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 *
18from _sre import MAXREPEAT
19
20SPECIAL_CHARS = ".\\[{()*+?^$|"
21REPEAT_CHARS = "*+?{"
22
23DIGITS = set("0123456789")
24
25OCTDIGITS = set("01234567")
26HEXDIGITS = set("0123456789abcdefABCDEF")
27
28WHITESPACE = set(" \t\n\r\v\f")
29
30ESCAPES = {
31    r"\a": (LITERAL, ord("\a")),
32    r"\b": (LITERAL, ord("\b")),
33    r"\f": (LITERAL, ord("\f")),
34    r"\n": (LITERAL, ord("\n")),
35    r"\r": (LITERAL, ord("\r")),
36    r"\t": (LITERAL, ord("\t")),
37    r"\v": (LITERAL, ord("\v")),
38    r"\\": (LITERAL, ord("\\"))
39}
40
41CATEGORIES = {
42    r"\A": (AT, AT_BEGINNING_STRING), # start of string
43    r"\b": (AT, AT_BOUNDARY),
44    r"\B": (AT, AT_NON_BOUNDARY),
45    r"\d": (IN, [(CATEGORY, CATEGORY_DIGIT)]),
46    r"\D": (IN, [(CATEGORY, CATEGORY_NOT_DIGIT)]),
47    r"\s": (IN, [(CATEGORY, CATEGORY_SPACE)]),
48    r"\S": (IN, [(CATEGORY, CATEGORY_NOT_SPACE)]),
49    r"\w": (IN, [(CATEGORY, CATEGORY_WORD)]),
50    r"\W": (IN, [(CATEGORY, CATEGORY_NOT_WORD)]),
51    r"\Z": (AT, AT_END_STRING), # end of string
52}
53
54FLAGS = {
55    # standard flags
56    "i": SRE_FLAG_IGNORECASE,
57    "L": SRE_FLAG_LOCALE,
58    "m": SRE_FLAG_MULTILINE,
59    "s": SRE_FLAG_DOTALL,
60    "x": SRE_FLAG_VERBOSE,
61    # extensions
62    "t": SRE_FLAG_TEMPLATE,
63    "u": SRE_FLAG_UNICODE,
64}
65
66class Pattern:
67    # master pattern object.  keeps track of global attributes
68    def __init__(self):
69        self.flags = 0
70        self.open = []
71        self.groups = 1
72        self.groupdict = {}
73    def opengroup(self, name=None):
74        gid = self.groups
75        self.groups = gid + 1
76        if name is not None:
77            ogid = self.groupdict.get(name, None)
78            if ogid is not None:
79                raise error, ("redefinition of group name %s as group %d; "
80                              "was group %d" % (repr(name), gid,  ogid))
81            self.groupdict[name] = gid
82        self.open.append(gid)
83        return gid
84    def closegroup(self, gid):
85        self.open.remove(gid)
86    def checkgroup(self, gid):
87        return gid < self.groups and gid not in self.open
88
89class SubPattern:
90    # a subpattern, in intermediate form
91    def __init__(self, pattern, data=None):
92        self.pattern = pattern
93        if data is None:
94            data = []
95        self.data = data
96        self.width = None
97    def dump(self, level=0):
98        nl = 1
99        seqtypes = type(()), type([])
100        for op, av in self.data:
101            print level*"  " + op,; nl = 0
102            if op == "in":
103                # member sublanguage
104                print; nl = 1
105                for op, a in av:
106                    print (level+1)*"  " + op, a
107            elif op == "branch":
108                print; nl = 1
109                i = 0
110                for a in av[1]:
111                    if i > 0:
112                        print level*"  " + "or"
113                    a.dump(level+1); nl = 1
114                    i = i + 1
115            elif type(av) in seqtypes:
116                for a in av:
117                    if isinstance(a, SubPattern):
118                        if not nl: print
119                        a.dump(level+1); nl = 1
120                    else:
121                        print a, ; nl = 0
122            else:
123                print av, ; nl = 0
124            if not nl: print
125    def __repr__(self):
126        return repr(self.data)
127    def __len__(self):
128        return len(self.data)
129    def __delitem__(self, index):
130        del self.data[index]
131    def __getitem__(self, index):
132        if isinstance(index, slice):
133            return SubPattern(self.pattern, self.data[index])
134        return self.data[index]
135    def __setitem__(self, index, code):
136        self.data[index] = code
137    def insert(self, index, code):
138        self.data.insert(index, code)
139    def append(self, code):
140        self.data.append(code)
141    def getwidth(self):
142        # determine the width (min, max) for this subpattern
143        if self.width:
144            return self.width
145        lo = hi = 0L
146        UNITCODES = (ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY)
147        REPEATCODES = (MIN_REPEAT, MAX_REPEAT)
148        for op, av in self.data:
149            if op is BRANCH:
150                i = sys.maxint
151                j = 0
152                for av in av[1]:
153                    l, h = av.getwidth()
154                    i = min(i, l)
155                    j = max(j, h)
156                lo = lo + i
157                hi = hi + j
158            elif op is CALL:
159                i, j = av.getwidth()
160                lo = lo + i
161                hi = hi + j
162            elif op is SUBPATTERN:
163                i, j = av[1].getwidth()
164                lo = lo + i
165                hi = hi + j
166            elif op in REPEATCODES:
167                i, j = av[2].getwidth()
168                lo = lo + long(i) * av[0]
169                hi = hi + long(j) * av[1]
170            elif op in UNITCODES:
171                lo = lo + 1
172                hi = hi + 1
173            elif op == SUCCESS:
174                break
175        self.width = int(min(lo, sys.maxint)), int(min(hi, sys.maxint))
176        return self.width
177
178class Tokenizer:
179    def __init__(self, string):
180        self.string = string
181        self.index = 0
182        self.__next()
183    def __next(self):
184        if self.index >= len(self.string):
185            self.next = None
186            return
187        char = self.string[self.index]
188        if char[0] == "\\":
189            try:
190                c = self.string[self.index + 1]
191            except IndexError:
192                raise error, "bogus escape (end of line)"
193            char = char + c
194        self.index = self.index + len(char)
195        self.next = char
196    def match(self, char, skip=1):
197        if char == self.next:
198            if skip:
199                self.__next()
200            return 1
201        return 0
202    def get(self):
203        this = self.next
204        self.__next()
205        return this
206    def tell(self):
207        return self.index, self.next
208    def seek(self, index):
209        self.index, self.next = index
210
211def isident(char):
212    return "a" <= char <= "z" or "A" <= char <= "Z" or char == "_"
213
214def isdigit(char):
215    return "0" <= char <= "9"
216
217def isname(name):
218    # check that group name is a valid string
219    if not isident(name[0]):
220        return False
221    for char in name[1:]:
222        if not isident(char) and not isdigit(char):
223            return False
224    return True
225
226def _class_escape(source, escape):
227    # handle escape code inside character class
228    code = ESCAPES.get(escape)
229    if code:
230        return code
231    code = CATEGORIES.get(escape)
232    if code and code[0] == IN:
233        return code
234    try:
235        c = escape[1:2]
236        if c == "x":
237            # hexadecimal escape (exactly two digits)
238            while source.next in HEXDIGITS and len(escape) < 4:
239                escape = escape + source.get()
240            escape = escape[2:]
241            if len(escape) != 2:
242                raise error, "bogus escape: %s" % repr("\\" + escape)
243            return LITERAL, int(escape, 16) & 0xff
244        elif c in OCTDIGITS:
245            # octal escape (up to three digits)
246            while source.next in OCTDIGITS and len(escape) < 4:
247                escape = escape + source.get()
248            escape = escape[1:]
249            return LITERAL, int(escape, 8) & 0xff
250        elif c in DIGITS:
251            raise error, "bogus escape: %s" % repr(escape)
252        if len(escape) == 2:
253            return LITERAL, ord(escape[1])
254    except ValueError:
255        pass
256    raise error, "bogus escape: %s" % repr(escape)
257
258def _escape(source, escape, state):
259    # handle escape code in expression
260    code = CATEGORIES.get(escape)
261    if code:
262        return code
263    code = ESCAPES.get(escape)
264    if code:
265        return code
266    try:
267        c = escape[1:2]
268        if c == "x":
269            # hexadecimal escape
270            while source.next in HEXDIGITS and len(escape) < 4:
271                escape = escape + source.get()
272            if len(escape) != 4:
273                raise ValueError
274            return LITERAL, int(escape[2:], 16) & 0xff
275        elif c == "0":
276            # octal escape
277            while source.next in OCTDIGITS and len(escape) < 4:
278                escape = escape + source.get()
279            return LITERAL, int(escape[1:], 8) & 0xff
280        elif c in DIGITS:
281            # octal escape *or* decimal group reference (sigh)
282            if source.next in DIGITS:
283                escape = escape + source.get()
284                if (escape[1] in OCTDIGITS and escape[2] in OCTDIGITS and
285                    source.next in OCTDIGITS):
286                    # got three octal digits; this is an octal escape
287                    escape = escape + source.get()
288                    return LITERAL, int(escape[1:], 8) & 0xff
289            # not an octal escape, so this is a group reference
290            group = int(escape[1:])
291            if group < state.groups:
292                if not state.checkgroup(group):
293                    raise error, "cannot refer to open group"
294                return GROUPREF, group
295            raise ValueError
296        if len(escape) == 2:
297            return LITERAL, ord(escape[1])
298    except ValueError:
299        pass
300    raise error, "bogus escape: %s" % repr(escape)
301
302def _parse_sub(source, state, nested=1):
303    # parse an alternation: a|b|c
304
305    items = []
306    itemsappend = items.append
307    sourcematch = source.match
308    while 1:
309        itemsappend(_parse(source, state))
310        if sourcematch("|"):
311            continue
312        if not nested:
313            break
314        if not source.next or sourcematch(")", 0):
315            break
316        else:
317            raise error, "pattern not properly closed"
318
319    if len(items) == 1:
320        return items[0]
321
322    subpattern = SubPattern(state)
323    subpatternappend = subpattern.append
324
325    # check if all items share a common prefix
326    while 1:
327        prefix = None
328        for item in items:
329            if not item:
330                break
331            if prefix is None:
332                prefix = item[0]
333            elif item[0] != prefix:
334                break
335        else:
336            # all subitems start with a common "prefix".
337            # move it out of the branch
338            for item in items:
339                del item[0]
340            subpatternappend(prefix)
341            continue # check next one
342        break
343
344    # check if the branch can be replaced by a character set
345    for item in items:
346        if len(item) != 1 or item[0][0] != LITERAL:
347            break
348    else:
349        # we can store this as a character set instead of a
350        # branch (the compiler may optimize this even more)
351        set = []
352        setappend = set.append
353        for item in items:
354            setappend(item[0])
355        subpatternappend((IN, set))
356        return subpattern
357
358    subpattern.append((BRANCH, (None, items)))
359    return subpattern
360
361def _parse_sub_cond(source, state, condgroup):
362    item_yes = _parse(source, state)
363    if source.match("|"):
364        item_no = _parse(source, state)
365        if source.match("|"):
366            raise error, "conditional backref with more than two branches"
367    else:
368        item_no = None
369    if source.next and not source.match(")", 0):
370        raise error, "pattern not properly closed"
371    subpattern = SubPattern(state)
372    subpattern.append((GROUPREF_EXISTS, (condgroup, item_yes, item_no)))
373    return subpattern
374
375_PATTERNENDERS = set("|)")
376_ASSERTCHARS = set("=!<")
377_LOOKBEHINDASSERTCHARS = set("=!")
378_REPEATCODES = set([MIN_REPEAT, MAX_REPEAT])
379
380def _parse(source, state):
381    # parse a simple pattern
382    subpattern = SubPattern(state)
383
384    # precompute constants into local variables
385    subpatternappend = subpattern.append
386    sourceget = source.get
387    sourcematch = source.match
388    _len = len
389    PATTERNENDERS = _PATTERNENDERS
390    ASSERTCHARS = _ASSERTCHARS
391    LOOKBEHINDASSERTCHARS = _LOOKBEHINDASSERTCHARS
392    REPEATCODES = _REPEATCODES
393
394    while 1:
395
396        if source.next in PATTERNENDERS:
397            break # end of subpattern
398        this = sourceget()
399        if this is None:
400            break # end of pattern
401
402        if state.flags & SRE_FLAG_VERBOSE:
403            # skip whitespace and comments
404            if this in WHITESPACE:
405                continue
406            if this == "#":
407                while 1:
408                    this = sourceget()
409                    if this in (None, "\n"):
410                        break
411                continue
412
413        if this and this[0] not in SPECIAL_CHARS:
414            subpatternappend((LITERAL, ord(this)))
415
416        elif this == "[":
417            # character set
418            set = []
419            setappend = set.append
420##          if sourcematch(":"):
421##              pass # handle character classes
422            if sourcematch("^"):
423                setappend((NEGATE, None))
424            # check remaining characters
425            start = set[:]
426            while 1:
427                this = sourceget()
428                if this == "]" and set != start:
429                    break
430                elif this and this[0] == "\\":
431                    code1 = _class_escape(source, this)
432                elif this:
433                    code1 = LITERAL, ord(this)
434                else:
435                    raise error, "unexpected end of regular expression"
436                if sourcematch("-"):
437                    # potential range
438                    this = sourceget()
439                    if this == "]":
440                        if code1[0] is IN:
441                            code1 = code1[1][0]
442                        setappend(code1)
443                        setappend((LITERAL, ord("-")))
444                        break
445                    elif this:
446                        if this[0] == "\\":
447                            code2 = _class_escape(source, this)
448                        else:
449                            code2 = LITERAL, ord(this)
450                        if code1[0] != LITERAL or code2[0] != LITERAL:
451                            raise error, "bad character range"
452                        lo = code1[1]
453                        hi = code2[1]
454                        if hi < lo:
455                            raise error, "bad character range"
456                        setappend((RANGE, (lo, hi)))
457                    else:
458                        raise error, "unexpected end of regular expression"
459                else:
460                    if code1[0] is IN:
461                        code1 = code1[1][0]
462                    setappend(code1)
463
464            # XXX: <fl> should move set optimization to compiler!
465            if _len(set)==1 and set[0][0] is LITERAL:
466                subpatternappend(set[0]) # optimization
467            elif _len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL:
468                subpatternappend((NOT_LITERAL, set[1][1])) # optimization
469            else:
470                # XXX: <fl> should add charmap optimization here
471                subpatternappend((IN, set))
472
473        elif this and this[0] in REPEAT_CHARS:
474            # repeat previous item
475            if this == "?":
476                min, max = 0, 1
477            elif this == "*":
478                min, max = 0, MAXREPEAT
479
480            elif this == "+":
481                min, max = 1, MAXREPEAT
482            elif this == "{":
483                if source.next == "}":
484                    subpatternappend((LITERAL, ord(this)))
485                    continue
486                here = source.tell()
487                min, max = 0, MAXREPEAT
488                lo = hi = ""
489                while source.next in DIGITS:
490                    lo = lo + source.get()
491                if sourcematch(","):
492                    while source.next in DIGITS:
493                        hi = hi + sourceget()
494                else:
495                    hi = lo
496                if not sourcematch("}"):
497                    subpatternappend((LITERAL, ord(this)))
498                    source.seek(here)
499                    continue
500                if lo:
501                    min = int(lo)
502                    if min >= MAXREPEAT:
503                        raise OverflowError("the repetition number is too large")
504                if hi:
505                    max = int(hi)
506                    if max >= MAXREPEAT:
507                        raise OverflowError("the repetition number is too large")
508                    if max < min:
509                        raise error("bad repeat interval")
510            else:
511                raise error, "not supported"
512            # figure out which item to repeat
513            if subpattern:
514                item = subpattern[-1:]
515            else:
516                item = None
517            if not item or (_len(item) == 1 and item[0][0] == AT):
518                raise error, "nothing to repeat"
519            if item[0][0] in REPEATCODES:
520                raise error, "multiple repeat"
521            if sourcematch("?"):
522                subpattern[-1] = (MIN_REPEAT, (min, max, item))
523            else:
524                subpattern[-1] = (MAX_REPEAT, (min, max, item))
525
526        elif this == ".":
527            subpatternappend((ANY, None))
528
529        elif this == "(":
530            group = 1
531            name = None
532            condgroup = None
533            if sourcematch("?"):
534                group = 0
535                # options
536                if sourcematch("P"):
537                    # python extensions
538                    if sourcematch("<"):
539                        # named group: skip forward to end of name
540                        name = ""
541                        while 1:
542                            char = sourceget()
543                            if char is None:
544                                raise error, "unterminated name"
545                            if char == ">":
546                                break
547                            name = name + char
548                        group = 1
549                        if not name:
550                            raise error("missing group name")
551                        if not isname(name):
552                            raise error("bad character in group name %r" %
553                                        name)
554                    elif sourcematch("="):
555                        # named backreference
556                        name = ""
557                        while 1:
558                            char = sourceget()
559                            if char is None:
560                                raise error, "unterminated name"
561                            if char == ")":
562                                break
563                            name = name + char
564                        if not name:
565                            raise error("missing group name")
566                        if not isname(name):
567                            raise error("bad character in backref group name "
568                                        "%r" % name)
569                        gid = state.groupdict.get(name)
570                        if gid is None:
571                            raise error, "unknown group name"
572                        subpatternappend((GROUPREF, gid))
573                        continue
574                    else:
575                        char = sourceget()
576                        if char is None:
577                            raise error, "unexpected end of pattern"
578                        raise error, "unknown specifier: ?P%s" % char
579                elif sourcematch(":"):
580                    # non-capturing group
581                    group = 2
582                elif sourcematch("#"):
583                    # comment
584                    while 1:
585                        if source.next is None or source.next == ")":
586                            break
587                        sourceget()
588                    if not sourcematch(")"):
589                        raise error, "unbalanced parenthesis"
590                    continue
591                elif source.next in ASSERTCHARS:
592                    # lookahead assertions
593                    char = sourceget()
594                    dir = 1
595                    if char == "<":
596                        if source.next not in LOOKBEHINDASSERTCHARS:
597                            raise error, "syntax error"
598                        dir = -1 # lookbehind
599                        char = sourceget()
600                    p = _parse_sub(source, state)
601                    if not sourcematch(")"):
602                        raise error, "unbalanced parenthesis"
603                    if char == "=":
604                        subpatternappend((ASSERT, (dir, p)))
605                    else:
606                        subpatternappend((ASSERT_NOT, (dir, p)))
607                    continue
608                elif sourcematch("("):
609                    # conditional backreference group
610                    condname = ""
611                    while 1:
612                        char = sourceget()
613                        if char is None:
614                            raise error, "unterminated name"
615                        if char == ")":
616                            break
617                        condname = condname + char
618                    group = 2
619                    if not condname:
620                        raise error("missing group name")
621                    if isname(condname):
622                        condgroup = state.groupdict.get(condname)
623                        if condgroup is None:
624                            raise error, "unknown group name"
625                    else:
626                        try:
627                            condgroup = int(condname)
628                        except ValueError:
629                            raise error, "bad character in group name"
630                else:
631                    # flags
632                    if not source.next in FLAGS:
633                        raise error, "unexpected end of pattern"
634                    while source.next in FLAGS:
635                        state.flags = state.flags | FLAGS[sourceget()]
636            if group:
637                # parse group contents
638                if group == 2:
639                    # anonymous group
640                    group = None
641                else:
642                    group = state.opengroup(name)
643                if condgroup:
644                    p = _parse_sub_cond(source, state, condgroup)
645                else:
646                    p = _parse_sub(source, state)
647                if not sourcematch(")"):
648                    raise error, "unbalanced parenthesis"
649                if group is not None:
650                    state.closegroup(group)
651                subpatternappend((SUBPATTERN, (group, p)))
652            else:
653                while 1:
654                    char = sourceget()
655                    if char is None:
656                        raise error, "unexpected end of pattern"
657                    if char == ")":
658                        break
659                    raise error, "unknown extension"
660
661        elif this == "^":
662            subpatternappend((AT, AT_BEGINNING))
663
664        elif this == "$":
665            subpattern.append((AT, AT_END))
666
667        elif this and this[0] == "\\":
668            code = _escape(source, this, state)
669            subpatternappend(code)
670
671        else:
672            raise error, "parser error"
673
674    return subpattern
675
676def parse(str, flags=0, pattern=None):
677    # parse 're' pattern into list of (opcode, argument) tuples
678
679    source = Tokenizer(str)
680
681    if pattern is None:
682        pattern = Pattern()
683    pattern.flags = flags
684    pattern.str = str
685
686    p = _parse_sub(source, pattern, 0)
687
688    tail = source.get()
689    if tail == ")":
690        raise error, "unbalanced parenthesis"
691    elif tail:
692        raise error, "bogus characters at end of regular expression"
693
694    if flags & SRE_FLAG_DEBUG:
695        p.dump()
696
697    if not (flags & SRE_FLAG_VERBOSE) and p.pattern.flags & SRE_FLAG_VERBOSE:
698        # the VERBOSE flag was switched on inside the pattern.  to be
699        # on the safe side, we'll parse the whole thing again...
700        return parse(str, p.pattern.flags)
701
702    return p
703
704def parse_template(source, pattern):
705    # parse 're' replacement string into list of literals and
706    # group references
707    s = Tokenizer(source)
708    sget = s.get
709    p = []
710    a = p.append
711    def literal(literal, p=p, pappend=a):
712        if p and p[-1][0] is LITERAL:
713            p[-1] = LITERAL, p[-1][1] + literal
714        else:
715            pappend((LITERAL, literal))
716    sep = source[:0]
717    if type(sep) is type(""):
718        makechar = chr
719    else:
720        makechar = unichr
721    while 1:
722        this = sget()
723        if this is None:
724            break # end of replacement string
725        if this and this[0] == "\\":
726            # group
727            c = this[1:2]
728            if c == "g":
729                name = ""
730                if s.match("<"):
731                    while 1:
732                        char = sget()
733                        if char is None:
734                            raise error, "unterminated group name"
735                        if char == ">":
736                            break
737                        name = name + char
738                if not name:
739                    raise error, "missing group name"
740                try:
741                    index = int(name)
742                    if index < 0:
743                        raise error, "negative group number"
744                except ValueError:
745                    if not isname(name):
746                        raise error, "bad character in group name"
747                    try:
748                        index = pattern.groupindex[name]
749                    except KeyError:
750                        raise IndexError, "unknown group name"
751                a((MARK, index))
752            elif c == "0":
753                if s.next in OCTDIGITS:
754                    this = this + sget()
755                    if s.next in OCTDIGITS:
756                        this = this + sget()
757                literal(makechar(int(this[1:], 8) & 0xff))
758            elif c in DIGITS:
759                isoctal = False
760                if s.next in DIGITS:
761                    this = this + sget()
762                    if (c in OCTDIGITS and this[2] in OCTDIGITS and
763                        s.next in OCTDIGITS):
764                        this = this + sget()
765                        isoctal = True
766                        literal(makechar(int(this[1:], 8) & 0xff))
767                if not isoctal:
768                    a((MARK, int(this[1:])))
769            else:
770                try:
771                    this = makechar(ESCAPES[this][1])
772                except KeyError:
773                    pass
774                literal(this)
775        else:
776            literal(this)
777    # convert template to groups and literals lists
778    i = 0
779    groups = []
780    groupsappend = groups.append
781    literals = [None] * len(p)
782    for c, s in p:
783        if c is MARK:
784            groupsappend((i, s))
785            # literal[i] is already None
786        else:
787            literals[i] = s
788        i = i + 1
789    return groups, literals
790
791def expand_template(template, match):
792    g = match.group
793    sep = match.string[:0]
794    groups, literals = template
795    literals = literals[:]
796    try:
797        for index, group in groups:
798            literals[index] = s = g(group)
799            if s is None:
800                raise error, "unmatched group"
801    except IndexError:
802        raise error, "invalid group reference"
803    return sep.join(literals)
804