
120                        print a, ; nl = 0
121            else:
122                print av, ; nl = 0
123            if not nl: print
124    def __repr__(self):
125        return repr(self.data)
126    def __len__(self):
127        return len(self.data)
128    def __delitem__(self, index):
129        del self.data[index]
130    def __getitem__(self, index):
131        if isinstance(index, slice):
132            return SubPattern(self.pattern, self.data[index])
133        return self.data[index]
134    def __setitem__(self, index, code):
135        self.data[index] = code
136    def insert(self, index, code):
137        self.data.insert(index, code)
138    def append(self, code):
139        self.data.append(code)
140    def getwidth(self):
141        # determine the width (min, max) for this subpattern
142        if self.width:
143            return self.width
144        lo = hi = 0L
145        UNITCODES = (ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY)
146        REPEATCODES = (MIN_REPEAT, MAX_REPEAT)
147        for op, av in self.data:
148            if op is BRANCH:
149                i = sys.maxint
150                j = 0
151                for av in av[1]:
152                    l, h = av.getwidth()
153                    i = min(i, l)
154                    j = max(j, h)
155                lo = lo + i
156                hi = hi + j
157            elif op is CALL:
158                i, j = av.getwidth()
159                lo = lo + i
160                hi = hi + j
161            elif op is SUBPATTERN:
162                i, j = av[1].getwidth()
163                lo = lo + i
164                hi = hi + j
165            elif op in REPEATCODES:
166                i, j = av[2].getwidth()
167                lo = lo + long(i) * av[0]
168                hi = hi + long(j) * av[1]
169            elif op in UNITCODES:
170                lo = lo + 1
171                hi = hi + 1
172            elif op == SUCCESS:
173                break
174        self.width = int(min(lo, sys.maxint)), int(min(hi, sys.maxint))
175        return self.width
176
177class Tokenizer:
178    def __init__(self, string):
179        self.string = string
180        self.index = 0
181        self.__next()
182    def __next(self):
183        if self.index >= len(self.string):
184            self.next = None
185            return
186        char = self.string[self.index]
187        if char[0] == "\\":
188            try:
189                c = self.string[self.index + 1]
190            except IndexError:
191                raise error, "bogus escape (end of line)"
192            char = char + c
193        self.index = self.index + len(char)
194        self.next = char
195    def match(self, char, skip=1):
196        if char == self.next:
197            if skip:
198                self.__next()
199            return 1
200        return 0
201    def get(self):
202        this = self.next
203        self.__next()
204        return this
205    def tell(self):
206        return self.index, self.next
207    def seek(self, index):
208        self.index, self.next = index
209
210def isident(char):
211    return "a" <= char <= "z" or "A" <= char <= "Z" or char == "_"
212
213def isdigit(char):
214    return "0" <= char <= "9"
215
216def isname(name):
217    # check that group name is a valid string
218    if not isident(name[0]):
219        return False
220    for char in name[1:]:
221        if not isident(char) and not isdigit(char):
222            return False
223    return True
224
225def _class_escape(source, escape):
226    # handle escape code inside character class
227    code = ESCAPES.get(escape)
228    if code:
229        return code
230    code = CATEGORIES.get(escape)
231    if code:
232        return code
233    try:
234        c = escape[1:2]
235        if c == "x":
236            # hexadecimal escape (exactly two digits)
237            while source.next in HEXDIGITS and len(escape) < 4:
238                escape = escape + source.get()
239            escape = escape[2:]
240            if len(escape) != 2:
241                raise error, "bogus escape: %s" % repr("\\" + escape)
242            return LITERAL, int(escape, 16) & 0xff
243        elif c in OCTDIGITS:
244            # octal escape (up to three digits)
245            while source.next in OCTDIGITS and len(escape) < 4:
246                escape = escape + source.get()
247            escape = escape[1:]
248            return LITERAL, int(escape, 8) & 0xff
249        elif c in DIGITS:
250            raise error, "bogus escape: %s" % repr(escape)
251        if len(escape) == 2:
252            return LITERAL, ord(escape[1])
253    except ValueError:
254        pass
255    raise error, "bogus escape: %s" % repr(escape)
256
257def _escape(source, escape, state):
258    # handle escape code in expression
259    code = CATEGORIES.get(escape)
260    if code:
261        return code
262    code = ESCAPES.get(escape)
263    if code:
264        return code
265    try:
266        c = escape[1:2]
267        if c == "x":
268            # hexadecimal escape
269            while source.next in HEXDIGITS and len(escape) < 4:
270                escape = escape + source.get()
271            if len(escape) != 4:
272                raise ValueError
273            return LITERAL, int(escape[2:], 16) & 0xff
274        elif c == "0":
275            # octal escape
276            while source.next in OCTDIGITS and len(escape) < 4:
277                escape = escape + source.get()
278            return LITERAL, int(escape[1:], 8) & 0xff
279        elif c in DIGITS:
280            # octal escape *or* decimal group reference (sigh)
281            if source.next in DIGITS:
282                escape = escape + source.get()
283                if (escape[1] in OCTDIGITS and escape[2] in OCTDIGITS and
284                    source.next in OCTDIGITS):
285                    # got three octal digits; this is an octal escape
286                    escape = escape + source.get()
287                    return LITERAL, int(escape[1:], 8) & 0xff
288            # not an octal escape, so this is a group reference
289            group = int(escape[1:])
290            if group < state.groups:
291                if not state.checkgroup(group):
292                    raise error, "cannot refer to open group"
293                return GROUPREF, group
294            raise ValueError
295        if len(escape) == 2:
296            return LITERAL, ord(escape[1])
297    except ValueError:
298        pass
299    raise error, "bogus escape: %s" % repr(escape)
300
301def _parse_sub(source, state, nested=1):
302    # parse an alternation: a|b|c
303
304    items = []
305    itemsappend = items.append
306    sourcematch = source.match
307    while 1:
308        itemsappend(_parse(source, state))
309        if sourcematch("|"):
310            continue
311        if not nested:
312            break
313        if not source.next or sourcematch(")", 0):
314            break
315        else:
316            raise error, "pattern not properly closed"
317
318    if len(items) == 1:
319        return items[0]
320
321    subpattern = SubPattern(state)
322    subpatternappend = subpattern.append
323
324    # check if all items share a common prefix
325    while 1:
326        prefix = None
327        for item in items:
328            if not item:
329                break
330            if prefix is None:
331                prefix = item[0]
332            elif item[0] != prefix:
333                break
334        else:
335            # all subitems start with a common "prefix".
336            # move it out of the branch
337            for item in items:
338                del item[0]
339            subpatternappend(prefix)
340            continue # check next one
341        break
342
343    # check if the branch can be replaced by a character set
344    for item in items:
345        if len(item) != 1 or item[0][0] != LITERAL:
346            break
347    else:
348        # we can store this as a character set instead of a
349        # branch (the compiler may optimize this even more)
350        set = []
351        setappend = set.append
352        for item in items:
353            setappend(item[0])
354        subpatternappend((IN, set))
355        return subpattern
356
357    subpattern.append((BRANCH, (None, items)))
358    return subpattern
359
360def _parse_sub_cond(source, state, condgroup):
361    item_yes = _parse(source, state)
362    if source.match("|"):
363        item_no = _parse(source, state)
364        if source.match("|"):
365            raise error, "conditional backref with more than two branches"
366    else:
367        item_no = None
368    if source.next and not source.match(")", 0):
369        raise error, "pattern not properly closed"
370    subpattern = SubPattern(state)
371    subpattern.append((GROUPREF_EXISTS, (condgroup, item_yes, item_no)))
372    return subpattern
373
374_PATTERNENDERS = set("|)")
375_ASSERTCHARS = set("=!<")
376_LOOKBEHINDASSERTCHARS = set("=!")
377_REPEATCODES = set([MIN_REPEAT, MAX_REPEAT])
378
379def _parse(source, state):
380    # parse a simple pattern
381    subpattern = SubPattern(state)
382
383    # precompute constants into local variables
384    subpatternappend = subpattern.append
385    sourceget = source.get
386    sourcematch = source.match
387    _len = len
388    PATTERNENDERS = _PATTERNENDERS
389    ASSERTCHARS = _ASSERTCHARS
390    LOOKBEHINDASSERTCHARS = _LOOKBEHINDASSERTCHARS
391    REPEATCODES = _REPEATCODES
392
393    while 1:
394
395        if source.next in PATTERNENDERS:
396            break # end of subpattern
397        this = sourceget()
398        if this is None:
399            break # end of pattern
400
401        if state.flags & SRE_FLAG_VERBOSE:
402            # skip whitespace and comments
403            if this in WHITESPACE:
404                continue
405            if this == "#":
406                while 1:
407                    this = sourceget()
408                    if this in (None, "\n"):
409                        break
410                continue
411
412        if this and this[0] not in SPECIAL_CHARS:
413            subpatternappend((LITERAL, ord(this)))
414
415        elif this == "[":
416            # character set
417            set = []
418            setappend = set.append
419##          if sourcematch(":"):
420##              pass # handle character classes
421            if sourcematch("^"):
422                setappend((NEGATE, None))
423            # check remaining characters
424            start = set[:]
425            while 1:
426                this = sourceget()
427                if this == "]" and set != start:
428                    break
429                elif this and this[0] == "\\":
430                    code1 = _class_escape(source, this)
431                elif this:
432                    code1 = LITERAL, ord(this)
433                else:
434                    raise error, "unexpected end of regular expression"
435                if sourcematch("-"):
436                    # potential range
437                    this = sourceget()
438                    if this == "]":
439                        if code1[0] is IN:
440                            code1 = code1[1][0]
441                        setappend(code1)
442                        setappend((LITERAL, ord("-")))
443                        break
444                    elif this:
445                        if this[0] == "\\":
446                            code2 = _class_escape(source, this)
447                        else:
448                            code2 = LITERAL, ord(this)
449                        if code1[0] != LITERAL or code2[0] != LITERAL:
450                            raise error, "bad character range"
451                        lo = code1[1]
452                        hi = code2[1]
453                        if hi < lo:
454                            raise error, "bad character range"
455                        setappend((RANGE, (lo, hi)))
456                    else:
457                        raise error, "unexpected end of regular expression"
458                else:
459                    if code1[0] is IN:
460                        code1 = code1[1][0]
461                    setappend(code1)
462
463            # XXX: <fl> should move set optimization to compiler!
464            if _len(set)==1 and set[0][0] is LITERAL:
465                subpatternappend(set[0]) # optimization
466            elif _len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL:
467                subpatternappend((NOT_LITERAL, set[1][1])) # optimization
468            else:
469                # XXX: <fl> should add charmap optimization here
470                subpatternappend((IN, set))
471
472        elif this and this[0] in REPEAT_CHARS:
473            # repeat previous item
474            if this == "?":
475                min, max = 0, 1
476            elif this == "*":
477                min, max = 0, MAXREPEAT
478
479            elif this == "+":
480                min, max = 1, MAXREPEAT
481            elif this == "{":
482                if source.next == "}":
483                    subpatternappend((LITERAL, ord(this)))
484                    continue
485                here = source.tell()
486                min, max = 0, MAXREPEAT
487                lo = hi = ""
488                while source.next in DIGITS:
489                    lo = lo + source.get()
490                if sourcematch(","):
491                    while source.next in DIGITS:
492                        hi = hi + sourceget()
493                else:
494                    hi = lo
495                if not sourcematch("}"):
496                    subpatternappend((LITERAL, ord(this)))
497                    source.seek(here)
498                    continue
499                if lo:
500                    min = int(lo)
501                if hi:
502                    max = int(hi)
503                if max < min:
504                    raise error, "bad repeat interval"
505            else:
506                raise error, "not supported"
507            # figure out which item to repeat
508            if subpattern:
509                item = subpattern[-1:]
510            else:
511                item = None
512            if not item or (_len(item) == 1 and item[0][0] == AT):
513                raise error, "nothing to repeat"
514            if item[0][0] in REPEATCODES:
515                raise error, "multiple repeat"
516            if sourcematch("?"):
517                subpattern[-1] = (MIN_REPEAT, (min, max, item))
518            else:
519                subpattern[-1] = (MAX_REPEAT, (min, max, item))
520
521        elif this == ".":
522            subpatternappend((ANY, None))
523
524        elif this == "(":
525            group = 1
526            name = None
527            condgroup = None
528            if sourcematch("?"):
529                group = 0
530                # options
531                if sourcematch("P"):
532                    # python extensions
533                    if sourcematch("<"):
534                        # named group: skip forward to end of name
535                        name = ""
536                        while 1:
537                            char = sourceget()
538                            if char is None:
539                                raise error, "unterminated name"
540                            if char == ">":
541                                break
542                            name = name + char
543                        group = 1
544                        if not isname(name):
545                            raise error, "bad character in group name"
546                    elif sourcematch("="):
547                        # named backreference
548                        name = ""
549                        while 1:
550                            char = sourceget()
551                            if char is None:
552                                raise error, "unterminated name"
553                            if char == ")":
554                                break
555                            name = name + char
556                        if not isname(name):
557                            raise error, "bad character in group name"
558                        gid = state.groupdict.get(name)
559                        if gid is None:
560                            raise error, "unknown group name"
561                        subpatternappend((GROUPREF, gid))
562                        continue
563                    else:
564                        char = sourceget()
565                        if char is None:
566                            raise error, "unexpected end of pattern"
567                        raise error, "unknown specifier: ?P%s" % char
568                elif sourcematch(":"):
569                    # non-capturing group
570                    group = 2
571                elif sourcematch("#"):
572                    # comment
573                    while 1:
574                        if source.next is None or source.next == ")":
575                            break
576                        sourceget()
577                    if not sourcematch(")"):
578                        raise error, "unbalanced parenthesis"
579                    continue
580                elif source.next in ASSERTCHARS:
581                    # lookahead assertions
582                    char = sourceget()
583                    dir = 1
584                    if char == "<":
585                        if source.next not in LOOKBEHINDASSERTCHARS:
586                            raise error, "syntax error"
587                        dir = -1 # lookbehind
588                        char = sourceget()
589                    p = _parse_sub(source, state)
590                    if not sourcematch(")"):
591                        raise error, "unbalanced parenthesis"
592                    if char == "=":
593                        subpatternappend((ASSERT, (dir, p)))
594                    else:
595                        subpatternappend((ASSERT_NOT, (dir, p)))
596                    continue
597                elif sourcematch("("):
598                    # conditional backreference group
599                    condname = ""
600                    while 1:
601                        char = sourceget()
602                        if char is None:
603                            raise error, "unterminated name"
604                        if char == ")":
605                            break
606                        condname = condname + char
607                    group = 2
608                    if isname(condname):
609                        condgroup = state.groupdict.get(condname)
610                        if condgroup is None:
611                            raise error, "unknown group name"
612                    else:
613                        try:
614                            condgroup = int(condname)
615                        except ValueError:
616                            raise error, "bad character in group name"
617                else:
618                    # flags
619                    if not source.next in FLAGS:
620                        raise error, "unexpected end of pattern"
621                    while source.next in FLAGS:
622                        state.flags = state.flags | FLAGS[sourceget()]
623            if group:
624                # parse group contents
625                if group == 2:
626                    # anonymous group
627                    group = None
628                else:
629                    group = state.opengroup(name)
630                if condgroup:
631                    p = _parse_sub_cond(source, state, condgroup)
632                else:
633                    p = _parse_sub(source, state)
634                if not sourcematch(")"):
635                    raise error, "unbalanced parenthesis"
636                if group is not None:
637                    state.closegroup(group)
638                subpatternappend((SUBPATTERN, (group, p)))
639            else:
640                while 1:
641                    char = sourceget()
642                    if char is None:
643                        raise error, "unexpected end of pattern"
644                    if char == ")":
645                        break
646                    raise error, "unknown extension"
647
648        elif this == "^":
649            subpatternappend((AT, AT_BEGINNING))
650
651        elif this == "$":
652            subpattern.append((AT, AT_END))
653
654        elif this and this[0] == "\\":
655            code = _escape(source, this, state)
656            subpatternappend(code)
657
658        else:
659            raise error, "parser error"
660
661    return subpattern
662
663def parse(str, flags=0, pattern=None):
664    # parse 're' pattern into list of (opcode, argument) tuples
665
666    source = Tokenizer(str)
667
668    if pattern is None:
669        pattern = Pattern()
670    pattern.flags = flags
671    pattern.str = str
672
673    p = _parse_sub(source, pattern, 0)
674
675    tail = source.get()
676    if tail == ")":
677        raise error, "unbalanced parenthesis"
678    elif tail:
679        raise error, "bogus characters at end of regular expression"
680
681    if flags & SRE_FLAG_DEBUG:
682        p.dump()
683
684    if not (flags & SRE_FLAG_VERBOSE) and p.pattern.flags & SRE_FLAG_VERBOSE:
685        # the VERBOSE flag was switched on inside the pattern.  to be
686        # on the safe side, we'll parse the whole thing again...
687        return parse(str, p.pattern.flags)
688
689    return p
690
691def parse_template(source, pattern):
692    # parse 're' replacement string into list of literals and
693    # group references
694    s = Tokenizer(source)
695    sget = s.get
696    p = []
697    a = p.append
698    def literal(literal, p=p, pappend=a):
699        if p and p[-1][0] is LITERAL:
700            p[-1] = LITERAL, p[-1][1] + literal
701        else:
702            pappend((LITERAL, literal))
703    sep = source[:0]
704    if type(sep) is type(""):
705        makechar = chr
706    else:
707        makechar = unichr
708    while 1:
709        this = sget()
710        if this is None:
711            break # end of replacement string
712        if this and this[0] == "\\":
713            # group
714            c = this[1:2]
715            if c == "g":
716                name = ""
717                if s.match("<"):
718                    while 1:
719                        char = sget()
720                        if char is None:
721                            raise error, "unterminated group name"
722                        if char == ">":
723                            break
724                        name = name + char
725                if not name:
726                    raise error, "bad group name"
727                try:
728                    index = int(name)
729                    if index < 0:
730                        raise error, "negative group number"
731                except ValueError:
732                    if not isname(name):
733                        raise error, "bad character in group name"
734                    try:
735                        index = pattern.groupindex[name]
736                    except KeyError:
737                        raise IndexError, "unknown group name"
738                a((MARK, index))
739            elif c == "0":
740                if s.next in OCTDIGITS:
741                    this = this + sget()
742                    if s.next in OCTDIGITS:
743                        this = this + sget()
744                literal(makechar(int(this[1:], 8) & 0xff))
745            elif c in DIGITS:
746                isoctal = False
747                if s.next in DIGITS:
748                    this = this + sget()
749                    if (c in OCTDIGITS and this[2] in OCTDIGITS and
750                        s.next in OCTDIGITS):
751                        this = this + sget()
752                        isoctal = True
753                        literal(makechar(int(this[1:], 8) & 0xff))
754                if not isoctal:
755                    a((MARK, int(this[1:])))
756            else:
757                try:
758                    this = makechar(ESCAPES[this][1])
759                except KeyError:
760                    pass
761                literal(this)
762        else:
763            literal(this)
764    # convert template to groups and literals lists
765    i = 0
766    groups = []
767    groupsappend = groups.append
768    literals = [None] * len(p)
769    for c, s in p:
770        if c is MARK:
771            groupsappend((i, s))
772            # literal[i] is already None
773        else:
774            literals[i] = s
775        i = i + 1
776    return groups, literals
777
778def expand_template(template, match):
779    g = match.group
780    sep = match.string[:0]
781    groups, literals = template
782    literals = literals[:]
783    try:
784        for index, group in groups:
785            literals[index] = s = g(group)
786            if s is None:
787                raise error, "unmatched group"
788    except IndexError:
789        raise error, "invalid group reference"
790    return sep.join(literals)
791